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Sample records for vicinus predator started

  1. Predator Arithmetic

    Science.gov (United States)

    Shutler, Paul M. E.; Fong, Ng Swee

    2010-01-01

    Modern Hindu-Arabic numeration is the end result of a long period of evolution, and is clearly superior to any system that has gone before, but is it optimal? We compare it to a hypothetical base 5 system, which we dub Predator arithmetic, and judge which of the two systems is superior from a mathematics education point of view. We find that…

  2. Interstellar Predation

    Science.gov (United States)

    Cockell, C. S.; Lee, M.

    Although chemosynthesis and photosynthesis can theoretically supply enough energy for intelligence, for reasons elucidated here, heterotrophy and specifically phagotrophy (ingestion of prey) are likely to make predation a characteristic of life and extraterrestrial intelligence (ETI). Here, the Earth's biota is used to consider the nature of interstellar predation. The ability of the ETI to directly ingest a biota will be determined by the chiral preference of the ETI, the compatibility of the biochemistry used in life on Earth with the molecules required by the ETI and the potential toxicity of the macromolecules. If chirality is determined by astrophysical factors and not by the specificities of terrestrial origins of life and if molecules found in terrestrial organisms are also represented in ETIs (which could plausibly include hydrated carbohydrides and many amino acids that are similar or identical to amino acids found in meteoritic or cometary material) then the Earth might represent a universally appreciated resource. The Earth's biota could be used as an energy supply or, if other forms of technology have advanced to the point where bioreactors can be exclusively used to supply a civilization with food, as a culinary curiosity. Even in the absence of metabolic compatibility, technology can be used to extract useful products from an undigestible biota, similarly to the industrial biotransformation of cellulose. The value of the resource will also be determined by the availability of prey. Planets at stages in biological evolution where the surface is dominated by just one or several large (>5kg), abundant, easily captured organisms are particu- larly attractive to predators because harvesting techniques can be standardized. We discuss implications for exobiology and the `Fermi Paradox'.

  3. Predation efficiency of Anopheles gambiae larvae by aquatic predators in western Kenya highlands

    Directory of Open Access Journals (Sweden)

    Nyindo Mramba

    2011-07-01

    Full Text Available Abstract Background The current status of insecticide resistance in mosquitoes and the effects of insecticides on non-target insect species have raised the need for alternative control methods for malaria vectors. Predation has been suggested as one of the important regulation mechanisms for malaria vectors in long-lasting aquatic habitats, but the predation efficiency of the potential predators is largely unknown in the highlands of western Kenya. In the current study, we examined the predation efficiency of five predators on Anopheles gambiae s.s larvae in 24 hour and semi- field evaluations. Methods Predators were collected from natural habitats and starved for 12 hours prior to starting experiments. Preliminary experiments were conducted to ascertain the larval stage most predated by each predator species. When each larval instar was subjected to predation, third instar larvae were predated at the highest rate. Third instar larvae of An. gambiae were introduced into artificial habitats with and without refugia at various larval densities. The numbers of surviving larvae were counted after 24 hours in 24. In semi-field experiments, the larvae were counted daily until they were all either consumed or had developed to the pupal stage. Polymerase chain reaction was used to confirm the presence of An. gambiae DNA in predator guts. Results Experiments found that habitat type (P P P P An. gambiae DNA was found in at least three out of ten midguts for all predator species. Gambusia affins was the most efficient, being three times more efficient than tadpoles. Conclusion These experiments provide insight into the efficiency of specific natural predators against mosquito larvae. These naturally occurring predators may be useful in biocontrol strategies for aquatic stage An. gambiae mosquitoes. Further investigations should be done in complex natural habitats for these predators.

  4. Predation and caribou populations

    Directory of Open Access Journals (Sweden)

    Dale R. Seip

    1991-10-01

    Full Text Available Predation, especially wolf (Canis lupus predation, limits many North American caribou (Rangifer tarandus populations below the density that food resources could sustain. The impact of predation depends on the parameters for the functional and numerical response of the wolves, relative to the potential annual increment of the caribou population. Differences in predator-avoidance strategies largely explain the major differences in caribou densities that occur naturally in North America. Caribou migrations that spatially separate caribou from wolves allow relatively high densities of caribou to survive. Non-migratory caribou that live in areas where wolf populations are sustained by alternate prey can be eliminated by wolf predation.

  5. Birds as predators in tropical agroforestry systems.

    Science.gov (United States)

    Van Bael, Sunshine A; Philpott, Stacy M; Greenberg, Russell; Bichier, Peter; Barber, Nicholas A; Mooney, Kailen A; Gruner, Daniel S

    2008-04-01

    Insectivorous birds reduce arthropod abundances and their damage to plants in some, but not all, studies where predation by birds has been assessed. The variation in bird effects may be due to characteristics such as plant productivity or quality, habitat complexity, and/or species diversity of predator and prey assemblages. Since agroforestry systems vary in such characteristics, these systems provide a good starting point for understanding when and where we can expect predation by birds to be important. We analyze data from bird exclosure studies in forests and agroforestry systems to ask whether birds consistently reduce their arthropod prey base and whether bird predation differs between forests and agroforestry systems. Further, we focus on agroforestry systems to ask whether the magnitude of bird predation (1) differs between canopy trees and understory plants, (2) differs when migratory birds are present or absent, and (3) correlates with bird abundance and diversity. We found that, across all studies, birds reduce all arthropods, herbivores, carnivores, and plant damage. We observed no difference in the magnitude of bird effects between agroforestry systems and forests despite simplified habitat structure and plant diversity in agroforests. Within agroforestry systems, bird reduction of arthropods was greater in the canopy than the crop layer. Top-down effects of bird predation were especially strong during censuses when migratory birds were present in agroforestry systems. Importantly, the diversity of the predator assemblage correlated with the magnitude of predator effects; where the diversity of birds, especially migratory birds, was greater, birds reduced arthropod densities to a greater extent. We outline potential mechanisms for relationships between bird predator, insect prey, and habitat characteristics, and we suggest future studies using tropical agroforests as a model system to further test these areas of ecological theory.

  6. to start

    Indian Academy of Sciences (India)

    Click here to start. Table of contents. Slide 1 · Slide 2 · Slide 3 · Slide 4 · Slide 5 · Slide 6 · Slide 7 · Slide 8 · Slide 9 · Slide 10 · Slide 11 · Slide 12 · Slide 13 · Slide 14 · Slide 15 · Slide 16 · Slide 17 · Slide 18 · Slide 19.

  7. Press Start

    Science.gov (United States)

    Harteveld, Casper

    This level sets the stage for the design philosophy called “Triadic Game Design” (TGD). This design philosophy can be summarized with the following sentence: it takes two to tango, but it takes three to design a meaningful game or a game with a purpose. Before the philosophy is further explained, this level will first delve into what is meant by a meaningful game or a game with a purpose. Many terms and definitions have seen the light and in this book I will specifically orient at digital games that aim to have an effect beyond the context of the game itself. Subsequently, a historical overview is given of the usage of games with a serious purpose which starts from the moment we human beings started to walk on our feet till our contemporary society. It turns out that we have been using games for all kinds of non-entertainment purposes for already quite a long time. With this introductory material in the back of our minds, I will explain the concept of TGD by means of a puzzle. After that, the protagonist of this book, the game Levee Patroller, is introduced. Based on the development of this game, the idea of TGD, which stresses to balance three different worlds, the worlds of Reality, Meaning, and Play, came into being. Interested? Then I suggest to quickly “press start!”

  8. to start

    Indian Academy of Sciences (India)

    Click here to start. Table of contents. Slide 1 · Slide 2 · Slide 3 · Slide 4 · Slide 5 · Slide 6 · Slide 7 · Slide 8 · Slide 9 · Slide 10 · Slide 11 · Slide 12 · Slide 13 · Slide 14 · Slide 15 · Slide 16 · Slide 17 · Slide 18 · Slide 19 · Slide 20 · Slide 21 · Slide 22 · Slide 23 · Slide 24 · Slide 25 · Slide 26 · Slide 27 · Slide 28 · Slide 29 · Slide 30.

  9. Starting electronics

    CERN Document Server

    Brindley, Keith

    2005-01-01

    Starting Electronics is unrivalled as a highly practical introduction for hobbyists, students and technicians. Keith Brindley introduces readers to the functions of the main component types, their uses, and the basic principles of building and designing electronic circuits. Breadboard layouts make this very much a ready-to-run book for the experimenter; and the use of multimeter, but not oscilloscopes, puts this practical exploration of electronics within reach of every home enthusiast's pocket. The third edition has kept the simplicity and clarity of the original. New material

  10. Predator identity can explain nest predation patterns. Chapter 11

    Science.gov (United States)

    Jennifer L. Reidy; Frank R., III Thompson

    2012-01-01

    Knowledge of dominant predators is necessary to identify predation patterns and mitigate losses to nest predation, especially for endangered songbirds. We monitored songbird nests with timelapse infrared video cameras at Fort Hood Military Reservation, Texas, from 1997 to 2002 and 2005, and in Austin, Texas, during 2005, 2006, 2008, and 2009. Predation was the most...

  11. The Predator-Prey Relationship

    Science.gov (United States)

    Mitchell, Charles W.

    1977-01-01

    Many children develop a mistaken attitude about the predator-prey relationship in the ecosystem. Fairy tales portray the predator as evil or worthless. This article attempts to clarify the role of the predator by giving numerous examples of the value of predators. (MA)

  12. Predator avoidance by nauplii

    DEFF Research Database (Denmark)

    Titelman, Josefin; Kiørboe, Thomas

    2003-01-01

    upwards and also away from the flow, and are thus able to assess direction of flow. Sensitivity to hydrodynamic signals is tightly linked to the general motility pattern. Hydrodynamically conspicuous nauplii that move in a jump-sink pattern are more effective at remotely detecting predators than...... are continuous swimmers of similar size. We assessed the effects of different motility strategies in terms of detectability and volume encounter with copepod predators by means of simple hydrodynamic models. While jump-sink type nauplii may be at an advantage over swimmers in interactions with sinking...

  13. Production of coleopteran predators

    Science.gov (United States)

    The research literature reveals moderate advances in technology to produce coleopteran predators especially lady beetles. We have several factitious prey/foods and insect-free artificial diets for polyphagous species. It might be more time and cost effective to develop artificial diet-based producti...

  14. The Starting Early Starting Smart Story.

    Science.gov (United States)

    Casey Family Programs, Seattle, WA.

    Starting Early Starting Smart (SESS) is an early childhood public/private initiative designed to identify new, empirical knowledge about the effectiveness of integrating substance abuse prevention, addictions treatment, and mental health services with primary health care and childcare service settings (e.g., Head Start, day care, preschool) to…

  15. Understanding predation: implications toward forest management

    Science.gov (United States)

    Harvey R. Smith

    1991-01-01

    It is generally accepted that when gypsy moths rest in the litter survival is low due to predation by ground-foraging generalist predators and that predation can maintain these populations indefinitely. Forest Service research on predators of gypsy moth continues to focus on population dynamics, the mechanisms of predation and forest management implications.

  16. Bat predation by spiders.

    Directory of Open Access Journals (Sweden)

    Martin Nyffeler

    Full Text Available In this paper more than 50 incidences of bats being captured by spiders are reviewed. Bat-catching spiders have been reported from virtually every continent with the exception of Antarctica (≈ 90% of the incidences occurring in the warmer areas of the globe between latitude 30° N and 30° S. Most reports refer to the Neotropics (42% of observed incidences, Asia (28.8%, and Australia-Papua New Guinea (13.5%. Bat-catching spiders belong to the mygalomorph family Theraphosidae and the araneomorph families Nephilidae, Araneidae, and Sparassidae. In addition to this, an attack attempt by a large araneomorph hunting spider of the family Pisauridae on an immature bat was witnessed. Eighty-eight percent of the reported incidences of bat catches were attributable to web-building spiders and 12% to hunting spiders. Large tropical orb-weavers of the genera Nephila and Eriophora in particular have been observed catching bats in their huge, strong orb-webs (of up to 1.5 m diameter. The majority of identifiable captured bats were small aerial insectivorous bats, belonging to the families Vespertilionidae (64% and Emballonuridae (22% and usually being among the most common bat species in their respective geographic area. While in some instances bats entangled in spider webs may have died of exhaustion, starvation, dehydration, and/or hyperthermia (i.e., non-predation death, there were numerous other instances where spiders were seen actively attacking, killing, and eating the captured bats (i.e., predation. This evidence suggests that spider predation on flying vertebrates is more widespread than previously assumed.

  17. Bat Predation by Spiders

    Science.gov (United States)

    Nyffeler, Martin; Knörnschild, Mirjam

    2013-01-01

    In this paper more than 50 incidences of bats being captured by spiders are reviewed. Bat-catching spiders have been reported from virtually every continent with the exception of Antarctica (∼90% of the incidences occurring in the warmer areas of the globe between latitude 30° N and 30° S). Most reports refer to the Neotropics (42% of observed incidences), Asia (28.8%), and Australia-Papua New Guinea (13.5%). Bat-catching spiders belong to the mygalomorph family Theraphosidae and the araneomorph families Nephilidae, Araneidae, and Sparassidae. In addition to this, an attack attempt by a large araneomorph hunting spider of the family Pisauridae on an immature bat was witnessed. Eighty-eight percent of the reported incidences of bat catches were attributable to web-building spiders and 12% to hunting spiders. Large tropical orb-weavers of the genera Nephila and Eriophora in particular have been observed catching bats in their huge, strong orb-webs (of up to 1.5 m diameter). The majority of identifiable captured bats were small aerial insectivorous bats, belonging to the families Vespertilionidae (64%) and Emballonuridae (22%) and usually being among the most common bat species in their respective geographic area. While in some instances bats entangled in spider webs may have died of exhaustion, starvation, dehydration, and/or hyperthermia (i.e., non-predation death), there were numerous other instances where spiders were seen actively attacking, killing, and eating the captured bats (i.e., predation). This evidence suggests that spider predation on flying vertebrates is more widespread than previously assumed. PMID:23516436

  18. Sharks modulate their escape behavior in response to predator size, speed and approach orientation.

    Science.gov (United States)

    Seamone, Scott; Blaine, Tristan; Higham, Timothy E

    2014-12-01

    Escape responses are often critical for surviving predator-prey interactions. Nevertheless, little is known about how predator size, speed and approach orientation impact escape performance, especially in larger prey that are primarily viewed as predators. We used realistic shark models to examine how altering predatory behavior and morphology (size, speed and approach orientation) influences escape behavior and performance in Squalus acanthias, a shark that is preyed upon by apex marine predators. Predator models induced C-start escape responses, and increasing the size and speed of the models triggered a more intense response (increased escape turning rate and acceleration). In addition, increased predator size resulted in greater responsiveness from the sharks. Among the responses, predator approach orientation had the most significant impact on escapes, such that the head-on approach, as compared to the tail-on approach, induced greater reaction distances and increased escape turning rate, speed and acceleration. Thus, the anterior binocular vision in sharks renders them less effective at detecting predators approaching from behind. However, it appears that sharks compensate by performing high-intensity escapes, likely induced by the lateral line system, or by a sudden visual flash of the predator entering their field of view. Our study reveals key aspects of escape behavior in sharks, highlighting the modulation of performance in response to predator approach. Copyright © 2014 Elsevier GmbH. All rights reserved.

  19. Can cat predation help competitors coexist in seabird communities?

    Science.gov (United States)

    Pontier, Dominique; Fouchet, David; Bried, Joël

    2010-01-07

    On oceanic islands, nest site availability can be an important factor regulating seabird population dynamics. The potential for birds to secure a nest to reproduce can be an important component of their life histories. The dates at which different seabird species arrive at colonies to breed will have important consequences for their relative chances of success. Early arrival on the island allows birds to obtain nests more easily and have higher reproductive success. However, the presence of an introduced predator may reverse this situation. For instance, in the sub-Antarctic Kerguelen archipelago, early arriving birds suffer heavy predation from introduced cats. Cats progressively switch from seabirds to rabbits, since the local rabbit population starts to peak after early arriving seabird species have already returned to the colony. When late-arriving birds arrive, cat predation pressure on seabirds is thus weaker. In this paper, we investigate the assumption that the advantage of early nest mnopolization conferred to early arriving birds may be counterbalanced by the cost resulting from predation. We develop a mathematical model representing a simplified situation in which two insular seabird species differ only in their arrival date at the colony site and compete for nesting sites. We conclude that predation may ensure the coexistence of the two bird species or favor the late-arriving species, but only when seasonal variations in predation pressure are large. Interestingly, we conclude that arriving early is only favorable until a given level where high reproductive success no longer compensates for the long exposure to strong predation pressure. Our work suggests that predation can help to maintain the balance between species of different phenologies.

  20. Is prey predation risk influenced more by increasing predator density or predator species richness in stream enclosures?

    Science.gov (United States)

    Vance-Chalcraft, Heather D; Soluk, Daniel A; Ozburn, Nicholas

    2004-03-01

    The direct lethal impacts and the indirect effects predators have on prey characteristics, such as behavior, have fitness consequences for the prey. Whether the level of predation risk that prey face in the presence of multiple predator species can be predicted from a null model that sums the risk from each predator species in isolation is unclear. In field enclosures, we tested whether the predation risk experienced by Stenonema mayfly larvae from a dragonfly larva ( Boyeria vinosa) and a hellgrammite ( Corydalus cornutus) together matched the predictions of the multiplicative risk model. We then compared whether any deviations from the model's predictions were larger in the presence of two predator species than in the presence of an equivalent density of individuals from either predator species alone, to determine if unique effects arise for the prey in the presence of multiple predator species. We also determined if prey moved preferentially into predator-free refuge spaces or decreased their movement in the presence of predators. Stenonema's risk of predation was reduced compared to the model's prediction, but no unique multiple predator species effects were present because this risk reduction was comparable in magnitude to the level exhibited in the presence of each predator species alone. The prey did not move into predator-free refuge spaces in the presence of predators in the field enclosures. Thus, these predators appear to interfere interspecifically and intraspecifically, which may facilitate the coexistence of the predators and the prey.

  1. Predator behaviour and predation risk in the heterogeneous Arctic environment.

    Science.gov (United States)

    Lecomte, Nicolas; Careau, Vincent; Gauthier, Gilles; Giroux, Jean-François

    2008-05-01

    1. Habitat heterogeneity and predator behaviour can strongly affect predator-prey interactions but these factors are rarely considered simultaneously, especially when systems encompass multiple predators and prey. 2. In the Arctic, greater snow geese Anser caerulescens atlanticus L. nest in two structurally different habitats: wetlands that form intricate networks of water channels, and mesic tundra where such obstacles are absent. In this heterogeneous environment, goose eggs are exposed to two types of predators: the arctic fox Vulpes lagopus L. and a diversity of avian predators. We hypothesized that, contrary to birds, the hunting ability of foxes would be impaired by the structurally complex wetland habitat, resulting in a lower predation risk for goose eggs. 3. In addition, lemmings, the main prey of foxes, show strong population cycles. We thus further examined how their fluctuations influenced the interaction between habitat heterogeneity and fox predation on goose eggs. 4. An experimental approach with artificial nests suggested that foxes were faster than avian predators to find unattended goose nests in mesic tundra whereas the reverse was true in wetlands. Foxes spent 3.5 times more time between consecutive attacks on real goose nests in wetlands than in mesic tundra. Their attacks on goose nests were also half as successful in wetlands than in mesic tundra whereas no difference was found for avian predators. 5. Nesting success in wetlands (65%) was higher than in mesic tundra (56%) but the difference between habitats increased during lemming crashes (15%) compared to other phases of the cycle (5%). Nests located at the edge of wetland patches were also less successful than central ones, suggesting a gradient in accessibility of goose nests in wetlands for foxes. 6. Our study shows that the structural complexity of wetlands decreases predation risk from foxes but not avian predators in arctic-nesting birds. Our results also demonstrate that cyclic

  2. Intraguild predation in pioneer predator communities of alpine glacier forelands.

    Science.gov (United States)

    Raso, Lorna; Sint, Daniela; Mayer, Rebecca; Plangg, Simon; Recheis, Thomas; Brunner, Silvia; Kaufmann, Rüdiger; Traugott, Michael

    2014-08-01

    Pioneer communities establishing themselves in the barren terrain in front of glacier forelands consist principally of predator species such as carabid beetles and lycosid spiders. The fact that so many different predators can co-inhabit an area with no apparent primary production was initially explained by allochthonous material deposited in these forelands. However, whether these populations can be sustained on allochthonous material alone is questionable and recent studies point towards this assumption to be flawed. Intraguild predation (IGP) might play an important role in these pioneer predator assemblages, especially in the very early successional stages where other prey is scarce. Here, we investigated IGP between the main predator species and their consumption of Collembola, an important autochthonous alternative prey, within a glacier foreland in the Ötztal (Austrian Alps). Multiplex PCR and stable isotope analysis were used to characterize the trophic niches in an early and late pioneer stage over 2 years. Results showed that intraguild prey was consumed by all invertebrate predators, particularly the larger carabid species. Contrary to our initial hypothesis, the DNA detection frequency of IGP prey was not significantly higher in early than in late pioneer stage, which was corroborated by the stable isotope analysis. Collembola were the most frequently detected prey in all of the predators, and the overall prey DNA detection patterns were consistent between years. Our findings show that IGP appears as a constant in these pioneer predator communities and that it remains unaffected by successional changes. © 2014 The Authors. Molecular Ecology Published by John Wiley & Sons Ltd.

  3. Ocean acidification alters predator behaviour and reduces predation rate.

    Science.gov (United States)

    Watson, Sue-Ann; Fields, Jennifer B; Munday, Philip L

    2017-02-01

    Ocean acidification poses a range of threats to marine invertebrates; however, the emerging and likely widespread effects of rising carbon dioxide (CO 2 ) levels on marine invertebrate behaviour are still little understood. Here, we show that ocean acidification alters and impairs key ecological behaviours of the predatory cone snail Conus marmoreus Projected near-future seawater CO 2 levels (975 µatm) increased activity in this coral reef molluscivore more than threefold (from less than 4 to more than 12 mm min -1 ) and decreased the time spent buried to less than one-third when compared with the present-day control conditions (390 µatm). Despite increasing activity, elevated CO 2 reduced predation rate during predator-prey interactions with control-treated humpbacked conch, Gibberulus gibberulus gibbosus; 60% of control predators successfully captured and consumed their prey, compared with only 10% of elevated CO 2 predators. The alteration of key ecological behaviours of predatory invertebrates by near-future ocean acidification could have potentially far-reaching implications for predator-prey interactions and trophic dynamics in marine ecosystems. Combined evidence that the behaviours of both species in this predator-prey relationship are altered by elevated CO 2 suggests food web interactions and ecosystem structure will become increasingly difficult to predict as ocean acidification advances over coming decades. © 2017 The Author(s).

  4. FINANCIRANJE START - UP PODJETIJ

    OpenAIRE

    Kraner, Simona

    2016-01-01

    V magistrskem delu ugotavljamo specifike start-up podjetij ter njihov vpliv na dostopnost in primernost posameznih virov financiranja. Ko ugotovimo in razdelamo poglavitne specifike, ki na splošno veljajo za start-up podjetja, se lotimo proučevanja faz financiranja, skozi katera start-up prehajajo. Vsako od sedmih tipičnih faz financiranja start-up podjetij opredelimo z vidika značilnosti, ki za start-up podjetja v specifični razvojni fazi veljajo. Prvo polovico teoretičnega dela zaključi...

  5. Predation of freshwater fish in environments with elevated carbon dioxide

    Science.gov (United States)

    Midway, Stephen R.; Hasler, Caleb T.; Wagner, Tyler; Suski, Cory D.

    2017-01-01

    Carbon dioxide (CO2) in fresh-water environments is poorly understood, yet in marine environments CO2 can affect fish behaviour, including predator–prey relationships. To examine changes in predator success in elevated CO2, we experimented with predatory Micropterus salmoides and Pimephales promelas prey. We used a two-factor fully crossed experimental design; one factor was 4-day (acclimation) CO2 concentration and the second factor CO2 concentration during 20-min predation experiments. Both factors had three treatment levels, including ambient partial pressure of CO2(pCO2; 0–1000 μatm), low pCO2 (4000–5000 μatm) and high pCO2 (8000–10 000 μatm). Micropterus salmoides was exposed to both factors, whereas P. promelas was not exposed to the acclimation factor. In total, 83 of the 96 P. promelas were consumed (n = 96 trials) and we saw no discernible effect of CO2 on predator success or time to predation. Failed strikes and time between failed strikes were too infrequent to model. Compared with marine systems, our findings are unique in that we not only saw no changes in prey capture success with increasing CO2, but we also used CO2 treatments that were substantially higher than those in past experiments. Our work demonstrated a pronounced resiliency of freshwater predators to elevated CO2 exposure, and a starting point for future work in this area.

  6. Predator control problems in Alaska

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — One of the important wildlife management activities in Alaska is that of predator control. This simple statement requires some explanation. In the course of these...

  7. Predation on Japanese quail vs. house sparrow eggs in artificial nests: small eggs reveal small predators

    Science.gov (United States)

    Thomas J. Maier; Richard M. DeGraaf

    2000-01-01

    Nest predation studies frequently use eggs such as Japanese Quail (Coturnix japonica) to identify potential predators of Neotropical migrants' eggs, but such eggs may be too large or thick-shelled to identify the full complement of potential predators. We compared predation events and predators of Japanese Quail and smaller House Sparrow (

  8. Engine Cold Start

    Science.gov (United States)

    2015-09-01

    UNCLASSIFIED UNCLASSIFIED ENGINE COLD START INTERIM REPORT TFLRF No. 469 by Douglas M. Yost Gregory A. T. Hansen U.S...not return it to the originator. UNCLASSIFIED UNCLASSIFIED ENGINE COLD START INTERIM REPORT TFLRF No. 469 by Douglas M. Yost...TITLE AND SUBTITLE Engine Cold Start 5a. CONTRACT NUMBER W56HZV-09-C-0100 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Douglas

  9. Subsidized predators and imperiled prey: the impact of avian predators on salmonids

    OpenAIRE

    Osterback, Ann-Marie Kristina

    2014-01-01

    Generalist predators can alter or limit the survival of individuals and the dynamics of populations, especially for imperiled prey. The effects of predation can be further exacerbated if anthropogenic subsidies provide novel food sources to predators that decouple predator-prey dynamics and contribute to extinction risk of native prey. However, quantifying predation rates on rare prey is challenging; as is identifying shifts in predator diet and resource use over time. For my research, I deve...

  10. Head Start in Action.

    Science.gov (United States)

    Riley, Clara M. D.; Epps, Frances M. J.

    Records and observations from a summer Head Start program, conducted in Los Angeles by Delta Sigma Theta, are delineated in this book. It relates firsthand experiences of the participating personnel as they developed and implemented a Head Start program for some 300 children. The book is divided into three sections. Section I,…

  11. Lean start-up

    DEFF Research Database (Denmark)

    Rasmussen, Erik Stavnsager; Tanev, Stoyan

    2016-01-01

    The risk of launching new products and starting new firms is known to be extremely high. The Lean Start-up approach is a way of reducing these risks and enhancing the chances for success by validating the products and services in the market with customers before launching it in full scale. The main...... and the final business model. In other words: The start-up must first nail the problem together with the customers, then develop the solution and test, and then in the end scale it to a full-grown business model....

  12. Selective Predation of a Stalking Predator on Ungulate Prey.

    Science.gov (United States)

    Heurich, Marco; Zeis, Klara; Küchenhoff, Helmut; Müller, Jörg; Belotti, Elisa; Bufka, Luděk; Woelfing, Benno

    2016-01-01

    Prey selection is a key factor shaping animal populations and evolutionary dynamics. An optimal forager should target prey that offers the highest benefits in terms of energy content at the lowest costs. Predators are therefore expected to select for prey of optimal size. Stalking predators do not pursue their prey long, which may lead to a more random choice of prey individuals. Due to difficulties in assessing the composition of available prey populations, data on prey selection of stalking carnivores are still scarce. We show how the stalking predator Eurasian lynx (Lynx lynx) selects prey individuals based on species identity, age, sex and individual behaviour. To address the difficulties in assessing prey population structure, we confirm inferred selection patterns by using two independent data sets: (1) data of 387 documented kills of radio-collared lynx were compared to the prey population structure retrieved from systematic camera trapping using Manly's standardized selection ratio alpha and (2) data on 120 radio-collared roe deer were analysed using a Cox proportional hazards model. Among the larger red deer prey, lynx selected against adult males-the largest and potentially most dangerous prey individuals. In roe deer lynx preyed selectively on males and did not select for a specific age class. Activity during high risk periods reduced the risk of falling victim to a lynx attack. Our results suggest that the stalking predator lynx actively selects for size, while prey behaviour induces selection by encounter and stalking success rates.

  13. Selective Predation of a Stalking Predator on Ungulate Prey.

    Directory of Open Access Journals (Sweden)

    Marco Heurich

    Full Text Available Prey selection is a key factor shaping animal populations and evolutionary dynamics. An optimal forager should target prey that offers the highest benefits in terms of energy content at the lowest costs. Predators are therefore expected to select for prey of optimal size. Stalking predators do not pursue their prey long, which may lead to a more random choice of prey individuals. Due to difficulties in assessing the composition of available prey populations, data on prey selection of stalking carnivores are still scarce. We show how the stalking predator Eurasian lynx (Lynx lynx selects prey individuals based on species identity, age, sex and individual behaviour. To address the difficulties in assessing prey population structure, we confirm inferred selection patterns by using two independent data sets: (1 data of 387 documented kills of radio-collared lynx were compared to the prey population structure retrieved from systematic camera trapping using Manly's standardized selection ratio alpha and (2 data on 120 radio-collared roe deer were analysed using a Cox proportional hazards model. Among the larger red deer prey, lynx selected against adult males-the largest and potentially most dangerous prey individuals. In roe deer lynx preyed selectively on males and did not select for a specific age class. Activity during high risk periods reduced the risk of falling victim to a lynx attack. Our results suggest that the stalking predator lynx actively selects for size, while prey behaviour induces selection by encounter and stalking success rates.

  14. Early Head Start Evaluation

    Data.gov (United States)

    U.S. Department of Health & Human Services — Longitudinal information from an evaluation where children were randomly assigned to Early Head Start or community services as usual;direct assessments and...

  15. Head Start Impact Study

    Data.gov (United States)

    U.S. Department of Health & Human Services — Nationally representative, longitudinal information from an evaluation where children were randomly assigned to Head Start or community services as usual;direct...

  16. FEMA DFIRM Station Start

    Data.gov (United States)

    Minnesota Department of Natural Resources — This table contains information about station starting locations. These locations indicate the reference point that was used as the origin for distance measurements...

  17. Getting started with Unity

    CERN Document Server

    Felicia, Patrick

    2013-01-01

    Getting Started with Unity is written in an easy-to-follow tutorial format.""Getting Started with Unity"" is for[ 3D game developers[/color] who would like to learn how to use Unity3D and become familiar with its core features. This book is also suitable for intermediate users who would like to improve their skills. No prior knowledge of Unity3D is required.

  18. A Generalist Protist Predator Enables Coexistence in Multitrophic Predator-Prey Systems Containing a Phage and the Bacterial Predator Bdellovibrio

    Directory of Open Access Journals (Sweden)

    Julia Johnke

    2017-10-01

    Full Text Available Complex ecosystems harbor multiple predators and prey species whose direct and indirect interactions are under study. In particular, the combined effects of predator diversity and resource preference on prey removal are not known. To understand the effect of interspecies interactions, combinations of micro-predators—i.e., protists (generalists, predatory bacteria (semi-specialists, and phages (specialists—and bacterial prey were tracked over a 72-h period in miniature membrane bioreactors. While specialist predators alone drove their preferred prey to extinction, the inclusion of a generalist resulted in uniform losses among prey species. Most importantly, presence of a generalist predator enabled coexistence of all predators and prey. As the generalist predator also negatively affected the other predators, we suggest that resource partitioning between predators and the constant availability of resources for bacterial growth due to protist predation stabilizes the system and keeps its diversity high. The appearance of resistant prey strains and subsequent evolution of specialist predators unable to infect the ancestral prey implies that multitrophic communities are able to persist and stabilize themselves. Interestingly, the appearance of BALOs and phages unable to infect their prey was only observed for the BALO or phage in the absence of additional predators or prey species indicating that competition between predators might influence coevolutionary dynamics.

  19. Predators and the public trust.

    Science.gov (United States)

    Treves, Adrian; Chapron, Guillaume; López-Bao, Jose V; Shoemaker, Chase; Goeckner, Apollonia R; Bruskotter, Jeremy T

    2017-02-01

    Many democratic governments recognize a duty to conserve environmental resources, including wild animals, as a public trust for current and future citizens. These public trust principles have informed two centuries of U.S.A. Supreme Court decisions and environmental laws worldwide. Nevertheless numerous populations of large-bodied, mammalian carnivores (predators) were eradicated in the 20th century. Environmental movements and strict legal protections have fostered predator recoveries across the U.S.A. and Europe since the 1970s. Now subnational jurisdictions are regaining management authority from central governments for their predator subpopulations. Will the history of local eradication repeat or will these jurisdictions adopt public trust thinking and their obligation to broad public interests over narrower ones? We review the role of public trust principles in the restoration and preservation of controversial species. In so doing we argue for the essential roles of scientists from many disciplines concerned with biological diversity and its conservation. We look beyond species endangerment to future generations' interests in sustainability, particularly non-consumptive uses. Although our conclusions apply to all wild organisms, we focus on predators because of the particular challenges they pose for government trustees, trust managers, and society. Gray wolves Canis lupus L. deserve particular attention, because detailed information and abundant policy debates across regions have exposed four important challenges for preserving predators in the face of interest group hostility. One challenge is uncertainty and varied interpretations about public trustees' responsibilities for wildlife, which have created a mosaic of policies across jurisdictions. We explore how such mosaics have merits and drawbacks for biodiversity. The other three challenges to conserving wildlife as public trust assets are illuminated by the biology of predators and the interacting

  20. Intraguild predation and native lady beetle decline.

    Science.gov (United States)

    Gardiner, Mary M; O'Neal, Matthew E; Landis, Douglas A

    2011-01-01

    Coccinellid communities across North America have experienced significant changes in recent decades, with declines in several native species reported. One potential mechanism for these declines is interference competition via intraguild predation; specifically, increased predation of native coccinellid eggs and larvae following the introduction of exotic coccinellids. Our previous studies have shown that agricultural fields in Michigan support a higher diversity and abundance of exotic coccinellids than similar fields in Iowa, and that the landscape surrounding agricultural fields across the north central U.S. influences the abundance and activity of coccinellid species. The goal of this study was to quantify the amount of egg predation experienced by a native coccinellid within Michigan and Iowa soybean fields and explore the influence of local and large-scale landscape structure. Using the native lady beetle Coleomegilla maculata as a model, we found that sentinel egg masses were subject to intense predation within both Michigan and Iowa soybean fields, with 60.7% of egg masses attacked and 43.0% of available eggs consumed within 48 h. In Michigan, the exotic coccinellids Coccinella septempunctata and Harmonia axyridis were the most abundant predators found in soybean fields whereas in Iowa, native species including C. maculata, Hippodamia parenthesis and the soft-winged flower beetle Collops nigriceps dominated the predator community. Predator abundance was greater in soybean fields within diverse landscapes, yet variation in predator numbers did not influence the intensity of egg predation observed. In contrast, the strongest predictor of native coccinellid egg predation was the composition of edge habitats bordering specific fields. Field sites surrounded by semi-natural habitats including forests, restored prairies, old fields, and pasturelands experienced greater egg predation than fields surrounded by other croplands. This study shows that intraguild

  1. Learned predation risk management by spider mites

    Directory of Open Access Journals (Sweden)

    Thomas eHackl

    2014-09-01

    Full Text Available Predation is a prime selective force shaping prey behavior. Investment in anti-predator behavior is traded-off against time and energy for other fitness-enhancing activities such as foraging or reproduction. To optimize this benefit/cost trade-off, prey should be able to innately and/or by experience modulate their behavior to the level of predation risk. Here, we assessed learned predation risk management in the herbivorous two-spotted spider mite Tetranychus urticae. We exposed spider mites coming from benign (naïve or high immediate predation risk (experienced environments to latent and/or no risk and assessed their site choice, activity and oviposition. Benign environments were characterized by the absence of any predator cues, high immediate risk environments by killed spider mites, physical presence of the predatory mite Phytoseiulus persimilis and associated chemosensory traces left on the surface, and latent risk environments by only predator traces. In the no-choice experiment both naïve and experienced spider mites laid their first egg later on leaves with than without predator traces. Irrespective of predator traces presence/absence, experienced mites laid their first egg earlier than naïve ones did. Naïve spider mites were more active, indicating higher restlessness, and laid fewer eggs on leaves with predator traces, whereas experienced mites were less active and laid similar numbers of eggs on leaves with and without predator traces. In the choice experiment both naïve and experienced spider mites preferentially resided and oviposited on leaves without predator traces but experienced mites were less active than naïve ones. Overall, our study suggests that spider mites experienced with high predation risk behave bolder under latent risk than naïve spider mites. Since predator traces alone do not indicate immediate risk, we argue that the attenuated anti-predator response of experienced spider mites represents adaptive learned

  2. Predation risk increases dispersal distance in prey

    Science.gov (United States)

    Otsuki, Hatsune; Yano, Shuichi

    2014-06-01

    Understanding the ecological factors that affect dispersal distances allows us to predict the consequences of dispersal. Although predator avoidance is an important cause of prey dispersal, its effects on dispersal distance have not been investigated. We used simple experimental setups to test dispersal distances of the ambulatory dispersing spider mite ( Tetranychus kanzawai) in the presence or absence of a predator ( Neoseiulus womersleyi). In the absence of predators, most spider mites settled in adjacent patches, whereas the majority of those dispersing in the presence of predators passed through adjacent patches and settled in distant ones. This is the first study to experimentally demonstrate that predators induce greater dispersal distance in prey.

  3. ATLAS starts moving in

    CERN Multimedia

    2004-01-01

    The first large active detector component was lowered into the ATLAS cavern on 1 March. It consisted of the 8 modules forming the lower part of the central barrel of the tile hadronic calorimeter. The work of assembling the barrel, which comprises 64 modules, started the following day.

  4. Jump Starting Entrepreneurship

    DEFF Research Database (Denmark)

    Burcharth, Ana Luiza Lara De Araújo; Smith, Pernille; Frederiksen, Lars

    -hanging opportunity seeking entrepreneurs”, and 3) the “jump-start entrepreneurs”. Whereas the two first categories could be expected, the third one shows that, despite hesitance to be self-employed, being uneasy with it, risk adverse and having strong identification to the previous organization, these entrepreneurs...

  5. Waco Head Start Program.

    Science.gov (United States)

    Porter, Para

    The Economic Opportunity Act of 1964 led to the formation of three separate Head Start Programs in Waco, Texas. The first year, 1,500 children were involved. Of these, 40 percent were Negro, 30 percent Latin American, and 30 percent white. All teachers received a week of preparatory study at the University of Texas. The program involved four areas…

  6. Starting up the upstarts.

    Science.gov (United States)

    Greene, J

    1997-12-20

    Venture capitalists pour $1 billion a year into health care--and that investment may be the most overlooked indicator of new business opportunities. Signs show that companies focused on consolidation and cost-cutting are off the A list for risk capital. Instead, venture capitalists are targeting start-ups that save money on the front lines by truly managing care.

  7. Getting started with UDOO

    CERN Document Server

    Palazzetti, Emanuele

    2015-01-01

    If you are an Android developer who wants to learn how to use UDOO to build Android applications that are capable of interacting with their surrounding environment, then this book is ideal for you. Learning UDOO is the next great step to start building your first real-world prototypes powered by the Android operating system.

  8. Getting started with Go

    CERN Multimedia

    CERN. Geneva

    2015-01-01

    No, not the Chinese boardgame, the programming language that ironically Google made difficult to google for. You may have heard of Golang, and are wondering whether you should learn it. The answer is that of course you should, and this talk should explain why and point you at the best resources to get started.

  9. Invasive predators and global biodiversity loss.

    Science.gov (United States)

    Doherty, Tim S; Glen, Alistair S; Nimmo, Dale G; Ritchie, Euan G; Dickman, Chris R

    2016-10-04

    Invasive species threaten biodiversity globally, and invasive mammalian predators are particularly damaging, having contributed to considerable species decline and extinction. We provide a global metaanalysis of these impacts and reveal their full extent. Invasive predators are implicated in 87 bird, 45 mammal, and 10 reptile species extinctions-58% of these groups' contemporary extinctions worldwide. These figures are likely underestimated because 23 critically endangered species that we assessed are classed as "possibly extinct." Invasive mammalian predators endanger a further 596 species at risk of extinction, with cats, rodents, dogs, and pigs threatening the most species overall. Species most at risk from predators have high evolutionary distinctiveness and inhabit insular environments. Invasive mammalian predators are therefore important drivers of irreversible loss of phylogenetic diversity worldwide. That most impacted species are insular indicates that management of invasive predators on islands should be a global conservation priority. Understanding and mitigating the impact of invasive mammalian predators is essential for reducing the rate of global biodiversity loss.

  10. [Explicit model for searching behavior of predator].

    Science.gov (United States)

    Tiutiunov, Iu V; Sapukhina, N Iu; Senina, I N; Arditi, R

    2002-01-01

    The authors present an approach for explicit modeling of spatio-temporal dynamics of predator-prey community. This approach is based on a reaction-diffusion-adjection PD (prey dependent) system. Local kinetics of population is determined by logistic reproduction function of prey, constant natural mortality of predator and Holling type 2 trophic function. Searching behavior of predator is described by the advective term in predator balance equation assuming the predator acceleration to be proportional to the prey density gradient. The model was studied with zero-flux boundary conditions. The influence of predator searching activity on the community dynamics, in particular, on the emergence of spatial heterogeneity, has been investigated by linear analysis and numerical simulations. It has been shown how searching activity may effect the persistence of species, stabilizing predator-prey interactions at very low level of pest density. It has been demonstrated that obtaining of such dynamic regimes does not require the use of complex trophic functions.

  11. Cannibalism and intraguild predation of eggs within a diverse predator assemblage.

    Science.gov (United States)

    Takizawa, Tadashi; Snyder, William E

    2011-02-01

    Greater biodiversity among aphid predators sometimes leads to greater predator reproductive success. This could occur if cannibalism of predator eggs is consistently stronger than intraguild predation, such that diversity dilutes cannibalism risk when total predator densities remain constant across diversity levels. We compared the frequency of cannibalism versus intraguild predation by adult predators of four species [the lady beetles Coccinella septempunctata L. and Hippodamia convergens Guerin-Meneville, and the predatory bugs Geocoris bullatus (Say) and Nabis alternatus Parshley] on the eggs of three predator species (all of these predators but Nabis). For both coccinellid species, egg predation averaged across all intraguild predators was less frequent than cannibalism. In contrast, Geocoris eggs were generally more likely to be consumed by intraguild predators than by conspecifics. Closer inspection of the data revealed that Geocoris consistently consumed fewer eggs than the other species, regardless of egg species. Indeed, for lady beetle eggs it was relatively infrequent egg predation by Geocoris that brought down the average across all heterospecific predators, masking the fact that adults of the two lady beetles were no more likely to act as egg cannibals than as intraguild predators. Nabis ate eggs of the two beetles at approximately equal rates, but rarely ate Geocoris eggs. Female predators generally consumed more eggs than did males, but this did not alter any of the patterns described above. Altogether, our results suggest that species-specific differences in egg predation rates determined the relative intensity of egg intraguild-predation versus cannibalism, rather than any more general trend for egg cannibalism to always exceed intraguild predation. © 2011 Entomological Society of America

  12. Landscape heterogeneity shapes predation in a newly restored predator-prey system.

    Science.gov (United States)

    Kauffman, Matthew J; Varley, Nathan; Smith, Douglas W; Stahler, Daniel R; MacNulty, Daniel R; Boyce, Mark S

    2007-08-01

    Because some native ungulates have lived without top predators for generations, it has been uncertain whether runaway predation would occur when predators are newly restored to these systems. We show that landscape features and vegetation, which influence predator detection and capture of prey, shape large-scale patterns of predation in a newly restored predator-prey system. We analysed the spatial distribution of wolf (Canis lupus) predation on elk (Cervus elaphus) on the Northern Range of Yellowstone National Park over 10 consecutive winters. The influence of wolf distribution on kill sites diminished over the course of this study, a result that was likely caused by territorial constraints on wolf distribution. In contrast, landscape factors strongly influenced kill sites, creating distinct hunting grounds and prey refugia. Elk in this newly restored predator-prey system should be able to mediate their risk of predation by movement and habitat selection across a heterogeneous risk landscape.

  13. Optimal control of native predators

    Science.gov (United States)

    Martin, Julien; O'Connell, Allan F.; Kendall, William L.; Runge, Michael C.; Simons, Theodore R.; Waldstein, Arielle H.; Schulte, Shiloh A.; Converse, Sarah J.; Smith, Graham W.; Pinion, Timothy; Rikard, Michael; Zipkin, Elise F.

    2010-01-01

    We apply decision theory in a structured decision-making framework to evaluate how control of raccoons (Procyon lotor), a native predator, can promote the conservation of a declining population of American Oystercatchers (Haematopus palliatus) on the Outer Banks of North Carolina. Our management objective was to maintain Oystercatcher productivity above a level deemed necessary for population recovery while minimizing raccoon removal. We evaluated several scenarios including no raccoon removal, and applied an adaptive optimization algorithm to account for parameter uncertainty. We show how adaptive optimization can be used to account for uncertainties about how raccoon control may affect Oystercatcher productivity. Adaptive management can reduce this type of uncertainty and is particularly well suited for addressing controversial management issues such as native predator control. The case study also offers several insights that may be relevant to the optimal control of other native predators. First, we found that stage-specific removal policies (e.g., yearling versus adult raccoon removals) were most efficient if the reproductive values among stage classes were very different. Second, we found that the optimal control of raccoons would result in higher Oystercatcher productivity than the minimum levels recommended for this species. Third, we found that removing more raccoons initially minimized the total number of removals necessary to meet long term management objectives. Finally, if for logistical reasons managers cannot sustain a removal program by removing a minimum number of raccoons annually, managers may run the risk of creating an ecological trap for Oystercatchers.

  14. Click here to start

    Indian Academy of Sciences (India)

    Click here to start. Table of contents. Slide 1 · Slide 2 · Slide 3 · Slide 4 · Slide 5 · Slide 6 · Slide 7 · Slide 8 · Slide 9 · Slide 10 · Slide 11 · Slide 12 · Slide 13 · Slide 14 · Slide 15 · Slide 16 · Slide 17 · Slide 18 · Slide 19 · Slide 20.

  15. Getting started with Hazelcast

    CERN Document Server

    Johns, Mat

    2013-01-01

    Written as a step-by-step guide, Getting Started with Hazelcast will teach you all you need to know to make your application data scalable.This book is a great introduction for Java developers, software architects, or developers looking to enable scalable and agile data within their applications. You should have programming knowledge of Java and a general familiarity with concepts like data caching and clustering.

  16. Instant Start Thyratron Switch.

    Science.gov (United States)

    1981-01-01

    COVEHRID Intnt Start Thyratron SicInterim 1st & 2nd Triannual R pt Swich *1 September 1979 - 1 May 1980 6. PERFORMING ORG. REPORT NUMBER 7. AUTHOR( S OTAC...White Oak Laboratory Electronic Warfare Lab, ERADCOM ATTN: Library, Code WX-21 White Sand Missile Range, Silver Spring, MD 20910 NM 88002 010 Defense...Documentation Center 001 Defense Communications Agency ATTN: DDC-TCA Technical Library Center Cameron Station (Bldg 5) Code 205 (P.A. Tolovi) Alexandria

  17. Getting started with JUCE

    CERN Document Server

    Robinson, Martin

    2013-01-01

    his book is a fast-paced, practical guide full of step-by-step examples which are easy to follow and implement.This book is for programmers with a basic grasp of C++. The examples start at a basic level, making few assumptions beyond fundamental C++ concepts. Those without any experience with C++ should be able to follow and construct the examples, although you may need further support to understand the fundamental concepts.

  18. Getting started with Simulink

    CERN Document Server

    Zamboni, Luca

    2013-01-01

    This practical and easy-to-understand learning tutorial is one big exciting exercise for students and engineers that are always short on their schedules and want to regain some lost time with the help of Simulink.This book is aimed at students and engineers who need a quick start with Simulink. Though it's not required in order to understand how Simulink works, knowledge of physics will help the reader to understand the exercises described.

  19. Improving the assessment of predator functional responses by considering alternate prey and predator interactions.

    Science.gov (United States)

    Chan, K; Boutin, S; Hossie, T J; Krebs, C J; O'Donoghue, M; Murray, D L

    2017-07-01

    To improve understanding of the complex and variable patterns of predator foraging behavior in natural systems, it is critical to determine how density-dependent predation and predator hunting success are mediated by alternate prey or predator interference. Despite considerable theory and debate seeking to place predator-prey interactions in a more realistic context, few empirical studies have quantified the role of alternate prey or intraspecific interactions on predator-prey dynamics. We assessed functional responses of two similarly sized, sympatric carnivores, lynx (Lynx canadensis) and coyotes (Canis latrans), foraging on common primary (snowshoe hares; Lepus americanus) and alternate (red squirrels; Tamiasciurus hudsonicus) prey in a natural system. Lynx exhibited a hyperbolic prey-dependent response to changes in hare density, which is characteristic of predators relying primarily on a single prey species. In contrast, the lynx-squirrel response was found to be linear ratio dependent, or inversely dependent on hare density. The coyote-hare and coyote-squirrel interactions also were linear and influenced by predator density. We explain these novel results by apparent use of spatial and temporal refuges by prey, and the likelihood that predators commonly experience interference and lack of satiation when foraging. Our study provides empirical support from a natural predator-prey system that (1) predation rate may not be limited at high prey densities when prey are small or rarely captured; (2) interference competition may influence the predator functional response; and (3) predator interference has a variable role across different prey types. Ultimately, distinct functional responses of predators to different prey types illustrates the complexity associated with predator-prey interactions in natural systems and highlights the need to investigate predator behavior and predation rate in relation to the broader ecological community. © 2017 by the Ecological

  20. Nature of Predation Risk Cues in Container Systems: Mosquito Responses to Solid Residues From Predation

    Science.gov (United States)

    KESAVARAJU, BANUGOPAN; JULIANO, STEVEN A.

    2012-01-01

    In aquatic systems, prey animals associate predation risk with cues that originate either from the predator or from injured conspecifics. Sources and benefits of these cues have received considerable attention in river, lake, and pond ecosystems but are less well understood in small container ecosystems that can hold less than a liter of water. Mosquitoes Aedes triseriatus (Say) and Aedes albopictus (Skuse) encounter predatory Corethrella appendiculata (Grabham) and Toxorhynchites rutilus (Coquillett) in small containers and show antipredatory behavioral responses. We investigated the sources of the predation cues to which these prey larvae respond. We tested whether Ae. albopictus larvae show behavioral responses to cues emanating from the predator or from damage to prey caused by the act of predation. We also tested whether Ae. triseriatus respond to cues present in fluid or solid residues from predator activity. Ae. albopictus showed behavioral modifications only in response to waterborne cues from a feeding predator and not to cues from a starving predator, indicating that Ae. albopictus respond to cues created by the act of predation, which could include substances derived from damaged prey or substances in predator feces. Ae. triseriatus showed behavioral responses to solid residues from predation but not to fluid without those solids, indicating that the cues to which they respond originate in predator feces or uneaten prey body parts. Our results suggest that cues in this system may be primarily chemicals that are detected upon contact with solid residues that are products of the feeding processes of these predators. PMID:22740721

  1. Getting started with Arduino

    CERN Document Server

    Banzi, Massimo

    2011-01-01

    Arduino is the open-source electronics prototyping platform that's taken the design and hobbyist world by storm. This thorough introduction, updated for Arduino 1.0, gives you lots of ideas for projects and helps you work with them right away. From getting organized to putting the final touches on your prototype, all the information you need is here! Inside, you'll learn about: Interaction design and physical computingThe Arduino hardware and software development environmentBasics of electricity and electronicsPrototyping on a solderless breadboardDrawing a schematic diagram Getting started

  2. Getting Started with Processing

    CERN Document Server

    Reas, Casey

    2010-01-01

    Learn computer programming the easy way with Processing, a simple language that lets you use code to create drawings, animation, and interactive graphics. Programming courses usually start with theory, but this book lets you jump right into creative and fun projects. It's ideal for anyone who wants to learn basic programming, and serves as a simple introduction to graphics for people with some programming skills. Written by the founders of Processing, this book takes you through the learning process one step at a time to help you grasp core programming concepts. You'll learn how to sketch wi

  3. Getting Started with Roo

    CERN Document Server

    Long, Josh

    2011-01-01

    Spring Roo goes a step beyond the Spring Framework by bringing true Rapid Application Development to Java-just as Grails has done with Groovy. This concise introduction shows you how to build applications with Roo, using the framework's shell as an intelligent and timesaving code-completion tool. It's an ideal RAD tool because Roo does much of the tedious code maintenance. You'll get started by building a simple customer relationship management application, complete with step-by-step instructions and code examples. Learn how to control any part of the application with Roo's opt-in feature, w

  4. En god start

    DEFF Research Database (Denmark)

    Sievertsen, Hans Henrik

    I Danmark er det muligt at afvige fra reglen om, at barnet skal starte i skole det kalenderår, hvor barnet fylder 6 år. Det gør 10-15 procent af en årgang, mens 80-90 procent af børnene følger normen, og 2-3 procent starter i skole et år tidligere end normen, viser en analyse baseret på børn født i...

  5. Getting Started with Netduino

    CERN Document Server

    Walker, Chris

    2012-01-01

    Start building electronics projects with Netduino, the popular open source hardware platform that's captured the imagination of makers and hobbyists worldwide. This easy-to-follow book provides the step-by-step guidance you need to experiment with Netduino and the .NET Micro Framework. Through a set of simple projects, you'll learn how to create electronic gadgets-including networked devices that communicate over TCP/IP. Along the way, hobbyists will pick up the basics of .NET programming, and programmers will discover how to work with electronics and microcontrollers. Follow the projects in

  6. Should the Lion Eat Straw Like the Ox? Animal Ethics and the Predation Problem

    NARCIS (Netherlands)

    Keulartz, Jozef

    2016-01-01

    Stephen Clark’s article The Rights of Wild Things from 1979 was the starting point for the consideration in the animal ethics literature of the so-called ‘predation problem’. Clark examines the response of David George Ritchie to Henry Stephens Salt, the first writer who has argued explicitly in

  7. Invasive predators and global biodiversity loss

    OpenAIRE

    Doherty, Tim S.; Glen, Alistair S.; Nimmo, Dale G.; Ritchie, Euan G.; Dickman, Chris R.

    2016-01-01

    Invasive mammalian predators are arguably the most damaging group of alien animal species for global biodiversity. Thirty species of invasive predator are implicated in the extinction or endangerment of 738 vertebrate species?collectively contributing to 58% of all bird, mammal, and reptile extinctions. Cats, rodents, dogs, and pigs have the most pervasive impacts, and endemic island faunas are most vulnerable to invasive predators. That most impacted species are insular indicates that manage...

  8. Intraguild relationships between sympatric predators exposed to lethal control: predator manipulation experiments

    National Research Council Canada - National Science Library

    Allen, Benjamin L; Allen, Lee R; Engeman, Richard M; Leung, Luke K-P

    2013-01-01

    .... The lethal control of top-predators has therefore been predicted to inhibit top-predator function, generate the release of mesopredators and indirectly harm native fauna through trophic cascade effects...

  9. The deadly effects of "nonlethal" predators.

    Science.gov (United States)

    McCauley, Shannon J; Rowe, Locke; Fortin, Marie-Josée

    2011-11-01

    Nonconsumptive predator effects are widespread and include plasticity as well as general stress responses. Caged predators are often used to estimate nonconsumptive effects, and numerous studies have focused on the larval stages of animals with complex life cycles. However, few of these studies test whether nonconsumptive predator effects, including stress responses, are exclusively sublethal. Nor have they assessed whether these effects extend beyond the larval stage, affecting success during stressful life-history transitions such as metamorphosis. We conducted experiments with larvae of a dragonfly (Leucorrhinia intacta) that exhibits predator-induced plasticity to assess whether the mere presence of predators affects larval survivorship, metamorphosis, and adult body size. Larvae exposed to caged predators with no ability to attack them had higher levels of mortality. In the second experiment, larvae reared with caged predators had higher rates of metamorphic failure, but there was no effect on adult body size. Our results suggest that stress responses induced by exposure to predator cues increase the vulnerability of prey to other mortality factors, and that mere exposure to predators can result in significant increases in mortality.

  10. Use of Plant Resources by an Omnivorous Predator and the Consequences for Effective Predation

    NARCIS (Netherlands)

    Maselou, D.A.; Perdikis, D. Ch.; Sabelis, M.W.; Fantinou, A.A.

    2014-01-01

    Plant-provided food may enhance survival and establishment of omnivorous predators on target crops but on the other hand they may adversely affect predation rates and thus their potential for biological control of target pests. However, it is not known how predation is affected by plant food quality

  11. Predator effects on reef fish settlement depend on predator origin and recruit density.

    Science.gov (United States)

    Benkwitt, Cassandra E

    2017-04-01

    During major life-history transitions, animals often experience high mortality rates due to predation, making predator avoidance particularly advantageous during these times. There is mixed evidence from a limited number of studies, however, regarding how predator presence influences settlement of coral-reef fishes and it is unknown how other potentially mediating factors, including predator origin (native vs. nonnative) or interactions among conspecific recruits, mediate the non-consumptive effects of predators on reef fish settlement. During a field experiment in the Caribbean, approximately 52% fewer mahogany snapper (Lutjanus mahogoni) recruited to reefs with a native predator (graysby grouper, Cephalopholis cruentata) than to predator-free control reefs and reefs with an invasive predator (red lionfish, Pterois volitans) regardless of predator diet. These results suggest that snapper recruits do not recognize nonnative lionfish as a threat. However, these effects depended on the density of conspecific recruits, with evidence that competition may limit the response of snapper to even native predators at the highest recruit densities. In contrast, there was no effect of predator presence or conspecific density on the recruitment of bicolor damselfish (Stegastes partitus). These context-dependent responses of coral-reef fishes to predators during settlement may influence individual survival and shape subsequent population and community dynamics. © 2017 by the Ecological Society of America.

  12. Wanted dead or alive: scavenging versus predation by three insect predators

    Science.gov (United States)

    Many generalist insect predators may engage in facultative scavenging. If an apparent predator frequently consumes dead prey instead of live prey then the biological control services provided by that predator may be overestimated. The use of unique protein markers on live and dead prey of the same s...

  13. Intraguild interactions among three spider mite predators: predation preference and effects on juvenile development and oviposition.

    Science.gov (United States)

    Rahmani, Hasan; Daneshmandi, Aliakbar; Walzer, Andreas

    2015-12-01

    A first step to evaluate potential negative effects of intraguild predation (IGP) when using multiple predators against a pest species is the determination of the predation behavior of the predators and the nutritional value of intraguild (IG) prey in terms of development and oviposition. Here, we investigated the predation preference of the female predatory mites Neoseiulus californicus, Typhlodromus bagdasarjani and Phytoseius plumifer, when having choice between larvae of the two other predatory mite species (IG prey) with and without extraguild prey, the spider mite Tetranychus urticae (EG prey). Additionally, we evaluated the juvenile development and oviposition of the three predator species when provided with larvae from each other species. Irrespective of EG prey, IG prey species affected neither the first attack nor attack times of the three female IG predator species. The IG predation rates of the predator females, however, were influenced by prey species in the absence of EG prey. Neoseiulus californicus females killed more P. plumifer than T. bagdasarjani larvae, whereas T. bagdasarjani and P. plumifer females killed more N. californicus than P. plumifer and T. bagdasarjani larvae, respectively. All IG predator species consumed significantly more EG than IG prey. IG prey species did not influence juvenile and adult survival probabilities of the IG predators. We conclude that IGP is a weak force among the three predators and the potential consequences of IGP should not result in the elimination of one by another tested predatory mite species at least in the presence of spider mites.

  14. Invasive rats strengthen predation pressure on bird eggs in a South Pacific island rainforest.

    Science.gov (United States)

    Duron, Quiterie; Bourguet, Edouard; De Meringo, Hélène; Millon, Alexandre; Vidal, Eric

    2017-12-01

    Invasive rats ( Rattus spp.) are known to have pervasive impacts on island birds, particularly on their nesting success. To conserve or restore bird populations, numerous invasive rat control or eradication projects are undertaken on islands worldwide. However, such projects represent a huge investment and the decision-making process requires proper assessment of rat impacts. Here, we assessed the influence of two sympatric invasive rats ( Rattus rattus and R. exulans ) on native bird eggs in a New Caledonian rainforest, using artificial bird-nest monitoring. A total of 178 artificial nests containing two eggs of three different sizes were placed either on the ground or 1.5 m high and monitored at the start of the birds' breeding season. Overall, 12.4% of the nests were depredated during the first 7 days. At site 1, where nests were monitored during 16 days, 41.8% of the nests were depredated. The main predator was the native crow Corvus moneduloides , responsible for 62.9% of the overall predation events. Rats were responsible for only 22.9% of the events, and ate only small and medium eggs at both heights. Our experiment suggests that in New Caledonia, predation pressure by rats strengthens overall bird-nest predation, adding to that by native predators. Experimental rat control operations may allow reduced predation pressure on nests as well as the recording of biodiversity responses after rat population reduction.

  15. The Healthy Start project

    DEFF Research Database (Denmark)

    Olsen, Nanna J; Buch-Andersen, Tine; Händel, Mina N

    2012-01-01

    , and to intervene not only by improving diet and physical activity, but also reduce stress and improve sleep quality and quantity. METHODS: Based on information from the Danish national birth registry and administrative birth forms, children were selected based on having either high birth weight, a mother who......-going, but it is estimated that 394 children will be included. The intervention took place over on average 11/2 year, between 2009 and 2011, and consisted of optional individual guidance in optimizing diet and physical activity habits, reducing chronic stress and stressful events and improving sleep quality and quantity....... The intervention also included participation in cooking classes and play arrangements. Information on dietary intake, meal habits, physical activity, sleep habits, and overall stress level was obtained by 4-7 day questionnaire dairies and objective measurements. DISCUSSION: If the Healthy Start project...

  16. Nest Predation Deviates from Nest Predator Abundance in an Ecologically Trapped Bird.

    Science.gov (United States)

    Hollander, Franck A; Van Dyck, Hans; San Martin, Gilles; Titeux, Nicolas

    2015-01-01

    In human-modified environments, ecological traps may result from a preference for low-quality habitat where survival or reproductive success is lower than in high-quality habitat. It has often been shown that low reproductive success for birds in preferred habitat types was due to higher nest predator abundance. However, between-habitat differences in nest predation may only weakly correlate with differences in nest predator abundance. An ecological trap is at work in a farmland bird (Lanius collurio) that recently expanded its breeding habitat into open areas in plantation forests. This passerine bird shows a strong preference for forest habitat, but it has a higher nest success in farmland. We tested whether higher abundance of nest predators in the preferred habitat or, alternatively, a decoupling of nest predator abundance and nest predation explained this observed pattern of maladaptive habitat selection. More than 90% of brood failures were attributed to nest predation. Nest predator abundance was more than 50% higher in farmland, but nest predation was 17% higher in forest. Differences between nest predation on actual shrike nests and on artificial nests suggested that parent shrikes may facilitate nest disclosure for predators in forest more than they do in farmland. The level of caution by parent shrikes when visiting their nest during a simulated nest predator intrusion was the same in the two habitats, but nest concealment was considerably lower in forest, which contributes to explaining the higher nest predation in this habitat. We conclude that a decoupling of nest predator abundance and nest predation may create ecological traps in human-modified environments.

  17. Nest Predation Deviates from Nest Predator Abundance in an Ecologically Trapped Bird.

    Directory of Open Access Journals (Sweden)

    Franck A Hollander

    Full Text Available In human-modified environments, ecological traps may result from a preference for low-quality habitat where survival or reproductive success is lower than in high-quality habitat. It has often been shown that low reproductive success for birds in preferred habitat types was due to higher nest predator abundance. However, between-habitat differences in nest predation may only weakly correlate with differences in nest predator abundance. An ecological trap is at work in a farmland bird (Lanius collurio that recently expanded its breeding habitat into open areas in plantation forests. This passerine bird shows a strong preference for forest habitat, but it has a higher nest success in farmland. We tested whether higher abundance of nest predators in the preferred habitat or, alternatively, a decoupling of nest predator abundance and nest predation explained this observed pattern of maladaptive habitat selection. More than 90% of brood failures were attributed to nest predation. Nest predator abundance was more than 50% higher in farmland, but nest predation was 17% higher in forest. Differences between nest predation on actual shrike nests and on artificial nests suggested that parent shrikes may facilitate nest disclosure for predators in forest more than they do in farmland. The level of caution by parent shrikes when visiting their nest during a simulated nest predator intrusion was the same in the two habitats, but nest concealment was considerably lower in forest, which contributes to explaining the higher nest predation in this habitat. We conclude that a decoupling of nest predator abundance and nest predation may create ecological traps in human-modified environments.

  18. Does sex-selective predation stabilize or destabilize predator-prey dynamics?

    Directory of Open Access Journals (Sweden)

    David S Boukal

    Full Text Available BACKGROUND: Little is known about the impact of prey sexual dimorphism on predator-prey dynamics and the impact of sex-selective harvesting and trophy hunting on long-term stability of exploited populations. METHODOLOGY AND PRINCIPAL FINDINGS: We review the quantitative evidence for sex-selective predation and study its long-term consequences using several simple predator-prey models. These models can be also interpreted in terms of feedback between harvesting effort and population size of the harvested species under open-access exploitation. Among the 81 predator-prey pairs found in the literature, male bias in predation is 2.3 times as common as female bias. We show that long-term effects of sex-selective predation depend on the interplay of predation bias and prey mating system. Predation on the 'less limiting' prey sex can yield a stable predator-prey equilibrium, while predation on the other sex usually destabilizes the dynamics and promotes population collapses. For prey mating systems that we consider, males are less limiting except for polyandry and polyandrogyny, and male-biased predation alone on such prey can stabilize otherwise unstable dynamics. On the contrary, our results suggest that female-biased predation on polygynous, polygynandrous or monogamous prey requires other stabilizing mechanisms to persist. CONCLUSIONS AND SIGNIFICANCE: Our modelling results suggest that the observed skew towards male-biased predation might reflect, in addition to sexual selection, the evolutionary history of predator-prey interactions. More focus on these phenomena can yield additional and interesting insights as to which mechanisms maintain the persistence of predator-prey pairs over ecological and evolutionary timescales. Our results can also have implications for long-term sustainability of harvesting and trophy hunting of sexually dimorphic species.

  19. Predator-driven intra-species variation in locomotion, metabolism and water velocity preference in pale chub (Zacco platypus) along a river.

    Science.gov (United States)

    Fu, Cheng; Fu, Shi-Jian; Yuan, Xin-Zhong; Cao, Zhen-Dong

    2015-01-15

    Fish inhabit environments that vary greatly in terms of predation intensity, and these predation regimes are generally expected to be a major driver of divergent natural selection. To test whether there is predator-driven intra-species variation in the locomotion, metabolism and water velocity preference of pale chub (Zacco platypus) along a river, we measured unsteady and steady swimming and water velocity preference among fish collected from both high- and low-predation habitats in the Wujiang River. We also measured the routine metabolic rate (RMR), maximum metabolic rate (MMR) and cost of transport (COT) and calculated the optimal swimming speed (Uopt). The fish from the high-predation populations showed a shorter response latency, elevated routine metabolism, lower swimming efficiency at low swimming speed and lower water velocity preference compared with those from the low-predation populations. Neither of the kinematic parameters fast-start and critical swimming speed (Ucrit) showed a significant difference between the high- and low-predation populations. The fish from the high-predation populations may improve their predator avoidance capacity primarily through an elevated routine metabolism and shorter response latency to achieve advanced warning and escape, rather than an improved fast-start swimming speed or acceleration. Thus, the cost of this strategy is an elevated RMR, and no trade-off between unsteady and steady swimming performance was observed in the pale chub population under various predation stresses. It was interesting to find that the high-predation fish showed an unexpected lower velocity preference, which might represent a compromise between predation avoidance, foraging and energy saving. © 2015. Published by The Company of Biologists Ltd.

  20. Modeling predator habitat to enhance reintroduction planning

    Science.gov (United States)

    Shiloh M. Halsey; William J. Zielinski; Robert M. Scheller

    2015-01-01

    Context The success of species reintroduction often depends on predation risk and spatial estimates of predator habitat. The fisher (Pekania pennanti) is a species of conservation concern and populations in the western United States have declined substantially in the last century. Reintroduction plans are underway, but the ability...

  1. The functional response of a generalist predator.

    Directory of Open Access Journals (Sweden)

    Sophie Smout

    Full Text Available BACKGROUND: Predators can have profound impacts on the dynamics of their prey that depend on how predator consumption is affected by prey density (the predator's functional response. Consumption by a generalist predator is expected to depend on the densities of all its major prey species (its multispecies functional response, or MSFR, but most studies of generalists have focussed on their functional response to only one prey species. METHODOLOGY AND PRINCIPAL FINDINGS: Using Bayesian methods, we fit an MSFR to field data from an avian predator (the hen harrier Circus cyaneus feeding on three different prey species. We use a simple graphical approach to show that ignoring the effects of alternative prey can give a misleading impression of the predator's effect on the prey of interest. For example, in our system, a "predator pit" for one prey species only occurs when the availability of other prey species is low. CONCLUSIONS AND SIGNIFICANCE: The Bayesian approach is effective in fitting the MSFR model to field data. It allows flexibility in modelling over-dispersion, incorporates additional biological information into the parameter priors, and generates estimates of uncertainty in the model's predictions. These features of robustness and data efficiency make our approach ideal for the study of long-lived predators, for which data may be sparse and management/conservation priorities pressing.

  2. LEP dismantling starts

    CERN Multimedia

    2000-01-01

    Since the end of November, various teams have been getting stuck into dismantling the LEP accelerator and its four experiments. After making the installations safe, the dismantling and removal of 40,000 tonnes of equipment is underway. Down in the tunnel, it is a solemn moment. It is 10 o'clock on 13 December and Daniel Regin, one of those heading the dismantling work, moves in on a magnet, armed with a hydraulic machine. Surrounded by teams gathered there for a course in dismantling, he makes the first cut into LEP. The great deconstruction has begun. In little over than a year, the accelerator will have been cleared away to make room for its successor, the LHC. The start of the operation goes back to 27 November. Because before setting about the machine with hydraulic shears and monkey wrenches, LEP had first to be made safe - it was important to make sure the machine could be taken apart without risk. All the SPS beam injection systems to LEP were cut off. The fluids used for cooling the magnets and superc...

  3. Starting physiology: bioelectrogenesis.

    Science.gov (United States)

    Baptista, Vander

    2015-12-01

    From a Cartesian perspective of rational analysis, the electric potential difference across the cell membrane is one of the fundamental concepts for the study of physiology. Unfortunately, undergraduate students often struggle to understand the genesis of this energy gradient, which makes the teaching activity a hard task for the instructor. The topic of bioelectrogenesis encompasses multidisciplinary concepts, involves several mechanisms, and is a dynamic process, i.e., it never turns off during the lifetime of the cell. Therefore, to improve the transmission and acquisition of knowledge in this field, I present an alternative didactic model. The design of the model assumes that it is possible to build, in a series of sequential steps, an assembly of proteins within the membrane of an isolated cell in a simulated electrophysiology experiment. Initially, no proteins are inserted in the membrane and the cell is at a baseline energy state; the extracellular and intracellular fluids are at thermodynamic equilibrium. Students are guided through a sequence of four steps that add key membrane transport proteins to the model cell. The model is simple at the start and becomes progressively more complex, finally producing transmembrane chemical and electrical gradients. I believe that this didactic approach helps instructors with a more efficient tool for the teaching of the mechanisms of resting membrane potential while helping students avoid common difficulties that may be encountered when learning this topic. Copyright © 2015 The American Physiological Society.

  4. An impressive start

    CERN Multimedia

    2011-01-01

    This has been an excellent week for the LHC, with a succession of fills rapidly increasing the number of proton bunches to 194 per beam. This has allowed the experiments to reach a peak luminosity of 2.5 × 1032 cm-2s-1, thereby surpassing the record for 2010 where we reached 2.0 × 1032 cm-2s-1. At the time of writing, the integrated luminosity delivered by the LHC in 2011 is around 28 inverse picobarns, which is already more than half of the total 2010 dataset.   These are impressive numbers, but what impresses me most is how quickly the LHC operators are now able to turn the machine around between fills, and how well LHC running has been incorporated into the overall operation of CERN’s accelerator complex. The flexibility of the LHC was illustrated on Thursday when we started a short phase of running at 1.38 TeV per beam, equivalent to the energy-per-nucleon of a lead-ion run. This lower energy data will be used by the experiments, in particular by ALICE, to compare...

  5. ATLAS starts moving in

    CERN Multimedia

    Della Mussia, S

    2004-01-01

    The first large active detector component was lowered into the ATLAS cavern on 1st March. It consisted of the 8 modules forming the lower part of the central barrel of the tile hadronic calorimeter. The work of assembling the barrel, which comprises 64 modules, started the following day. Two road trailers each with 64 wheels, positioned side by side. This was the solution chosen to transport the lower part of the central barrel of ATLAS' tile hadronic calorimeter from Building 185 to the PX16 shaft at Point 1 (see Figure 1). The transportation, and then the installation of the component in the experimental cavern, which took place over three days were, to say the least, rather spectacular. On 25 February, the component, consisting of eight 6-metre modules, was loaded on to the trailers. The segment of the barrel was transported on a steel support so that it wouldn't move an inch during the journey. On 26 February, once all the necessary safety checks had been carried out, the convoy was able to leave Buildi...

  6. Predation on dormice in Italy

    Directory of Open Access Journals (Sweden)

    Dino Scaravelli

    1995-05-01

    Full Text Available Abstract The authors analyse available data on the impact of predators on Dormouse populations in Italy. Dormice are found in the diet of 2 snakes (Vipera berus and V. aspis, 2 diurnal birds of prey (Buteo buteo and Aquila chrysaetos, 6 owls (Tyto alba, Strix aluco, Asio otus, Athene noctua, Bubo bubo and Glaucidium passerinum and 9 mammals (Rattus rattus, Ursus arctos, Canis lupus, Vulpes vulpes, Martes martes, M. foina, Meles meles, Felis silvestris and Sus scrofa in a variable percentage of the prey taken. Only Dryomys nitedula was never encountered as a prey item. The most common prey is Muscardinus avellanarius. There are significative regional differences in predation between bioclimatic areas of the Italian peninsula. The contribution of studies on predation to knowledge of Myoxid distribution is discussed. Riassunto Predazione di Mioxidi in Italia - Sono analizzati i dati pubblicati sull'impatto dei predatori sulle popolazioni di Myoxidae in Italia. Myoxidae sono stati riscontrati nelle diete di 2 serpenti (Vipera berus e V. aspis, 2 rapaci diurni (Buteo buteo e Aquila chrysaetos, 6 notturni (Tyto alba, Strix aluco, Asio otus, Athene noctua, Bubo bubo e Glaucidium passerinum e 9 mammiferi (Rattus rattus, Ursus arctos, Canis lupus, Vulpes vulpes, Martes martes, M foina, Meles meles, Felis silvestris e Sus scrofa in percentuale variabile nella comunità di prede. Solo Dryomys nitedula non è mai stato incontrato come preda. La specie piu comunemente predata risulta Muscardinus avellanarius. Sono discusse le

  7. Drosophila increase exploration after visually detecting predators.

    Directory of Open Access Journals (Sweden)

    Miguel de la Flor

    Full Text Available Novel stimuli elicit behaviors that are collectively known as specific exploration. These behaviors allow the animal to become more familiar with the novel objects within its environment. Specific exploration is frequently suppressed by defensive reactions to predator cues. Herein, we examine if this suppression occurs in Drosophila melanogaster by measuring the response of these flies to wild harvested predators. The flies used in our experiments have been cultured and had not lived under predator threat for multiple decades. In a circular arena with centrally-caged predators, wild type Drosophila actively avoided the pantropical jumping spider, Plexippus paykulli, and the Texas unicorn mantis, Phyllovates chlorophaena, indicating an innate defensive reaction to these predators. Interestingly, wild type Drosophila males also avoided a centrally-caged mock spider, and the avoidance of the mock spider became exaggerated when it was made to move within the cage. Visually impaired Drosophila failed to detect and avoid the Plexippus paykulli and the moving mock spider, while the broadly anosmic orco2 mutants were fully capable of detecting and avoiding Plexippus paykulli, indicating that these flies principally relied upon vison to perceive the predator stimuli. During early exploration of the arena, exploratory activity increased in the presence of Plexippus paykulli and the moving mock spider. The elevated activity induced by Plexippus paykulli disappeared after the fly had finished exploring, suggesting the flies were capable of habituating the predator cues. Taken together, these results indicate that despite being isolated from predators for decades Drosophila will visually detect these predators, retain innate defensive behaviors, respond by increasing exploratory activity in the arena rather than suppressing activity, and may habituate to normal predator cues.

  8. The behavioral response of prey fish to predators: the role of predator size

    Directory of Open Access Journals (Sweden)

    Zhong-Hua Tang

    2017-04-01

    Full Text Available Predation is one of the key factors governing patterns in natural systems, and adjustments of prey behaviors in response to a predator stimulus can have important ecological implications for wild fish. To investigate the effects of predators on the behavior of prey fish and to test whether the possible effects varied with predator size, black carp (Mylopharyngodon piceus and snakehead (Channa argus (a size-matched predator treatment with a similar body size to prey fish and a larger predator treatment with approximately 2.7 times of the body mass of prey fish were selected to function as prey and predator, respectively. Their spontaneous activities were videorecorded in a central circular arena surrounded by a ring holding the stimulus fish. The distance between prey and predator fish was approximately 200% of the distance between two prey fish, which suggested that black carp can distinguish their conspecifics from heterospecifics and probably recognize the snakehead as a potential predator. The prey fish spent substantially less time moving and exhibited an overall shorter total distance of movement after the size-matched or large predator was introduced, which possibly occurred due to increased vigilance or efforts to reduce the possibility of detection by potential predators. However, there was no significant difference in either distance or spontaneous activities between two predator treatments. These findings suggested that (1 an anti-predator strategy in black carp might involve maintaining a safe distance, decreasing activity and possibly increased vigilance and that (2 the behaviors of prey response to predators were not influenced by their relative size difference.

  9. Predators are attracted to the olfactory signals of prey

    National Research Council Canada - National Science Library

    Hughes, Nelika K; Price, Catherine J; Banks, Peter B

    2010-01-01

    .... Yet while most territorial mammals communicate using olfactory signals and olfactory hunting is widespread in predators, evidence for the attraction of predators to prey olfactory signals under field...

  10. From Head Start to Sure Start: Reflections on Policy Transfer

    Science.gov (United States)

    Welshman, John

    2010-01-01

    This article uses the history of debates over the US Head Start programme (1965), Early Head Start (1994) and the UK Sure Start initiative (1998), as a window on to policy transfer. In all the three, the aim was that early intervention could offer a means of boosting children's educational attainment and of countering the wider effects of poverty…

  11. Predation on rose galls: parasitoids and predators determine gall size through directional selection.

    Directory of Open Access Journals (Sweden)

    Zoltán László

    Full Text Available Both predators and parasitoids can have significant effects on species' life history traits, such as longevity or clutch size. In the case of gall inducers, sporadically there is evidence to suggest that both vertebrate predation and insect parasitoid attack may shape the optimal gall size. While the effects of parasitoids have been studied in detail, the influence of vertebrate predation is less well-investigated. To better understand this aspect of gall size evolution, we studied vertebrate predation on galls of Diplolepis rosae on rose (Rosa canina shrubs. We measured predation frequency, predation incidence, and predation rate in a large-scale observational field study, as well as an experimental field study. Our combined results suggest that, similarly to parasitoids, vertebrate predation makes a considerable contribution to mortality of gall inducer larvae. On the other hand, its influence on gall size is in direct contrast to the effect of parasitoids, as frequency of vertebrate predation increases with gall size. This suggests that the balance between predation and parasitoid attack shapes the optimal size of D. rosae galls.

  12. The increased risk of predation enhances cooperation

    Science.gov (United States)

    Krams, Indrikis; Bērziņš, Arnis; Krama, Tatjana; Wheatcroft, David; Igaune, Kristīne; Rantala, Markus J.

    2010-01-01

    Theory predicts that animals in adverse conditions can decrease individual risks and increase long-term benefits by cooperating with neighbours. However, some empirical studies suggest that animals often focus on short-term benefits, which can reduce the likelihood that they will cooperate with others. In this experimental study, we tested between these two alternatives by evaluating whether increased predation risk (as a correlate of environmental adversity) enhances or diminishes the occurrence of cooperation in mobbing, a common anti-predator behaviour, among breeding pied flycatchers Ficedula hypoleuca. We tested whether birds would join their mobbing neighbours more often and harass a stuffed predator placed near their neighbours' nests more intensely in areas with a higher perceived risk of predation. Our results show that birds attended mobs initiated by their neighbours more often, approached the stuffed predator significantly more closely, and mobbed it at a higher intensity in areas where the perceived risk of predation was experimentally increased. In such high-risk areas, birds also were more often involved in between-pair cooperation. This study demonstrates the positive impact of predation risk on cooperation in breeding songbirds, which might help in explaining the emergence and evolution of cooperation. PMID:19846454

  13. School Starting Age and Crime

    DEFF Research Database (Denmark)

    Landersø, Rasmus; Nielsen, Helena Skyt; Simonsen, Marianne

    This paper investigates the effects of school starting age on crime while relying on variation in school starting age induced by administrative rules; we exploit that Danish children typically start first grade in the calendar year they turn seven, which gives rise to a discontinuity in children......’s school starting age. Analyses are carried out using register-based Danish data. We find that higher age at school start lowers the propensity to commit crime, but that this reduction is caused by incapacitation while human capital accumulation is unaffected. Importantly, we also find that the individuals...

  14. The mind of the sexual predator.

    Science.gov (United States)

    Palermo, George B

    2007-09-01

    This review reports recent articles in the criminological literature that may be of help in understanding the psychodynamics of sexual predators in the hope of better defining them and preventing recidivistic behavior. Recent literature presents the motivations behind sexual offending, attempting to explain in a psychodynamic way the complex problem of the aberrant sexual drives of the sexual predator. Recent civil commitment laws and their implications are touched upon. The literature presented will enable the criminology practitioner to reach a more holistic understanding of the sexual predator and better detection of them.

  15. Predation among armored arachnids: Bothriurus bonariensis (Scorpions, Bothriuridae) versus four species of harvestmen (Harvestmen, Gonyleptidae).

    Science.gov (United States)

    Albín, Andrea; Toscano-Gadea, Carlos A

    2015-12-01

    Natural selection shapes prey-predator relationships and their behavioral adaptations, which seek to maximize capture success in the predator and avoidance in the prey. We tested the ability of adults of the scorpion Bothriurus bonariensis (Bothriuridae) to prey on synchronous and sympatric adults harvestmen of Acanthopachylus aculeatus, Discocyrtus prospicuus, Parampheres bimaculatus and Pachyloides thorellii (Gonyleptidae). In 72.5% of the cases B. bonariensis tried to prey on the harvestmen. The most successful captures occurred in the trials against A. aculeatus and D. prospicuus. In all the successful attacks the scorpions stung the prey between the chelicerae and consumed them, starting by the anterior portion of their bodies. The harvestmen used different defensive strategies such as fleeing before or after contact with the predator, exudating of chemical substances or staying still at the scorpion's touch. When scorpions contacted the chemical substances secreted by the harvestmen, they immediately rubbed the affected appendix against the substrate. However, exudating of chemical substances did not prevent, in any case, predation on the harvestmen. This is the first study showing the ability of scorpions to prey on different species of harvestmen, as well as the capture and defensive behaviors used by the predator and the prey. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Generalist red velvet mite predator (Balaustium sp.) performs better on a mixed diet.

    Science.gov (United States)

    Muñoz-Cárdenas, Karen; Fuentes, Luz Stella; Cantor, R Fernando; Rodríguez, C Daniel; Janssen, Arne; Sabelis, Maurice W

    2014-01-01

    Generalist predators have the potential advantage to control more than one pest and to be more persistent than specialist predators because they can survive on different foods. Moreover, their population growth rate may be elevated when offered a mixture of prey species. We studied a generalist predatory mite Balaustium sp. that shows promise for biological control of thrips and whiteflies in protected rose cultures in Colombia. Although starting its life in the soil, this predator makes excursions onto plants where it feeds on various arthropods. We quantified life history parameters of the predator, offering high densities of three pest species: first-instar larvae of Frankliniella occidentalis, eggs of Trialeurodes vaporariorum and Tetranychus urticae, either alone or in combination. The predators completed their life cycle on each diet. The egg-to-egg period was c. 2 months. All eggs were laid in one batch in 1-2 days, indicating a pronounced semelparous reproduction pattern. In general, females reproduced earlier and laid more eggs on mixed diets, and these early reproducers consequently had higher population growth rates than late reproducers. The best diet in terms of egg-to-egg period and juvenile survival was the combination of eggs from whiteflies and spider mites. Spider mite eggs alone and western flower thrips larvae alone were the worst diets. It remains to be investigated whether mixed diets promote the population growth rate of Balaustium sufficiently for biocontrol of whiteflies and thrips in the presence of alternative prey, such as spider mites, to become effective.

  17. Nest Predation Deviates from Nest Predator Abundance in an Ecologically Trapped Bird

    OpenAIRE

    Hollander, Franck A.; Van Dyck, Hans; San Martin, Gilles; Titeux, Nicolas

    2015-01-01

    In human-modified environments, ecological traps may result from a preference for low-quality habitat where survival or reproductive success is lower than in high-quality habitat. It has often been shown that low reproductive success for birds in preferred habitat types was due to higher nest predator abundance. However, between-habitat differences in nest predation may only weakly correlate with differences in nest predator abundance. An ecological trap is at work in a farmland bird (Lanius ...

  18. A predator-prey system with stage-structure for predator and nonlocal delay

    DEFF Research Database (Denmark)

    Lin, Z.G.; Pedersen, Michael; Zhang, Lai

    2010-01-01

    This paper deals with the behavior of solutions to the reaction-diffusion system under homogeneous Neumann boundary condition, which describes a prey-predator model with nonlocal delay. Sufficient conditions for the global stability of each equilibrium are derived by the Lyapunov functional and t...... and the results show that the introduction of stage-structure into predator positively affects the coexistence of prey and predator. Numerical simulations are performed to illustrate the results....

  19. The effect of fish predation on benthic macroinvertebrates in a ...

    African Journals Online (AJOL)

    Results indicate that, although fish may be important predators, they are not keystone predators because the macroinvertebrate community structure in this temporary habitat was found to be influenced by the assemblages of both vertebrate and invertebrate predators, rather than by a single keystone predator. Keywords: ...

  20. Predation risk of artificial ground nests in managed floodplain meadows

    Science.gov (United States)

    Arbeiter, Susanne; Franke, Elisabeth

    2018-01-01

    Nest predation highly determines the reproductive success in birds. In agricultural grasslands, vegetation characteristics and management practices influences the predation risk of ground breeders. Little is known so far on the predation pressure on non-passerine nests in tall swards. Investigations on the interaction of land use with nesting site conditions and the habitat selection of nest predators are crucial to develop effective conservation measures for grassland birds. In this study, we used artificial nests baited with quail and plasticine eggs to identify potential predators of ground nests in floodplain meadows and related predation risk to vegetation structure and grassland management. Mean daily predation rate was 0.01 (±0.012) after an exposure duration of 21 days. 70% of all observed nest predations were caused by mammals (Red Fox and mustelids) and 17.5% by avian predators (corvids). Nest sites close to the meadow edge and those providing low forb cover were faced with a higher daily predation risk. Predation risk also increased later in the season. Land use in the preceding year had a significant effect on predation risk, showing higher predation rates on unmanaged sites than on mown sites. Unused meadows probably attract mammalian predators, because they provide a high abundance of small rodents and a more favourable vegetation structure for foraging, increasing also the risk of incidental nest predations. Although mowing operation is a major threat to ground-nesting birds, our results suggest that an annual removal of vegetation may reduce predation risk in the subsequent year.

  1. Ants, rodents and seed predation in Proteaceae

    African Journals Online (AJOL)

    . Saasveld Forestry Research Centre, George. Many species of Cape Proteaceae have seeds dispersed by ants. Ants may reduce seed predation by rapidly transporting and burying seeds in their nests. Three field experiments using ant and ...

  2. Predator cognition permits imperfect coral snake mimicry.

    Science.gov (United States)

    Kikuchi, David W; Pfennig, David W

    2010-12-01

    Batesian mimicry is often imprecise. An underexplored explanation for imperfect mimicry is that predators might not be able to use all dimensions of prey phenotype to distinguish mimics from models and thus permit imperfect mimicry to persist. We conducted a field experiment to test whether or not predators can distinguish deadly coral snakes (Micrurus fulvius) from nonvenomous scarlet kingsnakes (Lampropeltis elapsoides). Although the two species closely resemble one another, the order of colored rings that encircle their bodies differs. Despite this imprecise mimicry, we found that L. elapsoides that match coral snakes in other respects are not under selection to match the ring order of their model. We suggest that L. elapsoides have evolved only those signals necessary to deceive predators. Generally, imperfect mimicry might suffice if it exploits limitations in predator cognitive abilities.

  3. Predation on Daphnia pulex by Lepidurus arcticus

    DEFF Research Database (Denmark)

    Christoffersen, Kirsten Seestern

    2001-01-01

    when swimming in the water. Experiments were set up to test how efficiently Lepidurus hunts Daphnia and if a functional response between predator and prey exists. It was also tested if temperature and Lepidurus size played a significant role for the predation rate. Lepidurus and Daphnia were sampled...... predation rates were biased due to the manipulated conditions (e.g. increased encounter rates), Lepidurus appears to be an active and efficient predator on planktonic prey, and its presence in arctic lakes and ponds may consequently have a significant impact on the structure of the planktonic food web....... The calculated energetic advantages of plankton as supplement to a benthic diet seemed low (5% of body weight per day)....

  4. Biodiversity effects of the predation gauntlet

    Science.gov (United States)

    Stier, Adrian C.; Stallings, Christopher D.; Samhouri, Jameal F.; Albins, Mark A.; Almany, Glenn R.

    2017-06-01

    The ubiquity of trophic downgrading has led to interest in the consequences of mesopredator release on prey communities and ecosystems. This issue is of particular concern for reef-fish communities, where predation is a key process driving ecological and evolutionary dynamics. Here, we synthesize existing experiments that have isolated the effects of mesopredators to quantify the role of predation in driving changes in the abundance and biodiversity of recently settled reef fishes. On average, predators reduced prey abundance through generalist foraging behavior, which, through a statistical sampling artifact, caused a reduction in alpha diversity and an increase in beta diversity. Thus, the synthesized experiments provide evidence that predation reduces overall abundance within prey communities, but—after accounting for sampling effects—does not cause disproportionate effects on biodiversity.

  5. Apex Predators Program Age and Growth Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Apex Predators Program staff have collected vertebral centra from sportfishing tournaments, cruises, commercial fishermen and strandings in the Northeast US since...

  6. Apex Predators Program Sportfishing Tournament Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Apex Predators Program staff have collected shark sportfishing tournamant data from the Northeast US since the 1960's. These tournaments offer a unique opportunity...

  7. Limited predator-induced dispersal in whiteflies.

    Directory of Open Access Journals (Sweden)

    Rui-Xia Meng

    Full Text Available Whereas prey are known to avoid habitats with their predators, it is less well established whether they are triggered to emigrate to new habitats when exposed to predators in their current habitat. We studied plant-to-plant dispersal of adult whiteflies in response to the presence of predatory mites on the plant on which the whiteflies were released. These predators attack whitefly eggs and crawlers, but not the adults, which can fly to other plants and can learn to avoid plants with predators. Being tiny and wingless, the predatory mites are slow dispersers compared to adult whiteflies. This offers the whiteflies the opportunity to escape from plants with predatory mites to plants without predators, thus avoiding predation of their offspring. To test for this escape response, a greenhouse experiment was carried out, where whiteflies were released on the first of a row of 5 cucumber plants, 0.6 m or 2 m apart, and predators either on the same plant, on the next plant, or nowhere (control. Adult whiteflies dispersed significantly faster from plants with predatory mites onto neighbouring plants when the plants were 0.6 m apart, but not when plants were 2 m apart. However, the final numbers of whiteflies that had successfully dispersed at the end of the experiments did not differ significantly for either of the two interplant distances. Overall, the proportion of whiteflies that did disperse was low, suggesting that adult whiteflies were apparently reluctant to disperse, even from plants with predators. Our results suggest that this reluctance increases with the distance between the plants, so most likely depends on the uncertainty to find a new plant. Thus, whiteflies do not always venture to fly even when they can easily bridge the distance to another plant.

  8. Olfactory response of the predator Zetzellia mali to a prey patch occupied by a conspecific predator

    NARCIS (Netherlands)

    Zahedi-Golpayegani, A.; Saboori, A.; Sabelis, M.W.

    2007-01-01

    While searching for food, predators may use volatiles associated with their prey, but also with their competitors for prey. This was tested for the case of Zetzellia mali (Ewing) (Acari: Stigmaeidae), an important predator of the hawthorn spider mite, Amphitetranychus viennensis (Zacher) (Acari:

  9. The influence of generalist predators in spatially extended predator-prey systems

    DEFF Research Database (Denmark)

    Chakraborty, Subhendu

    2015-01-01

    The presence of generalist predators is known to have important ecological impacts in several fields. They have wide applicability in the field of biological control. However, their role in the spatial distribution of predator and prey populations is still not clear. In this paper, the spatial dy...

  10. Predator-induced changes in metabolism cannot explain the growth/predation risk tradeoff.

    Directory of Open Access Journals (Sweden)

    Ulrich K Steiner

    2009-07-01

    Full Text Available Defence against predators is usually accompanied by declining rates of growth or development. The classical growth/predation risk tradeoff assumes reduced activity as the cause of these declines. However, in many cases these costs cannot be explained by reduced foraging effort or enhanced allocation to defensive structures under predation risk. Here, we tested for a physiological origin of defence costs by measuring oxygen consumption in tadpoles (Rana temporaria exposed to predation risk over short and long periods of time. The short term reaction was an increase in oxygen consumption, consistent with the "fight-or-flight" response observed in many organisms. The long term reaction showed the opposite pattern: tadpoles reduced oxygen consumption after three weeks exposure to predators, which would act to reduce the growth cost of predator defence. The results point to an instantaneous and reversible stress response to predation risk. This suggests that the tradeoff between avoiding predators and growing rapidly is not caused by changes in metabolic rate, and must be sought in other behavioural or physiological processes.

  11. Novel predators emit novel cues: a mechanism for prey naivety towards alien predators.

    Science.gov (United States)

    Carthey, Alexandra J R; Bucknall, Martin P; Wierucka, Kaja; Banks, Peter B

    2017-11-27

    Detecting enemies is crucial for survival and a trait that develops over an evolutionary timeframe. Introduced species disrupt coevolved systems of communication and detection in their new ranges, often leading to devastating impacts. The classic example is prey naivety towards alien predators, whereby prey fail to recognise a new predator. Yet exactly why native prey fail to recognise alien predators remains puzzling. Naivety theory predicts that it is because novel predators emit novel cues. Distantly related animals have distinct evolutionary histories, physiologies and ecologies, predicting they will emit different cues. Yet it also possible that all predators emit similar cues because they are carnivorous. We investigate whether odour cues differ between placental and marsupial carnivores in Australia, where native prey experienced only marsupial mammal predation until ~4000 years ago. We compared volatile chemical profiles of urine, scats and bedding from four placental and three marsupial predators. Chemical profiles showed little overlap between placental and marsupial carnivores across all odour types, suggesting that cue novelty is a plausible mechanism for prey naivety towards alien predators. Our results also suggest a role for olfactory cues to complement visual appearance and vocalisations as biologically meaningful ways to differentiate species.

  12. Do Predation Rates on Artificial Nests Accurately Reflect Predation Rates on Natural Bird Nests?

    Science.gov (United States)

    David I. King; Richard M. DeGraaf; Curtice R. Griffin; Thomas J. Maier

    1999-01-01

    Artificial nests are widely used in avian field studies. However, it is unclear how well predation rates on artificial nests reflect predation rates on natural nests. Therefore, we compared survival rates of artificial nests (unused natural nests baited with House Sparrow eggs) with survival rates of active bird nests in the same habitat at the same sites. Survival...

  13. Predator-induced changes in metabolism cannot explain the growth/predation risk tradeoff

    DEFF Research Database (Denmark)

    Steiner, Uli; Van Buskirk, Josh

    2009-01-01

    allocation to defensive structures under predation risk. Here, we tested for a physiological origin of defence costs by measuring oxygen consumption in tadpoles (Rana temporaria) exposed to predation risk over short and long periods of time. The short term reaction was an increase in oxygen consumption...

  14. A predator-2 prey fast-slow dynamical system for rapid predator evolution

    DEFF Research Database (Denmark)

    Piltz, Sofia Helena; Veerman, Frits; Maini, Philip K.

    2017-01-01

    We consider adaptive change of diet of a predator population that switches its feeding between two prey populations. We develop a novel 1 fast-3 slow dynamical system to describe the dynamics of the three populations amidst continuous but rapid evolution of the predator's diet choice. The two ext...

  15. Vertebrate predator-prey interactions in a seasonal environment

    DEFF Research Database (Denmark)

    Schmidt, Niels Martin; Berg, Thomas B; Forchhammer, Mads

    2008-01-01

    in Zackenbergdalen. Despite large differences in relative predator densities between these two locations, the two lemming populations exhibit remarkably similar and synchronous population fluctuations. Also, in both lemming populations the annual fluctuations seem primarily driven by a 1-year delay in stoat Mustela...... erminea predation and stabilising predation from the generalist predators, in Zackenbergdalen mainly the arctic fox Alopex lagopus. In Zackenbergdalen, however, the coupling between the specialist stoat and the lemming population is relatively weak. During summer, the predation pressure is high...... winters, predation by the only remaining predator, the stoat, is insufficient to regulate the lemming population. In the predator-lemming model, seasonality plays an important role in determining the. growth rate of the lemming population as well as the density of the various lemming predators. We...

  16. Forest fragmentation and rhinocryptid nest predation in central Chile

    Science.gov (United States)

    Vergara, Pablo M.; Simonetti, Javier A.

    2003-12-01

    Fragmentation of forest landscapes can raise the intensity of nest predation by increasing the abundance and richness of generalist or introduced predators. Understory foraging birds, such as rhinocryptids, can be highly vulnerable to nest predation in fragmented landscapes because they often place their nests on the ground. Temperate deciduous forests in Chile have been intensively fragmented in the last centuries, causing changes in nest predator densities. We tested if predation of artificial nests, mimicking those of rhinocryptids, placed on and above ground was higher in the remnant fragments of central Chile due to an increase in predator abundance. The rate of nest predation in forest remnants was larger than in native continuous forest. Small mammals were the main nest predators. Despite high predation rates, the abundance of rhinocryptids is higher in forest remnants, suggesting that fragments might constitute ecological traps.

  17. Importance of the predator's ecological neighborhood in modeling predation on migrating prey

    Science.gov (United States)

    DeAngelis, Donald L.; Petersen, James H.

    2001-01-01

    Most mathematical descriptions of predator-prey interactions fail to take into account the spatio-temporal structures of the populations, which can lead to errors or misinterpretations. For example, a compact pulse of prey migrating through a field of quasi-stationary predators may not be well described by standard predator-prey models, because the predators and prey are unlikely to be well mixed; that is, the prey may be exposed to only a fraction of the predator population at a time. This underscores the importance of properly accounting for the ecological neighborhood, or effective feeding range, of predators in models. We illustrate this situation with a series of models of salmon smolts migrating through a reservoir arrayed with predators. The reservoir is divided into a number of longitudinal compartments or spatial cells, the length of each cell representing the upstream-downstream range over which predators can forage. In this series of models a 100-km-long reservoir is divided, successively into 2, 5, 10, 25, 50, 100, 200, and 400 cells, with respective cell lengths of 50, 20, 10, 4, 2, 1, 0.5, and 0.25 km. We used a detailed individual-based simulation model at first, but to ensure robustness of results we supplemented this with a simple analytic model. Both models showed sharp differences in the predicted mortality to a compact pulse of smolt prey moving through the reservoir, depending on the number of spatial cells in the model. In particular, models with fewer than about 10 cells vastly overpredicted the amount of mortality due to predators with activity ranges of not more than a few kilometers. These results corroborate recent theoretical and simulation studies on the importance of spatial scale and behavior in modeling predator-prey dynamics.

  18. The START III bargaining space

    Energy Technology Data Exchange (ETDEWEB)

    Karas, T.H.

    1998-08-01

    The declining state of the Russian military and precarious Russian economic condition will give the US considerable advantages at the START III bargaining table. Taking the US-RF asymmetries into account, this paper discusses a menu of START III measures the US could ask for, and measures it could offer in return, in attempting to negotiate an equitable treaty. Measures the US might seek in a START III treaty include: further reductions in deployed strategic nuclear warheads, irreversibility of reductions through warhead dismantlement; beginning to bring theater nuclear weapons under mutual control, and increased transparency into the Russian nuclear weapons complex. The US may, however, wish to apply its bargaining advantages to attempting to achieve the first steps toward two long-range goals that would enhance US security: bringing theater nuclear weapons into the US-RF arms control arena, and increasing transparency into the Russian nuclear weapons complex. In exchange for measures relating to these objectives, the US might consider offering to Russia: Further strategic weapons reductions approaching levels at which the Russians believe they could maintain a degree of parity with the US; Measures to decrease the large disparities in potential deliver-system uploading capabilities that appear likely under current START II/START III scenarios; and Financial assistance in achieving START II/START III reductions as rapidly as is technically possible.

  19. Inducible defenses in prey intensify predator cannibalism.

    Science.gov (United States)

    Kishida, Osamu; Trussell, Geoffrey C; Nishimura, Kinya; Ohgushi, Takayuki

    2009-11-01

    Trophic cascades are often a potent force in ecological communities, but abiotic and biotic heterogeneity can diffuse their influence. For example, inducible defenses in many species create variation in prey edibility, and size-structured interactions, such as cannibalism, can shift predator diets away from heterospecific prey. Although both factors diffuse cascade strength by adding heterogeneity to trophic interactions, the consequences of their interactioh remain poorly understood. We show that inducible defenses in tadpole prey greatly intensify cannibalism in predatory larval salamanders. The likelihood of cannibalism was also strongly influenced by asymmetries in salamander size that appear to be most important in the presence of defended prey. Hence, variation in prey edibility and the size structure of the predator may synergistically affect predator-prey population dynamics by reducing prey mortality and increasing predator mortality via cannibalism. We also suggest that the indirect effects of prey defenses may shape the evolution of predator traits that determine diet breadth and how trophic dynamics unfold in natural systems.

  20. Universal Design: Places to Start

    National Research Council Canada - National Science Library

    Jay Dolmage

    2015-01-01

    Beginning with a series of possible ways to introduce an essay on Universal Design for Learning, this contribution instead resolves to offer a long listing or inventory of different places to start...

  1. Predator detection and evasion by flying insects.

    Science.gov (United States)

    Yager, David D

    2012-04-01

    Echolocating bats detect prey using ultrasonic pulses, and many nocturnally flying insects effectively detect and evade these predators through sensitive ultrasonic hearing. Many eared insects can use the intensity of the predator-generated ultrasound and the stereotyped progression of bat echolocation pulse rate to assess risk level. Effective responses can vary from gentle turns away from the threat (low risk) to sudden random flight and dives (highest risk). Recent research with eared moths shows that males will balance immediate bat predation risk against reproductive opportunity as judged by the strength and quality of conspecific pheromones present. Ultrasound exposure may, in fact, bias such decisions for up to 24 hours through plasticity in the CNS olfactory system. However, brain processing of ultrasonic stimuli to yield adaptive prey behaviors remains largely unstudied, so possible mechanisms are not known. Copyright © 2011 Elsevier Ltd. All rights reserved.

  2. Minimizing predation risk in a landscape of multiple predators: effects on the spatial distribution of African ungulates.

    Science.gov (United States)

    Thaker, Maria; Vanak, Abi T; Owen, Cailey R; Ogden, Monika B; Niemann, Sophie M; Slotow, Rob

    2011-02-01

    Studies that focus on single predator-prey interactions can be inadequate for understanding antipredator responses in multi-predator systems. Yet there is still a general lack of information about the strategies of prey to minimize predation risk from multiple predators at the landscape level. Here we examined the distribution of seven African ungulate species in the fenced Karongwe Game Reserve (KGR), South Africa, as a function of predation risk from all large carnivore species (lion, leopard, cheetah, African wild dog, and spotted hyena). Using observed kill data, we generated ungulate-specific predictions of relative predation risk and of riskiness of habitats. To determine how ungulates minimize predation risk at the landscape level, we explicitly tested five hypotheses consisting of strategies that reduce the probability of encountering predators, and the probability of being killed. All ungulate species avoided risky habitats, and most selected safer habitats, thus reducing their probability of being killed. To reduce the probability of encountering predators, most of the smaller prey species (impala, warthog, waterbuck, kudu) avoided the space use of all predators, while the larger species (wildebeest, zebra, giraffe) only avoided areas where lion and leopard space use were high. The strength of avoidance for the space use of predators generally did not correspond to the relative predation threat from those predators. Instead, ungulates used a simpler behavioral rule of avoiding the activity areas of sit-and-pursue predators (lion and leopard), but not those of cursorial predators (cheetah and African wild dog). In general, selection and avoidance of habitats was stronger than avoidance of the predator activity areas. We expect similar decision rules to drive the distribution pattern of ungulates in other African savannas and in other multi-predator systems, especially where predators differ in their hunting modes.

  3. Predator diversity effects in an exotic freshwater food web.

    Directory of Open Access Journals (Sweden)

    Rahmat Naddafi

    Full Text Available Cascading trophic interactions are often defined as the indirect effects of a predator on primary producers through the effect of the predator on herbivores. These effects can be both direct through removal of herbivores [density-mediated indirect interactions (DMIIs] or indirect through changes in the behavior of the herbivores [trait-mediated indirect interactions (TMIIs]. How the relative importance of these two indirect interactions varies with predator diversity remains poorly understood. We tested the effect of predator diversity on both TMIIs and DMIIs on phytoplankton using two competitive invasive dreissenid mussel species (zebra mussel and quagga mussel as the herbivores and combinations of one, two or all three species of the predators pumpkinseed sunfish, round goby, and rusty crayfish. Predators had either direct access to mussels and induced both TMII and DMII, or no direct access and induced only TMII through the presence of risk cues. In both sets of treatments, the predators induced a trophic cascade which resulted in more phytoplankton remaining with predators present than with only mussels present. The trophic cascade was weaker in three-predator and two-predator treatments than in one-predator treatments when predators had direct access to dreissenids (DMIIs and TMIIs. Crayfish had higher cascading effects on phytoplankton than both pumpkinseed and round goby. Increased predator diversity decreased the strength of DMIIs but had no effect on the strength of TMIIs. The strength of TMIIs was higher with zebra than quagga mussels. Our study suggests that inter-specific interference among predators in multi-species treatments weakens the consumptive cascading effects of predation on lower trophic levels whereas the importance of predator diversity on trait mediated effects depends on predator identity.

  4. Predator identity and additive effects in a treehole community.

    Science.gov (United States)

    Griswold, Marcus W; Lounibos, L Philip

    2006-04-01

    Multiple predator species can interact as well as strongly affect lower trophic levels, resulting in complex, nonadditive effects on prey populations and community structure. Studies of aquatic systems have shown that interactive effects of predators on prey are not necessarily predictable from the direct effects of each species alone. To test for complex interactions, the individual and combined effects of a top and intermediate predator on larvae of native and invasive mosquito prey were examined in artificial analogues of water-filled treeholes. The combined effects of the two predators were accurately predicted from single predator treatments by a multiplicative risk model, indicating additivity. Overall survivorship of both prey species decreased greatly in the presence of the top predator Toxorhynchites rutilus. By itself, the intermediate predator Corethrella appendiculata increased survivorship of the native prey species Ochlerotatus triseriatus and decreased survivorship of the invasive prey species Aedes albopictus relative to treatments without predators. Intraguild predation did not occur until alternative prey numbers had been reduced by approximately one-half. Owing to changes in size structure accompanying its growth, T. rutilus consumed more prey as time progressed, whereas C. appendiculata consumed less. The intermediate predator, C. appendiculata, changed species composition by preferentially consuming A. albopictus, while the top predator, T. rutilus, reduced prey density, regardless of species. Although species interactions were in most cases predicted from pairwise interactions, risk reduction from predator interference occurred when C. appendiculata densities were increased and when the predators were similarly sized.

  5. PREDATOR IDENTITY AND ADDITIVE EFFECTS IN A TREEHOLE COMMUNITY

    Science.gov (United States)

    Griswold, Marcus W.; Lounibos, L. Philip

    2007-01-01

    Multiple predator species can interact as well as strongly affect lower trophic levels, resulting in complex, nonadditive effects on prey populations and community structure. Studies of aquatic systems have shown that interactive effects of predators on prey are not necessarily predictable from the direct effects of each species alone. To test for complex interactions, the individual and combined effects of a top and intermediate predator on larvae of native and invasive mosquito prey were examined in artificial analogues of water-filled treeholes. The combined effects of the two predators were accurately predicted from single predator treatments by a multiplicative risk model, indicating additivity. Overall survivorship of both prey species decreased greatly in the presence of the top predator Toxorhynchites rutilus. By itself, the intermediate predator Corethrella appendiculata increased survivorship of the native prey species Ochlerotatus triseriatus and decreased survivorship of the invasive prey species Aedes albopictus relative to treatments without predators. Intraguild predation did not occur until alternative prey numbers had been reduced by approximately one-half. Owing to changes in size structure accompanying its growth, T. rutilus consumed more prey as time progressed, whereas C. appendiculata consumed less. The intermediate predator, C. appendiculata, changed species composition by preferentially consuming A. albopictus, while the top predator, T. rutilus, reduced prey density, regardless of species. Although species interactions were in most cases predicted from pairwise interactions, risk reduction from predator interference occurred when C. appendiculata densities were increased and when the predators were similarly sized. PMID:16676542

  6. Effects Of Predator Exclosures On Nesting Success Of Killdeer

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Nests of shorebirds are often destroyed by predators and in some instances predation may cause severe local declines in breeding success and in size of a breeding...

  7. 2005 nest success data : Klettke WPA predator exclosure

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Report summarizing nest success at Klettke Waterfowl Production Area predator exclosure on Kulm wetland Management District in 2005. In 2005, the Klettke predator...

  8. Generalization of predator recognition: Velvet geckos display anti-predator behaviours in response to chemicals from non-dangerous elapid snakes

    OpenAIRE

    Jonathan K. WEBB, Weiguo DU, David PIKE, Richard SHINE

    2010-01-01

    Many prey species detect chemical cues from predators and modify their behaviours in ways that reduce their risk of predation. Theory predicts that prey should modify their anti-predator responses according to the degree of threat posed by the predator. That is, prey should show the strongest responses to chemicals of highly dangerous prey, but should ignore or respond weakly to chemicals from non-dangerous predators. However, if anti-predator behaviours are not costly, and predators are rare...

  9. Predator diversity hotspots in the blue ocean.

    Science.gov (United States)

    Worm, Boris; Lotze, Heike K; Myers, Ransom A

    2003-08-19

    Concentrations of biodiversity, or hotspots, represent conservation priorities in terrestrial ecosystems but remain largely unexplored in marine habitats. In the open ocean, many large predators such as tunas, sharks, billfishes, and sea turtles are of current conservation concern because of their vulnerability to overfishing and ecosystem role. Here we use scientific-observer records from pelagic longline fisheries in the Atlantic and Pacific Oceans to show that oceanic predators concentrate in distinct diversity hotspots. Predator diversity consistently peaks at intermediate latitudes (20-30 degrees N and S), where tropical and temperate species ranges overlap. Individual hotspots are found close to prominent habitat features such as reefs, shelf breaks, or seamounts and often coincide with zooplankton and coral reef hotspots. Closed-area models in the northwest Atlantic predict that protection of hotspots outperforms other area closures in safeguarding threatened pelagic predators from ecological extinction. We conclude that the seemingly monotonous landscape of the open ocean shows rich structure in species diversity and that these features should be used to focus future conservation efforts.

  10. Predation of Myrmeleon obscurus (Navas, 1912) (neuroptera ...

    African Journals Online (AJOL)

    ... removal of mandibles and abandonment of remains of the prey. Maximizing predation is a strategy for these seasonal insects to store energy that might help them to survive during the unfavourable rainy season. © 2010 International Formulae Group. All rights reserved. Keywords: Ant lion larvae, Cameroon, mandibles, ...

  11. Sexually Violent Predators and Civil Commitment Laws

    Science.gov (United States)

    Beyer Kendall, Wanda D.; Cheung, Monit

    2004-01-01

    This article analyzes the civil commitment models for treating sexually violent predators (SVPs) and analyzes recent civil commitment laws. SVPs are commonly defined as sex offenders who are particularly predatory and repetitive in their sexually violent behavior. Data from policy literature, a survey to all states, and a review of law review…

  12. PREDATOR IN THE DEMOCRATIC REPUBLIC OF CONGO

    African Journals Online (AJOL)

    But its dispersal was constrained by intense consumption and trade of young tender cassava leaves, the natural habitat of the predator. A negative and significant correlation was found between the incidence of the harvest and the plants with T. aripo. Harvesting at 30, 45 and 60 days interval led to population densities of T.

  13. Climate change and marine top predators

    DEFF Research Database (Denmark)

    Climate change affects all components of marine ecosystems. For endothermic top predators, i.e. seabirds and marine mammals, these impacts are often complex and mediated through trophic relationships. In this Research Topic, leading researchers attempt to identify patterns of change among seabirds...

  14. What regulates crab predation on mangrove propagules?

    Science.gov (United States)

    Van Nedervelde, Fleur; Cannicci, Stefano; Koedam, Nico; Bosire, Jared; Dahdouh-Guebas, Farid

    2015-02-01

    Crabs play a major role in some ecosystems. To increase our knowledge about the factors that influence crab predation on propagules in mangrove forests, we performed experiments in Gazi Bay, Kenya in July 2009. We tested whether: (1) crab density influences propagule predation rate; (2) crab size influences food competition and predation rate; (3) crabs depredate at different rates according to propagule and canopy cover species; (4) vegetation density is correlated with crab density; (5) food preferences of herbivorous crabs are determined by size, shape and nutritional value. We found that (1) propagule predation rate was positively correlated to crab density. (2) Crab competitive abilities were unrelated to their size. (3) Avicennia marina propagules were consumed more quickly than Ceriops tagal except under C. tagal canopies. (4) Crab density was negatively correlated with the density of A. marina trees and pneumatophores. (5) Crabs prefer small items with a lower C:N ratio. Vegetation density influences crab density, and crab density affects propagule availability and hence vegetation recruitment rate. Consequently, the mutual relationships between vegetation and crab populations could be important for forest restoration success and management.

  15. Bioeconomic modelling of a prey predator system using differential ...

    African Journals Online (AJOL)

    Bioeconomic modelling of a prey predator system using differential algebraic equations. ... International Journal of Engineering, Science and Technology ... We propose a biological economic model based on prey-predator dynamics where the prey species are continuously harvested and predation is considered with type II ...

  16. Bird's nesting success and eggs predation within Arusa National ...

    African Journals Online (AJOL)

    Nesting success and eggs predation is among the factors that affect the population dynamics of bird species. The study was carried out to determine predation impact on selected bird species population in Arusha National Park, Arusha, Tanzania. Specifically the study assessed the potential predators to ground (Scaly ...

  17. Selective predation and prey class behaviour as possible ...

    African Journals Online (AJOL)

    To test these mechanisms, a study was conducted on Samara Private Game Reserve to investigate the potential impact cheetah (Acinonyx jubatus) predation has had on the kudu (Tragelaphus strepciseros) population. Kudu age and sex data were collected across both predator-present and predator-absent sections using ...

  18. Predator personality and prey behavioural predictability jointly determine foraging performance.

    Science.gov (United States)

    Chang, Chia-Chen; Teo, Huey Yee; Norma-Rashid, Y; Li, Daiqin

    2017-01-17

    Predator-prey interactions play important roles in ecological communities. Personality, consistent inter-individual differences in behaviour, of predators, prey or both are known to influence inter-specific interactions. An individual may also behave differently under the same situation and the level of such variability may differ between individuals. Such intra-individual variability (IIV) or predictability may be a trait on which selection can also act. A few studies have revealed the joint effect of personality types of both predators and prey on predator foraging performance. However, how personality type and IIV of both predators and prey jointly influence predator foraging performance remains untested empirically. Here, we addressed this using a specialized spider-eating jumping spider, Portia labiata (Salticidae), as the predator, and a jumping spider, Cosmophasis umbratica, as the prey. We examined personality types and IIVs of both P. labiata and C. umbratica and used their inter- and intra-individual behavioural variation as predictors of foraging performance (i.e., number of attempts to capture prey). Personality type and predictability had a joint effect on predator foraging performance. Aggressive predators performed better in capturing unpredictable (high IIV) prey than predictable (low IIV) prey, while docile predators demonstrated better performance when encountering predictable prey. This study highlights the importance of the joint effect of both predator and prey personality types and IIVs on predator-prey interactions.

  19. Harvesting and Conversation in a Predator-Prey System

    NARCIS (Netherlands)

    Hoekstra, Jeljer; Bergh, van den Jeroen C.J.M.

    2001-01-01

    Optimal harvesting of prey in a predator-prey ecosystem is studiedunder the condition that the existence of the predator has value. Predators (birds) and humans (fishers) compete for prey (shellfish). The behavior of the system is studied and conditions for optimal control are deduced. Various

  20. Determining sensitive stages for learning to detect predators in ...

    Indian Academy of Sciences (India)

    2014-07-10

    Jul 10, 2014 ... 2012) to determine if learning also plays a role in predator detection. The streams and rivulets that harbour S. temporalis tadpoles are also home to a diverse community of predators. In such diverse, seasonally varying predatory environment, reliance solely on innate predator detection mechanisms could ...

  1. Spider mite web mediates anti-predator behaviour

    NARCIS (Netherlands)

    Lemos, F.; de Almeida Sarmento, R.; Pallini, A.; Rosa Dias, C.; Sabelis, M.W.; Janssen, A.

    2010-01-01

    Herbivores suffer significant mortality from predation and are therefore subject to natural selection on traits promoting predator avoidance and resistance. They can employ an array of strategies to reduce predation, for example through changes in behaviour, morphology and life history. So far, the

  2. Perceived predation risk as a function of predator dietary cues in terrestrial salamanders.

    Science.gov (United States)

    Murray; Jenkins

    1999-01-01

    Prey often avoid predator chemical cues, and in aquatic systems, prey may even appraise predation risk via cues associated with the predator's diet. However, this relationship has not been shown for terrestrial predator-prey systems, where the proximity of predators and prey, and the intensity of predator chemical cues in the environment, may be less than in aquatic systems. In the laboratory, we tested behavioural responses (avoidance, habituation and activity) of terrestrial red-backed salamanders, Plethodon cinereus, to chemical cues from garter snakes, Thamnophis sirtalis, fed either red-backed salamanders or earthworms (Lumbricus spp.). We placed salamanders in arenas lined with paper towels pretreated with snake chemicals, and monitored salamander movements during 120 min. Salamanders avoided substrates preconditioned by earthworm-fed (avoidanceX+/-SE=91.1+/-2.5%, N=25) and salamander-fed (95.2+/-2.5%, N=25) snakes, when tested against untreated substrate (control). Salamanders avoided cues from salamander-fed snakes more strongly (75.2+/-5.5%, N=25) than earthworm-fed snakes when subjected to both treatments simultaneously, implying that salamanders were sensitive to predator diet. Salamanders tended to avoid snake substrate more strongly during the last 60 min of a trial, but activity patterns were similar between salamanders exposed exclusively to control substrate versus those subject to snake cues. In another experiment, salamanders failed to avoid cues from dead conspecifics, suggesting that the stronger avoidance of salamander-fed snakes in the previous experiment was not directly due to chemical cues emitted by predator-killed salamanders. Salamanders also did not discriminate between cues from a salamander-fed snake versus a salamander-fed snake that was recently switched (i.e. diet. Our results imply that terrestrial salamanders are sensitive to perceived predation risk via by-products of predator diet, and that snake predators rather than dead

  3. Spatial ecology of predator-prey interactions: corridors and patch shape influence seed predation.

    Energy Technology Data Exchange (ETDEWEB)

    J. L . Orrock; B. J. Danielson; M. J. Burns; D. J. Levey

    2003-02-03

    J.L. Orrock, B.J. Danielson, M.J. Burns, and D.J. Levey. 2003. Spatial ecology of predator-prey interactions: corridors and patch shape influence seed predation. Ecology, 84(10):2589-2599. Abstract: Corridors that connect patches of disjunct habitat may be promising tools for mediating the negative impacts of habitat fragmentation, but little is known about how corridors affect ecological interactions. In eight 12-ha experimental landscapes, we examined how corridors affect the impact of invertebrate, rodent, and avian seed predators on pokeweed, Phytolacca americana. Over 13 months in 2000 and 2001, we quantified the effects of patch shape, connectivity, and predator type on the number of seeds germinating in the field (germinants), seed removal, and the viability of remaining seeds. Corridors did not affect the number of P. americana germinants in experimental exclosures or the viability of seeds remaining in exclosures. However, corridors affected the removal of seeds in a predator-specific manner: invertebrates removed more seeds in unconnected patches, whereas rodents removed more seeds in connected patches. Seed removal by birds was similar in connected and unconnected patches. Total seed removal by all seed predators was not affected by corridors, because invertebrates removed more seeds where rodents removed fewer seeds, and vice versa. Overall, seed predation signi®cantly reduced the number and viability of remaining seeds, and reduced the number of germinants in 2000 but not in 2001. The abundance of naturally occurring P. americana plants in our experimental patches in 2000 decreased with increasing seed removal from exclosures but was not related to viability or germinants in 2000, suggesting that seed removal may shape the distribution and abundance of this species. Complementary patterns of seed removal by rodents and invertebrates suggest that corridors alter the effects of these predator taxa by changing the relative amounts of edge and core

  4. Unidirectional prey–predator facilitation: apparent prey enhance predators' foraging success on cryptic prey

    OpenAIRE

    Zhang, Yixin; Richardson, John S

    2007-01-01

    Food availability can strongly affect predator–prey dynamics. When change in habitat condition reduces the availability of one prey type, predators often search for other prey, perhaps in a different habitat. Interactions between behavioural and morphological traits of different prey may influence foraging success of visual predators through trait-mediated indirect interactions (TMIIs), such as prey activity and body coloration. We tested the hypothesis that foraging success of stream-dwellin...

  5. Stress triangle: do introduced predators exert indirect costs on native predators and prey?

    Directory of Open Access Journals (Sweden)

    Jennifer R Anson

    Full Text Available Non-consumptive effects of predators on each other and on prey populations often exceed the effects of direct predation. These effects can arise from fear responses elevating glucocorticoid (GC hormone levels (predator stress hypothesis or from increased vigilance that reduces foraging efficiency and body condition (predator sensitive foraging hypothesis; both responses can lead to immunosuppression and increased parasite loads. Non-consumptive effects of invasive predators have been little studied, even though their direct impacts on local species are usually greater than those of their native counterparts. To address this issue, we explored the non-consumptive effects of the invasive red fox Vulpes vulpes on two native species in eastern Australia: a reptilian predator, the lace monitor Varanus varius and a marsupial, the ringtail possum Pseudocheirus peregrinus. In particular, we tested predictions derived from the above two hypotheses by comparing the basal glucocorticoid levels, foraging behaviour, body condition and haemoparasite loads of both native species in areas with and without fox suppression. Lace monitors showed no GC response or differences in haemoparasite loads but were more likely to trade safety for higher food rewards, and had higher body condition, in areas of fox suppression than in areas where foxes remained abundant. In contrast, ringtails showed no physiological or behavioural differences between fox-suppressed and control areas. Predator sensitive foraging is a non-consumptive cost for lace monitors in the presence of the fox and most likely represents a response to competition. The ringtail's lack of response to the fox potentially represents complete naiveté or strong and rapid selection to the invasive predator. We suggest evolutionary responses are often overlooked in interactions between native and introduced species, but must be incorporated if we are to understand the suite of forces that shape community

  6. Cascading effects of predation risk determine how marine predators become terrestrial prey on an oceanic island.

    Science.gov (United States)

    Thomsen, Sarah K; Green, David J

    2016-12-01

    Apex predators can suppress the foraging activity of mesopredators, which may then result in cascading benefits for the prey of those mesopredators. We studied the interactions between a top predator, the Barn Owl (Tyto alba), and their primary prey, an island endemic deer mouse (Peromyscus maniculatus elusus), which in turn consumes the eggs of seabirds nesting on Santa Barbara Island in California. Scripps's Murrelets (Synthliboramphus scrippsi), a threatened nocturnal seabird, arrive annually to breed on this island, and whose first egg is particularly vulnerable to predation by mice. We took advantage of naturally occurring extreme variations in the density of mice and owls on the island over 3 years and predicted that (1) mouse foraging would decrease with increasing predation risk from owls and moonlight and (2) these decreases in foraging would reduce predation on murrelet eggs. We measured the giving up densities of mice with experimental foraging stations and found that mice were sensitive to predation risk and foraged less when owls were more abundant and less during the full moon compared to the new moon. We also monitored the fates of 151 murrelet eggs, and found that murrelet egg predation declined as owl abundance increased, and was lower during the full moon compared to the new moon. Moreover, high owl abundance suppressed egg predation even when mice were extremely abundant. We conclude that there is a behaviorally mediated cascade such that owls on the island had a positive indirect effect on murrelet egg survival. Our study adds to the wider recognition of the strength of risk effects to structure food webs, as well as highlighting the complex ways that marine and terrestrial food webs can intersect. © 2016 by the Ecological Society of America.

  7. Dynamics of a Diffusive Predator-Prey Model with Allee Effect on Predator

    Directory of Open Access Journals (Sweden)

    Xiaoqin Wang

    2013-01-01

    Full Text Available The reaction-diffusion Holling-Tanner prey-predator model considering the Allee effect on predator, under zero-flux boundary conditions, is discussed. Some properties of the solutions, such as dissipation and persistence, are obtained. Local and global stability of the positive equilibrium and Turing instability are studied. With the help of the numerical simulations, the rich Turing patterns, including holes, stripes, and spots patterns, are obtained.

  8. Predation of Five Generalist Predators on Brown Planthopper (Nilaparvata lugens Stål

    Directory of Open Access Journals (Sweden)

    Sri Karindah

    2015-09-01

    Full Text Available Two generalist predators of brown planthopper,Metioche vittaticollis and Anaxipha longipennis (Gryllidae have not been much studied in Indonesia. This research was conducted to study and compare the predatory ability of M. vittaticollis, A. longipennis (Gryllidae and three coleopterans, Paederus fuscipes (Staphylinidae, Ophionea sp. (Carabidae,and Micraspis sp. (Coccinellidae against brown planthopper (fourth and fifth instars under laboratory condition. In total, 20 nymphs of N. lugens were exposed for 2 hour to each predator for 5 consecutive days. Prey consumptions by the predatory crickets, M. vittaticollis and A. longipennis were greater than the other predators and followed by A. longipennis, Micraspis sp., P. fuscipes, and Ophionea sp. respectively. Consumption rates of M. vittaticolis and A. longipenis were also higher than other predators. Micraspis sp was more active on predation in the morning,while M. vittaticollis, A. longipennis, P. fuscipes, and Ophionea sp. were more active both in the morning and the night but not in the afternoon. However, all five species of predators were not so active in preying during the afternoon. In conclusion, a major effort should be extended to conserve these predatory crickets especially M. vittaticollis and A. longipennis.

  9. When to Start Antiretroviral Therapy

    Science.gov (United States)

    ... Drugs Clinical Trials Apps skip to content HIV Treatment Home Understanding HIV/AIDS Fact Sheets When to Start Antiretroviral Therapy Search ... Vaccine? What is a Preventive HIV Vaccine? HIV/AIDS Clinical Trials ... HIV Treatment HIV Treatment: The Basics Just Diagnosed: Next Steps ...

  10. Starting School: A Community Endeavor

    Science.gov (United States)

    Dockett, Sue; Perry, Bob

    2008-01-01

    Much of the current debate about children's transition to school focuses on children's readiness for school. Indeed, Boethel (2004, p. 17) describes transition as the "focal point of readiness." Typically, this focus extends to considering children's competencies--particularly their skills and abilities--at the time of starting school.…

  11. Off to a Good Start.

    Science.gov (United States)

    Hoffman, Carl

    1994-01-01

    Caring Start is a mobile-clinic program that provides prenatal care, well-baby clinics, childhood immunizations, counseling services, and contraceptives to rural poor families in northwest Pennsylvania. Before the mobile clinic, many rural women (mostly teenagers) went without prenatal health care due to lack of transportation. (LP)

  12. Revealing the role of predator interference in a predator-prey system with disease in prey population

    DEFF Research Database (Denmark)

    Chakraborty, Subhendu; Kooi, B.W.; Biswas, B.

    2015-01-01

    Predation on a species subjected to an infectious disease can affect both the infection level and the population dynamics. There is an ongoing debate about the act of managing disease in natural populations through predation. Recent theoretical and empirical evidence shows that predation on infec...

  13. Predation on artificial bird nests in chaparral fragments.

    Science.gov (United States)

    Langen, Tom A; Bolger, Douglas T; Case, Ted J

    1991-05-01

    The predation rate of artificial bird nests was measured in disturbed chaparral habitat fragments and at an unfragmented site in coastal San Diego County, California USA. Local extinctions of chaparral birds has been previously shown to occur in these fragments. The predation rate was highest at the unfragmented site. Among fragments, predation was higher at moderately disturbed than at highly disturbed sites. These results suggest that nest predator species diversity or density is reduced in disturbed chaparral fragments. Nest predation is probably not the most important cause of the observed loss of chaparral breeding bird diversity in these fragments.

  14. Climate change effects on predator-prey interactions.

    Science.gov (United States)

    Laws, Angela N

    2017-10-01

    Predator-prey interactions can be very important to community structure and function. A growing body of research demonstrates how climate change can modify these species interactions. Climate change can modify predator-prey interactions by affecting species characteristics, and by modifying consumptive and/or non-consumptive predator effects. Current work examines how climate change and predation risk can combine to influence herbivore stoichiometry and feeding ecology. Other recent advances show how climate change can affect chemical signaling of plants and insects, as well as how pollution and other components of the environmental context can modify predator-prey interactions. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Anthropogenic resource subsidies decouple predator-prey relationships.

    Science.gov (United States)

    Rodewald, Amanda D; Kearns, Laura J; Shustack, Daniel P

    2011-04-01

    The extent to which resource subsidies affect food web dynamics is poorly understood in anthropogenic landscapes. To better understand how species interactions are influenced by subsidies, we studied breeding birds and nest predators along a rural-to-urban landscape gradient that varied in subsidies provided to generalist predators. We hypothesized that resource subsidies in urban landscapes would decouple predator-prey relationships, as predators switch from natural to anthropogenic foods. From 2004 to 2009, we surveyed nest predators and monitored 2942 nests of five songbird species breeding in 19 mature forest stands in Ohio, USA. Eighteen species were video-recorded depredating nests. Numbers of avian and mammalian nest predators were positively associated with the amount of urban development surrounding forests, with the exception of Brown-headed Cowbirds (Molothrus ater). Although nest survival strongly declined with detections of nest predators in rural landscapes, nest survival and predator numbers were unrelated in urban landscapes. Thus, the strength of interaction between breeding birds and nest predators diminished as landscapes surrounding forested parks became more urbanized. Our work suggests that decoupling of predator-prey relationships can arise when synanthropic predators are heavily subsidized by anthropogenic resources. In this way, human drivers can alter, and completely disarticulate, relationships among species that are well established in more natural systems.

  16. Testing ecological and behavioral correlates of nest predation

    Science.gov (United States)

    Fontaine, J.J.; Martel, M.; Markland, H.M.; Niklison, Alina M.; Decker, Karie L.; Martin, T.E.

    2007-01-01

    Variation in nest predation rates among bird species are assumed to reflect differences in risk that are specific to particular nest sites. Theoretical and empirical studies suggest that parental care behaviors can evolve in response to nest predation risk and thereby differ among ecological conditions that vary in inherent risk. However, parental care also can influence predation risk. Separating the effects of nest predation risk inherent to a nest site from the risk imposed by parental strategies is needed to understand the evolution of parental care. Here we identify correlations between risks inherent to nest sites, and risk associated with parental care behaviors, and use an artificial nest experiment to assess site-specific differences in nest predation risk across nesting guilds and between habitats that differed in nest predator abundance. We found a strong correlation between parental care behaviors and inherent differences in nest predation risk, but despite the absence of parental care at artificial nests, patterns of nest predation risk were similar for real and artificial nests both across nesting guilds and between predator treatments. Thus, we show for the first time that inherent risk of nest predation varies with nesting guild and predator abundance independent of parental care. ?? Oikos.

  17. Effects of uniform rotational flow on predator-prey system

    Science.gov (United States)

    Lee, Sang-Hee

    2012-12-01

    Rotational flow is often observed in lotic ecosystems, such as streams and rivers. For example, when an obstacle interrupts water flowing in a stream, energy dissipation and momentum transfer can result in the formation of rotational flow, or a vortex. In this study, I examined how rotational flow affects a predator-prey system by constructing a spatially explicit lattice model consisting of predators, prey, and plants. A predation relationship existed between the species. The species densities in the model were given as S (for predator), P (for prey), and G (for plant). A predator (prey) had a probability of giving birth to an offspring when it ate prey (plant). When a predator or prey was first introduced, or born, its health state was assigned an initial value of 20 that subsequently decreased by one with every time step. The predator (prey) was removed from the system when the health state decreased to less than zero. The degree of flow rotation was characterized by the variable, R. A higher R indicates a higher tendency that predators and prey move along circular paths. Plants were not affected by the flow because they were assumed to be attached to the streambed. Results showed that R positively affected both predator and prey survival, while its effect on plants was negligible. Flow rotation facilitated disturbances in individuals’ movements, which consequently strengthens the predator and prey relationship and prevents death from starvation. An increase in S accelerated the extinction of predators and prey.

  18. Alcohol impairs predation risk response and communication in zebrafish.

    Directory of Open Access Journals (Sweden)

    Thiago Acosta Oliveira

    Full Text Available The effects of ethanol exposure on Danio rerio have been studied from the perspectives of developmental biology and behavior. However, little is known about the effects of ethanol on the prey-predator relationship and chemical communication of predation risk. Here, we showed that visual contact with a predator triggers stress axis activation in zebrafish. We also observed a typical stress response in zebrafish receiving water from these conspecifics, indicating that these fish chemically communicate predation risk. Our work is the first to demonstrate how alcohol effects this prey-predator interaction. We showed for the first time that alcohol exposure completely blocks stress axis activation in both fish seeing the predator and in fish that come in indirect contact with a predator by receiving water from these conspecifics. Together with other research results and with the translational relevance of this fish species, our data points to zebrafish as a promising animal model to study human alcoholism.

  19. Beyond Predation: The Zoophytophagous Predator Macrolophus pygmaeus Induces Tomato Resistance against Spider Mites.

    Directory of Open Access Journals (Sweden)

    Maria L Pappas

    Full Text Available Many predatory insects that prey on herbivores also feed on the plant, but it is unknown whether plants affect the performance of herbivores by responding to this phytophagy with defence induction. We investigate whether the prior presence of the omnivorous predator Macrolophus pygmaeus (Rambur on tomato plants affects plant resistance against two different herbivore species. Besides plant-mediated effects of M. pygmaeus on herbivore performance, we examined whether a plant defence trait that is known to be inducible by herbivory, proteinase inhibitors (PI, may also be activated in response to the interactions of this predator with the tomato plant. We show that exposing tomato plants to the omnivorous predator M. pygmaeus reduced performance of a subsequently infesting herbivore, the two-spotted spider mite Tetranychus urticae Koch, but not of the greenhouse whitefly Trialeurodes vaporariorum (Westwood. The spider-mite infested tomato plants experience a lower herbivore load, i.e., number of eggs deposited and individuals present, when previously exposed to the zoophytophagous predator. This effect is not restricted to the exposed leaf and persists on exposed plants for at least two weeks after the removal of the predators. The decreased performance of spider mites as a result of prior exposure of the plant to M. pygmaeus is accompanied by a locally and systemically increased accumulation of transcripts and activity of proteinase inhibitors that are known to be involved in plant defence. Our results demonstrate that zoophytophagous predators can induce plant defence responses and reduce herbivore performance. Hence, the suppression of populations of certain herbivores via consumption may be strengthened by the induction of plant defences by zoophytophagous predators.

  20. Predators vs. alien: differential biotic resistance to an invasive species by two resident predators

    Directory of Open Access Journals (Sweden)

    Calum MacNeil

    2013-10-01

    Full Text Available The success of invading species can be restricted by interspecific interactions such as competition and predation (i.e. biotic resistance from resident species, which may be natives or previous invaders. Whilst there are myriad examples of resident species preying on invaders, simply showing that such an interaction exists does not demonstrate that predation limits invader establishment, abundance or spread. Support for this conclusion requires evidence of negative associations between invaders and resident predators in the field and, further, that the predator-prey interaction is likely to strongly regulate or potentially de-stabilise the introduced prey population. Moreover, it must be considered that different resident predator species may have different abilities to restrict invaders. In this study, we show from analysis of field data that two European predatory freshwater amphipods, Gammarus pulex and G. duebeni celticus, have strong negative field associations with their prey, the invasive North American amphipod Crangonyx pseudogracilis. This negative field association is significantly stronger with G. pulex, a previous and now resident invader in the study sites, than with the native G. d. celticus. These field patterns were consistent with our experimental findings that both resident predators display potentially population de-stabilising Type II functional responses towards the invasive prey, with a significantly greater magnitude of response exhibited by G. pulex than by G. d. celticus. Further, these Type II functional responses were consistent across homo- and heterogeneous environments, contrary to the expectation that heterogeneity facilitates more stabilising Type III functional responses through the provision of prey refugia. Our experimental approach confirms correlative field surveys and thus supports the hypothesis that resident predatory invertebrates are differentially limiting the distribution and abundance of an

  1. Beyond Predation: The Zoophytophagous Predator Macrolophus pygmaeus Induces Tomato Resistance against Spider Mites.

    Science.gov (United States)

    Pappas, Maria L; Steppuhn, Anke; Geuss, Daniel; Topalidou, Nikoleta; Zografou, Aliki; Sabelis, Maurice W; Broufas, George D

    2015-01-01

    Many predatory insects that prey on herbivores also feed on the plant, but it is unknown whether plants affect the performance of herbivores by responding to this phytophagy with defence induction. We investigate whether the prior presence of the omnivorous predator Macrolophus pygmaeus (Rambur) on tomato plants affects plant resistance against two different herbivore species. Besides plant-mediated effects of M. pygmaeus on herbivore performance, we examined whether a plant defence trait that is known to be inducible by herbivory, proteinase inhibitors (PI), may also be activated in response to the interactions of this predator with the tomato plant. We show that exposing tomato plants to the omnivorous predator M. pygmaeus reduced performance of a subsequently infesting herbivore, the two-spotted spider mite Tetranychus urticae Koch, but not of the greenhouse whitefly Trialeurodes vaporariorum (Westwood). The spider-mite infested tomato plants experience a lower herbivore load, i.e., number of eggs deposited and individuals present, when previously exposed to the zoophytophagous predator. This effect is not restricted to the exposed leaf and persists on exposed plants for at least two weeks after the removal of the predators. The decreased performance of spider mites as a result of prior exposure of the plant to M. pygmaeus is accompanied by a locally and systemically increased accumulation of transcripts and activity of proteinase inhibitors that are known to be involved in plant defence. Our results demonstrate that zoophytophagous predators can induce plant defence responses and reduce herbivore performance. Hence, the suppression of populations of certain herbivores via consumption may be strengthened by the induction of plant defences by zoophytophagous predators.

  2. Getting started with Drupal commerce

    CERN Document Server

    Jones, Richard

    2013-01-01

    A simple yet concise step-by-step tutorial that starts from scratch and builds up your knowledge with focused examples that will enable you to set up and run an e-commerce website.This book is for beginners and will take you through the installation and configuration of Drupal Commerce from scratch, but some familiarity with Drupal 7 will be an advantage. All examples are based on development on a local computer - you do not need a hosted Drupal environment.

  3. Getting started with Twitter Flight

    CERN Document Server

    Hamshere, Tom

    2013-01-01

    Getting Started with Twitter Flight is written with the intention to educate the readers, helping them learn how to build modular powerful applications with Flight, Twitter's cutting-edge JavaScript framework.This book is for anyone with a foundation in JavaScript who wants to build web applications. Flight is quick and easy to learn, built on technologies you already understand such as the DOM, events, and jQuery.

  4. School start times for adolescents.

    Science.gov (United States)

    2014-09-01

    The American Academy of Pediatrics recognizes insufficient sleep in adolescents as an important public health issue that significantly affects the health and safety, as well as the academic success, of our nation's middle and high school students. Although a number of factors, including biological changes in sleep associated with puberty, lifestyle choices, and academic demands, negatively affect middle and high school students' ability to obtain sufficient sleep, the evidence strongly implicates earlier school start times (ie, before 8:30 am) as a key modifiable contributor to insufficient sleep, as well as circadian rhythm disruption, in this population. Furthermore, a substantial body of research has now demonstrated that delaying school start times is an effective countermeasure to chronic sleep loss and has a wide range of potential benefits to students with regard to physical and mental health, safety, and academic achievement. The American Academy of Pediatrics strongly supports the efforts of school districts to optimize sleep in students and urges high schools and middle schools to aim for start times that allow students the opportunity to achieve optimal levels of sleep (8.5-9.5 hours) and to improve physical (eg, reduced obesity risk) and mental (eg, lower rates of depression) health, safety (eg, drowsy driving crashes), academic performance, and quality of life. Copyright © 2014 by the American Academy of Pediatrics.

  5. Starting apparatus for internal combustion engines

    Science.gov (United States)

    Dyches, G.M.; Dudar, A.M.

    1995-01-01

    This report is a patent description for a system to start an internal combustion engine. Remote starting and starting by hearing impaired persons are addressed. The system monitors the amount of current being drawn by the starter motor to determine when the engine is started. When the engine is started the system automatically deactivates the starter motor. Five figures are included.

  6. The Great White Guppy: Top Predator

    Science.gov (United States)

    Michalski, G. M.

    2011-12-01

    Nitrogen isotopes are often used to trace the trophic level of members of an ecosystem. As part of a stable isotope biogeochemistry and forensics course at Purdue University, students are introduced to this concept by analyzing nitrogen isotopes in sea food purchased from local grocery stores. There is a systematic increase in 15N/14N ratios going from kelp to clams/shrimp, to sardines, to tuna and finally to shark. These enrichments demonstrate how nitrogen is enriched in biomass as predators consume prey. Some of the highest nitrogen isotope enrichments observed, however, are in the common guppy. We investigated a number of aquarium fish foods and find they typically have high nitrogen isotope ratios because they are made form fish meal that is produced primarily from the remains of predator fish such as tuna. From, a isotope perspective, the guppy is the top of the food chain, more ferocious than even the Great White shark.

  7. Hydrological disturbance diminishes predator control in wetlands.

    Science.gov (United States)

    Dorn, Nathan J; Cook, Mark I

    2015-11-01

    Effects of predators on prey populations can be especially strong in aquatic ecosystems, but disturbances may mediate the strength of predator limitation and even allow outbreaks of some prey populations. In a two-year study we investigated the numerical responses of crayfish (Procambarus fallax) and small fishes (Poeciliidae and Fundulidae) to a brief hydrological disturbance in replicated freshwater wetlands with an experimental drying and large predatory fish reduction. The experiment and an in situ predation assay tested the component of the consumer stress model positing that disturbances release prey from predator limitation. In the disturbed wetlands, abundances of large predatory fish were seasonally reduced, similar to dynamics in the Everglades (southern Florida). Densities of small fish were unaffected by the disturbance, but crayfish densities, which were similar across all wetlands before drying, increased almost threefold in the year after the disturbance. Upon re-flooding, juvenile crayfish survival was inversely related to the abundance of large fish across wetlands, but we found no evidence for enhanced algal food quality. At a larger landscape scale (500 km2 of the Everglades), crayfish densities over eight years were positively correlated with the severity of local dry disturbances (up to 99 days dry) during the preceding dry season. In contrast, densities of small-bodied fishes in the same wetlands were seasonally depressed by dry disturbances. The results from our experimental wetland drought and the observations of crayfish densities in the Everglades represent a large-scale example of prey population release following a hydrological disturbance in a freshwater ecosystem. The conditions producing crayfish pulses in the Everglades appear consistent with the mechanics of the consumer stress model, and we suggest crayfish pulses may influence the number of nesting wading birds in the Everglades.

  8. Range contraction in large pelagic predators.

    Science.gov (United States)

    Worm, Boris; Tittensor, Derek P

    2011-07-19

    Large reductions in the abundance of exploited land predators have led to significant range contractions for those species. This pattern can be formalized as the range-abundance relationship, a general macroecological pattern that has important implications for the conservation of threatened species. Here we ask whether similar responses may have occurred in highly mobile pelagic predators, specifically 13 species of tuna and billfish. We analyzed two multidecadal global data sets on the spatial distribution of catches and fishing effort targeting these species and compared these with available abundance time series from stock assessments. We calculated the effort needed to reliably detect the presence of a species and then computed observed range sizes in each decade from 1960 to 2000. Results suggest significant range contractions in 9 of the 13 species considered here (between 2% and 46% loss of observed range) and significant range expansions in two species (11-29% increase). Species that have undergone the largest declines in abundance and are of particular conservation concern tended to show the largest range contractions. These include all three species of bluefin tuna and several marlin species. In contrast, skipjack tuna, which may have increased its abundance in the Pacific, has also expanded its range size. These results mirror patterns described for many land predators, despite considerable differences in habitat, mobility, and dispersal, and imply ecological extirpation of heavily exploited species across parts of their range.

  9. Unmanned reconnaissance aircraft, Predator B in flight.

    Science.gov (United States)

    2001-01-01

    Predator B unmanned reconnaissance aircraft, shown here, under NASA's Environmental Research Aircraft and Sensor Technology (ERAST) project. ALTAIR/PREDATOR B -- General Atomics Aeronautical Systems, Inc., is developing the Altair version of its Predator B unmanned reconnaissance aircraft, shown here, under NASA's Environmental Research Aircraft and Sensor Technology (ERAST) project. NASA plans to use the Altair as a technology demonstrator testbed aircraft to validate a variety of command and control technologies for unmanned aerial vehicles (UAV), as well as demonstrate the capability to perform a variety of Earth science missions. The Altair is designed to carry an 700-lb. payload of scientific instruments and imaging equipment for as long as 32 hours at up to 52,000 feet altitude. Ten-foot extensions have been added to each wing, giving the Altair an overall wingspan of 84 feet with an aspect ratio of 23. It is powered by a 700-hp. rear-mounted TPE-331-10 turboprop engine, driving a three-blade propeller. Altair is scheduled to begin flight tests in the fourth quarter of 2002, and be acquired by NASA following successful completion of those basic airworthiness tests in early 2003 for evaluation of over-the-horizon control, detect, see and avoid and other technologies required to allow UAVs to operate safely with other aircraft in the national airspace.

  10. Egg predation in forest bird communities on islands and mainland.

    Science.gov (United States)

    Nilsson, Sven G; Björkman, Christer; Forslund, Pär; Höglund, Jacob

    1985-07-01

    To examine if differences in egg predation rates could explain differences in bird community composition, egg predation was studied in two years on small islands in a South Swedish lake and on the nearby mainland using both natural and artificial nests.In plots with similar vegetation, the combined density of ground- and tree-nesting bird species did not differ between the islands and the mainland. Egg predation rates were similar on islands and the mainland for natural Turdus nests in two years, and for artificial Turdus and Phylloscopus nests. Unmarked and unvisited experimental nests suffered similar rate of egg predation as marked and visited nests. Egg predation rates were higher on natural nests when artificial nests were also put out, increasing the total nest density. Initial egg predation rates in artificial nests were also higher than later when nest density had decreased by 75%.The egg predators involved differed for artificial Phylloscopus nests between the islands and the mainland. Small mammals were apparently responsible for 29% of the predation on the mainland, but none on the islands. Artificial Turdus nests near crow nests suffered from a higher egg predation rate than nests further away from crow nests. Daily survival rates of Turdus nests increased from the laying to the incubation and further to the fledging state.Egg predation can not explain differences in bird community composition between islands and mainland in the present case.

  11. Biogeographic variation in behavioral and morphological responses to predation risk.

    Science.gov (United States)

    Large, Scott I; Smee, Delbert L

    2013-04-01

    The expression of prey antipredator defenses is often related to ambient consumer pressure, and prey express greater defenses under intense consumer pressure. Predation is generally greater at lower latitudes, and antipredator defenses often display a biogeographic pattern. Predation pressure may also vary significantly between habitats within latitudes, making biogeographic patterns difficult to distinguish. Furthermore, invasive predators may also influence the expression of prey defenses in ecological time. The purpose of this study was to determine how these factors influence the strength of antipredator responses. To assess patterns in prey antipredator defenses based upon geographic range (north vs. south), habitat type (wave-protected vs. wave-exposed shores), and invasive predators, we examined how native rock (Cancer irroratus) and invasive green (Carcinus maenas) crab predators influence the behavioral and morphological defenses of dogwhelk (Nucella lapillus) prey from habitats that differ in wave exposure across an ~230 km range within the Gulf of Maine. The expression of behavioral and morphological antipredatory responses varied according to wave exposure, geographic location, and predator species. Dogwhelks from areas with an established history with green crabs exhibited the largest behavioral and morphological antipredator responses to green crabs. Dogwhelk behavioral responses to rock crabs did not vary between habitats or geographic regions, although morphological responses were greater further south where predation pressure was greatest. These findings suggest that dogwhelk responses to invasive and native predators vary according to geographic location and habitat, and are strongly affected by ambient predation pressure due to the invasion history of an exotic predator.

  12. Fatal Attraction? Intraguild Facilitation and Suppression among Predators.

    Science.gov (United States)

    Sivy, Kelly J; Pozzanghera, Casey B; Grace, James B; Prugh, Laura R

    2017-11-01

    Competition and suppression are recognized as dominant forces that structure predator communities. Facilitation via carrion provisioning, however, is a ubiquitous interaction among predators that could offset the strength of suppression. Understanding the relative importance of these positive and negative interactions is necessary to anticipate community-wide responses to apex predator declines and recoveries worldwide. Using state-sponsored wolf (Canis lupus) control in Alaska as a quasi experiment, we conducted snow track surveys of apex, meso-, and small predators to test for evidence of carnivore cascades (e.g., mesopredator release). We analyzed survey data using an integrative occupancy and structural equation modeling framework to quantify the strengths of hypothesized interaction pathways, and we evaluated fine-scale spatiotemporal responses of nonapex predators to wolf activity clusters identified from radio-collar data. Contrary to the carnivore cascade hypothesis, both meso- and small predator occupancy patterns indicated guild-wide, negative responses of nonapex predators to wolf abundance variations at the landscape scale. At the local scale, however, we observed a near guild-wide, positive response of nonapex predators to localized wolf activity. Local-scale association with apex predators due to scavenging could lead to landscape patterns of mesopredator suppression, suggesting a key link between occupancy patterns and the structure of predator communities at different spatial scales.

  13. Fatal attraction? Intraguild facilitation and suppression among predators

    Science.gov (United States)

    Sivy, Kelly J.; Pozzanghera, Casey B.; Grace, James B.; Prugh, Laura R.

    2017-01-01

    Competition and suppression are recognized as dominant forces that structure predator communities. Facilitation via carrion provisioning, however, is a ubiquitous interaction among predators that could offset the strength of suppression. Understanding the relative importance of these positive and negative interactions is necessary to anticipate community-wide responses to apex predator declines and recoveries worldwide. Using state-sponsored wolf (Canis lupus) control in Alaska as a quasi experiment, we conducted snow track surveys of apex, meso-, and small predators to test for evidence of carnivore cascades (e.g., mesopredator release). We analyzed survey data using an integrative occupancy and structural equation modeling framework to quantify the strengths of hypothesized interaction pathways, and we evaluated fine-scale spatiotemporal responses of nonapex predators to wolf activity clusters identified from radio-collar data. Contrary to the carnivore cascade hypothesis, both meso- and small predator occupancy patterns indicated guild-wide, negative responses of nonapex predators to wolf abundance variations at the landscape scale. At the local scale, however, we observed a near guild-wide, positive response of nonapex predators to localized wolf activity. Local-scale association with apex predators due to scavenging could lead to landscape patterns of mesopredator suppression, suggesting a key link between occupancy patterns and the structure of predator communities at different spatial scales.

  14. Predator cannibalism can intensify negative impacts on heterospecific prey.

    Science.gov (United States)

    Takatsu, Kunio; Kishida, Osamu

    2015-07-01

    Although natural populations consist of individuals with different traits, and the degree of phenotypic variation varies among populations, the impact of phenotypic variation on ecological interactions has received little attention, because traditional approaches to community ecology assume homogeneity of individuals within a population. Stage structure, which is a common way of generating size and developmental variation within predator populations, can drive cannibalistic interactions, which can affect the strength of predatory effects on the predator's heterospecific prey. Studies have shown that predator cannibalism weakens predatory effects on heterospecific prey by reducing the size of the predator population and by inducing less feeding activity of noncannibal predators. We predict, however, that predator cannibalism, by promoting rapid growth of the cannibals, can also intensify predation pressure on heterospecific prey, because large predators have large resource requirements and may utilize a wider variety of prey species. To test this hypothesis, we conducted an experiment in which we created carnivorous salamander (Hynobius retardatus) populations with different stage structures by manipulating the salamander's hatch timing (i.e., populations with large or small variation in the timing of hatching), and explored the resultant impacts on the abundance, behavior, morphology, and life history of the salamander's large heterospecific prey, Rana pirica frog tadpoles. Cannibalism was rare in salamander populations having small hatch-timing variation, but was frequent in those having large hatch-timing variation. Thus, giant salamander cannibals occurred only in the latter. We clearly showed that salamander giants exerted strong predation pressure on frog tadpoles, which induced large behavioral and morphological defenses in the tadpoles and caused them to metamorphose late at large size. Hence, predator cannibalism arising from large variation in the timing

  15. Taphonomy for taxonomists: Implications of predation in small mammal studies

    Science.gov (United States)

    Fernández-Jalvo, Yolanda; Andrews, Peter; Denys, Christiane; Sesé, Carmen; Stoetzel, Emmanuelle; Marin-Monfort, Dolores; Pesquero, Dolores

    2016-05-01

    Predation is one of the most recurrent sources of bone accumulations. The influence of predation is widely studied for large mammal sites where humans, acting as predators, produce bone accumulations similar to carnivore accumulations. Similarly, small mammal fossil sites are mainly occupation levels of predators (nests or dens). In both cases, investigations of past events can be compared with present day equivalents or proxies. Chewing marks are sometimes present on large mammal predator accumulations, but digestion traits are the most direct indication of predation, and evidence for this is always present in small mammal (prey) fossil assemblages. Digestion grades and frequency indicates predator type and this is well established since the publication of Andrews (1990). The identification of the predator provides invaluable information for accurate interpretation of the palaeoenvironment. Traditionally, palaeoenvironmental interpretations are obtained from the taxonomic species identified in the site, but rather than providing direct interpretations of the surrounding palaeoenvironment, this procedure actually describes the dietary preferences of the predators and the type of occupation (nests, marking territory, dens, etc). This paper reviews the identification of traits produced by predators on arvicolins, murins and soricids using a method that may be used equally by taxonomists and taphonomists. It aims to provide the "tools" for taxonomists to identify the predator based on their methodology, which is examining the occlusal surfaces of teeth rather than their lateral aspects. This will greatly benefit both the work of taphonomists and taxonomists to recognize signs of predation and the improvement of subsequent palaeoecological interpretations of past organisms and sites by identifying both the prey and the predator.

  16. Getting Started with Hibernate 3

    CERN Document Server

    Elliott, James

    2008-01-01

    Hibernate has clearly arrived. Are you ready to benefit from its simple way of working with relational databases as Java objects? This PDF updates the introductory material from the award-winning Hibernate: A Developer's Notebook to teach you how to jump right in and get productive with the current release of Hibernate. You'll be walked through the ins and outs of setting up Hibernate and some related tools that make it easier to use--and that may give you new ideas about how to store information in your Java programs. In short, this PDF gives you exactly the information you need to start u

  17. Getting started With Amazon Redshift

    CERN Document Server

    Bauer, Stefan

    2013-01-01

    Getting Started With Amazon Redshift is a step-by-step, practical guide to the world of Redshift. Learn to load, manage, and query data on Redshift.This book is for CIOs, enterprise architects, developers, and anyone else who needs to get familiar with RedShift. The CIO will gain an understanding of what their technical staff is working on; the technical implementation personnel will get an in-depth view of the technology, and what it will take to implement their own solutions.

  18. Cannibalistic Predator-Prey Model with Disease in Predator — A Delay Model

    Science.gov (United States)

    Biswas, Santosh; Samanta, Sudip; Chattopadhyay, Joydev

    In this paper, we propose and analyze a cannibalistic predator-prey model with a transmissible disease in the predator population. The disease can be transmitted through contacts with infected individuals as well as the cannibalism of an infected predator. We also consider incubation delay in disease transmission, where the incubation period represents the time in which the infectious agent develops in the host. Local stability analysis of the system around the biologically feasible equilibria is studied. Bifurcation analysis of the system around interior equilibrium is also studied. Applying the normal form theory and central manifold theorem, the direction of Hopf bifurcation, the stability and the period of bifurcating periodic solutions are derived. Under appropriate conditions, the permanence of the system with time delay is proved. Our results suggest that incubation delay destabilizes the system and can produce chaos. We also observe that cannibalism can control disease and population oscillations. Extensive numerical simulations are performed to support our analytical results.

  19. Predation on exotic zebra mussels by native fishes: Effects on predator and prey

    Science.gov (United States)

    Magoulick, D.D.; Lewis, L.C.

    2002-01-01

    1. Exotic zebra mussels, Dreissena polymorpha, occur in southern U.S. waterways in high densities, but little is known about the interaction between native fish predators and zebra mussels. Previous studies have suggested that exotic zebra mussels are low profitability prey items and native vertebrate predators are unlikely to reduce zebra mussel densities. We tested these hypotheses by observing prey use of fishes, determining energy content of primary prey species of fishes, and conducting predator exclusion experiments in Lake Dardanelle, Arkansas. 2. Zebra mussels were the primary prey eaten by 52.9% of blue catfish, Ictalurus furcatus; 48.2% of freshwater drum, Aplodinotus grunniens; and 100% of adult redear sunfish, Lepomis microlophus. Blue catfish showed distinct seasonal prey shifts, feeding on zebra mussels in summer and shad, Dorosoma spp., during winter. Energy content (joules g-1) of blue catfish prey (threadfin shad, Dorosoma petenense; gizzard shad, D. cepedianum; zebra mussels; and asiatic clams, Corbicula fluminea) showed a significant species by season interaction, but shad were always significantly greater in energy content than bivalves examined as either ash-free dry mass or whole organism dry mass. Fish predators significantly reduced densities of large zebra mussels (>5 mm length) colonising clay tiles in the summers of 1997 and 1998, but predation effects on small zebra mussels (???5 mm length) were less clear. 3. Freshwater drum and redear sunfish process bivalve prey by crushing shells and obtain low amounts of higher-energy food (only the flesh), whereas blue catfish lack a shell-crushing apparatus and ingest large amounts of low-energy food per unit time (bivalves with their shells). Blue catfish appeared to select the abundant zebra mussel over the more energetically rich shad during summer, then shifted to shad during winter when shad experienced temperature-dependent stress and mortality. Native fish predators can suppress adult zebra

  20. The start of the harvest

    CERN Multimedia

    2011-01-01

    The first major particle physics summer conference has just started this week in Grenoble. After the Quark-Matter conference, the Europhysics Conference on High-Energy Physics marks the start of a promising harvest for the LHC experiments.   For the first time, the collaborations will be presenting their latest results based on all luminosity taken until end of June, which will provide more precise measurements in many areas. Thanks to the excellent performance of the LHC, the experiments have already accumulated a substantial quantity of data allowing them to push back the known limits and refine measurements in many fields ranging from b physics to the search for the Higgs boson and for dark matter. At the time of writing, the LHC collaborations are about to present these new results in an energy range which has never previously been explored. I have congratulated all the teams involved in getting the LHC into operation in record time with great efficiency. Today I would like to acknowledge the...

  1. Rapid starting methanol reactor system

    Science.gov (United States)

    Chludzinski, Paul J.; Dantowitz, Philip; McElroy, James F.

    1984-01-01

    The invention relates to a methanol-to-hydrogen cracking reactor for use with a fuel cell vehicular power plant. The system is particularly designed for rapid start-up of the catalytic methanol cracking reactor after an extended shut-down period, i.e., after the vehicular fuel cell power plant has been inoperative overnight. Rapid system start-up is accomplished by a combination of direct and indirect heating of the cracking catalyst. Initially, liquid methanol is burned with a stoichiometric or slightly lean air mixture in the combustion chamber of the reactor assembly. The hot combustion gas travels down a flue gas chamber in heat exchange relationship with the catalytic cracking chamber transferring heat across the catalyst chamber wall to heat the catalyst indirectly. The combustion gas is then diverted back through the catalyst bed to heat the catalyst pellets directly. When the cracking reactor temperature reaches operating temperature, methanol combustion is stopped and a hot gas valve is switched to route the flue gas overboard, with methanol being fed directly to the catalytic cracking reactor. Thereafter, the burner operates on excess hydrogen from the fuel cells.

  2. Experimental predator removal causes rapid salt marsh die-off.

    Science.gov (United States)

    Bertness, Mark D; Brisson, Caitlin P; Coverdale, Tyler C; Bevil, Matt C; Crotty, Sinead M; Suglia, Elena R

    2014-07-01

    Salt marsh habitat loss to vegetation die-offs has accelerated throughout the western Atlantic in the last four decades. Recent studies have suggested that eutrophication, pollution and/or disease may contribute to the loss of marsh habitat. In light of recent evidence that predators are important determinants of marsh health in New England, we performed a total predator exclusion experiment. Here, we provide the first experimental evidence that predator depletion can cause salt marsh die-off by releasing the herbivorous crab Sesarma reticulatum from predator control. Excluding predators from a marsh ecosystem for a single growing season resulted in a >100% increase in herbivory and a >150% increase in unvegetated bare space compared to plots with predators. Our results confirm that marshes in this region face multiple, potentially synergistic threats. © 2014 The Authors. Ecology Letters published by John Wiley & Sons Ltd and CNRS.

  3. Forest fragmentation and avian nest predation in forested landscapes.

    Science.gov (United States)

    Small, M F; Hunter, M L

    1988-06-01

    The size of forest fragments, the use of land bordering fragments, and the distance of nests from an edge all affect the frequency of predation upon bird nests in Maine (USA), an area where the forest has been fragmented by roads, but not significantly reduced in area. We placed artificial nests containing quail eggs in forests of different sizes and at various distances from the edge to test which of these factors was most important in describing predation. Predation was greatest in small tracts surrounded completely by land. Large areas and those bordered on at least one side by a large water body had lower predation rates. This suggests that influx of predators from nearby habitats may be responsible for much of the nest predation in forest fragments.

  4. The risk of predation favors cooperation among breeding prey

    Science.gov (United States)

    Krama, Tatjana; Berzins, Arnis; Rantala, Markus J

    2010-01-01

    Empirical studies have shown that animals often focus on short-term benefits under conditions of predation risk, which reduces the likelihood that they will cooperate with others. However, some theoretical studies predict that animals in adverse conditions should not avoid cooperation with their neighbors since it may decrease individual risks and increase long-term benefits of reciprocal help. We experimentally tested these two alternatives to find out whether increased predation risk enhances or diminishes the occurrence of cooperation in mobbing, a common anti-predator behavior, among breeding pied flycatchers, Ficedula hypoleuca. Our results show that birds attended mobs initiated by their neighbors more often, approached the stuffed predator significantly more closely, and mobbed it at a higher intensity in areas where the perceived risk of predation was experimentally increased. This study demonstrates a positive impact of predation risk on cooperation in breeding songbirds, which might help to explain the emergence and evolution of cooperation. PMID:20714404

  5. Nest predation research: Recent findings and future perspectives

    Science.gov (United States)

    Chalfoun, Anna D.; Ibanez-Alamo, J. D.; Magrath, R. D.; Schmidt, Kenneth A.; Thomson, R. L.; Oteyza, Juan C.; Haff, T. M.; Martin, T.E.

    2016-01-01

    Nest predation is a key source of selection for birds that has attracted increasing attention from ornithologists. The inclusion of new concepts applicable to nest predation that stem from social information, eavesdropping or physiology has expanded our knowledge considerably. Recent methodological advancements now allow focus on all three players within nest predation interactions: adults, offspring and predators. Indeed, the study of nest predation now forms a vital part of avian research in several fields, including animal behaviour, population ecology, evolution and conservation biology. However, within nest predation research there are important aspects that require further development, such as the comparison between ecological and evolutionary antipredator responses, and the role of anthropogenic change. We hope this review of recent findings and the presentation of new research avenues will encourage researchers to study this important and interesting selective pressure, and ultimately will help us to better understand the biology of birds.

  6. The narrow range of perceived predation: a 19 group study

    Directory of Open Access Journals (Sweden)

    Olivier Mesly

    2013-05-01

    Full Text Available This paper rests largely on the works of Mesly (1999 to 2012. It argues that the phenomenon of perceived predation as a functional behavioural phenomenon is subjected to certain limits, a finding based on studies performed on 19 different groups spread over a four-year span. It also finds a constant of k = 1.3 which reflects the invariant nature of perceived predation. These findings add to the theory of financial predation which stipulates that financial predators operate below the limits of detection pertaining to their customers (and market regulators. They are experts at minimizing the perception that clients could have that they are after their money, causing them financial harm, by surprise (perceived predation. Understanding the narrow range in which financial predators operate is setting the grounds to offer better protection to investors and to implementing better control and punitive measures.

  7. Parasite and predator risk assessment: nuanced use of olfactory cues

    OpenAIRE

    Sharp, John G.; Garnick, Sarah; Mark A Elgar; Coulson, Graeme

    2015-01-01

    Foraging herbivores face twin threats of predation and parasite infection, but the risk of predation has received much more attention. We evaluated, experimentally, the role of olfactory cues in predator and parasite risk assessment on the foraging behaviour of a population of marked, free-ranging, red-necked wallabies (Macropus rufogriseus). The wallabies adjusted their behaviour according to these olfactory cues. They foraged less, were more vigilant and spent less time at feeders placed in...

  8. PREDATOR IDENTITY AND ADDITIVE EFFECTS IN A TREEHOLE COMMUNITY

    OpenAIRE

    GRISWOLD, MARCUS W.; Lounibos,L Philip

    2006-01-01

    Multiple predator species can interact as well as strongly affect lower trophic levels, resulting in complex, nonadditive effects on prey populations and community structure. Studies of aquatic systems have shown that interactive effects of predators on prey are not necessarily predictable from the direct effects of each species alone. To test for complex interactions, the individual and combined effects of a top and intermediate predator on larvae of native and invasive mosquito prey were ex...

  9. Effectiveness of predator odors as gray squirrel repellents

    OpenAIRE

    Rosell, Frank

    2001-01-01

    The ability of gray squirrels (Sciurus carolinensis) to discriminate between different predator odors and the use of predator odors to deter gray squirrels from foraging on plants have not been previously investigated. To test the hypothesis that predator scent decreases foraging, I investigated the effect of such scent on consumption of butternuts (Juglans cinerea) in the field. Results showed that (i) red fox (Vulpes vulpes) scent was significantly more effective than either a control or hu...

  10. Local and landscape drivers of predation services in urban gardens.

    Science.gov (United States)

    Philpott, Stacy M; Bichier, Peter

    2017-04-01

    In agroecosystems, local and landscape features, as well as natural enemy abundance and richness, are significant predictors of predation services that may result in biological control of pests. Despite the increasing importance of urban gardening for provisioning of food to urban populations, most urban gardeners suffer from high pest problems, and have little knowledge about how to manage their plots to increase biological control services. We examined the influence of local, garden scale (i.e., herbaceous and arboreal vegetation abundance and diversity, ground cover) and landscape (i.e., landscape diversity and surrounding land use types) characteristics on predation services provided by naturally occurring predators in 19 urban gardens in the California central coast. We introduced sentinel pests (moth eggs and larvae and pea aphids) onto greenhouse-raised plants taken to gardens and assigned to open or bagged (predator exclosure) treatments. We found high predation rates with between 40% and 90% of prey items removed in open treatments. Predation services varied with local and landscape factors, but significant predictors differed by prey species. Predation of eggs and aphids increased with vegetation complexity in gardens, but larvae predation declined with vegetation complexity. Smaller gardens experienced higher predation services, likely due to increases in predator abundance in smaller gardens. Several ground cover features influenced predation services. In contrast to patterns in rural agricultural landscapes, predation on aphids declined with increases in landscape diversity. In sum, we report the relationships between several local management factors, as well as landscape surroundings, and implications for garden management. © 2017 by the Ecological Society of America.

  11. Ingredients: where pet food starts.

    Science.gov (United States)

    Thompson, Angele

    2008-08-01

    Every clinician is asked "What should I feed my pet?" Understanding the ingredients in pet food is an important part of making the best recommendation. Pet food can be as simple as one ingredient or as complicated as containing more than 60 ingredients. Pet food and its ingredients are regulated by the Food and Drug Administration and state feed officials. Part of that regulation is the review and definition of ingredients. Existing ingredients change and new ingredients become available so the need for ingredient definitions grows. Ingredients for product formulations are chosen based on their nutrient content, digestibility, palatability, functionality, availability, and cost. As an example, a typical, nutritionally complete dry dog food with 42 ingredients is examined and the ingredients are discussed here. Safe, healthy pet food starts with safe ingredients sourced from well-monitored suppliers. The ultimate goal of both veterinarians and pet food manufacturers is the same--long healthy lives for dogs and cats.

  12. Personality-dependent dispersal cancelled under predation risk

    National Research Council Canada - National Science Library

    Cote, Julien; Fogarty, Sean; Tymen, Blaise; Sih, Andrew; Brodin, Tomas

    2013-01-01

    .... Here, we used mosquitofish (Gambusia affinis) to test whether personality-dependent dispersal varies with predation risk, a factor that should induce boldness or sociability-dependent dispersal...

  13. Ecosystem context and historical contingency in apex predator recoveries

    Science.gov (United States)

    Stier, Adrian C.; Samhouri, Jameal F.; Novak, Mark; Marshall, Kristin N.; Ward, Eric J.; Holt, Robert D.; Levin, Phillip S.

    2016-01-01

    Habitat loss, overexploitation, and numerous other stressors have caused global declines in apex predators. This “trophic downgrading” has generated widespread concern because of the fundamental role that apex predators can play in ecosystem functioning, disease regulation, and biodiversity maintenance. In attempts to combat declines, managers have conducted reintroductions, imposed stricter harvest regulations, and implemented protected areas. We suggest that full recovery of viable apex predator populations is currently the exception rather than the rule. We argue that, in addition to well-known considerations, such as continued exploitation and slow life histories, there are several underappreciated factors that complicate predator recoveries. These factors include three challenges. First, a priori identification of the suite of trophic interactions, such as resource limitation and competition that will influence recovery can be difficult. Second, defining and accomplishing predator recovery in the context of a dynamic ecosystem requires an appreciation of the timing of recovery, which can determine the relative density of apex predators and other predators and therefore affect competitive outcomes. Third, successful recovery programs require designing adaptive sequences of management strategies that embrace key environmental and species interactions as they emerge. Consideration of recent research on food web modules, alternative stable states, and community assembly offer important insights for predator recovery efforts and restoration ecology more generally. Foremost among these is the importance of a social-ecological perspective in facilitating a long-lasting predator restoration while avoiding unintended consequences. PMID:27386535

  14. Predators are attracted to the olfactory signals of prey.

    Directory of Open Access Journals (Sweden)

    Nelika K Hughes

    2010-09-01

    Full Text Available Predator attraction to prey social signals can force prey to trade-off the social imperatives to communicate against the profound effect of predation on their future fitness. These tradeoffs underlie theories on the design and evolution of conspecific signalling systems and have received much attention in visual and acoustic signalling modes. Yet while most territorial mammals communicate using olfactory signals and olfactory hunting is widespread in predators, evidence for the attraction of predators to prey olfactory signals under field conditions is lacking.To redress this fundamental issue, we examined the attraction of free-roaming predators to discrete patches of scents collected from groups of two and six adult, male house mice, Mus domesticus, which primarily communicate through olfaction. Olfactorily-hunting predators were rapidly attracted to mouse scent signals, visiting mouse scented locations sooner, and in greater number, than control locations. There were no effects of signal concentration on predator attraction to their prey's signals.This implies that communication will be costly if conspecific receivers and eavesdropping predators are simultaneously attracted to a signal. Significantly, our results also suggest that receivers may be at greater risk of predation when communicating than signallers, as receivers must visit risky patches of scent to perform their half of the communication equation, while signallers need not.

  15. Assessing predation risk: optimal behaviour and rules of thumb.

    Science.gov (United States)

    Welton, Nicky J; McNamara, John M; Houston, Alasdair I

    2003-12-01

    We look at a simple model in which an animal makes behavioural decisions over time in an environment in which all parameters are known to the animal except predation risk. In the model there is a trade-off between gaining information about predation risk and anti-predator behaviour. All predator attacks lead to death for the prey, so that the prey learns about predation risk by virtue of the fact that it is still alive. We show that it is not usually optimal to behave as if the current unbiased estimate of the predation risk is its true value. We consider two different ways to model reproduction; in the first scenario the animal reproduces throughout its life until it dies, and in the second scenario expected reproductive success depends on the level of energy reserves the animal has gained by some point in time. For both of these scenarios we find results on the form of the optimal strategy and give numerical examples which compare optimal behaviour with behaviour under simple rules of thumb. The numerical examples suggest that the value of the optimal strategy over the rules of thumb is greatest when there is little current information about predation risk, learning is not too costly in terms of predation, and it is energetically advantageous to learn about predation. We find that for the model and parameters investigated, a very simple rule of thumb such as 'use the best constant control' performs well.

  16. Adaptive aggregation by spider mites under predation risk.

    Science.gov (United States)

    Dittmann, Lena; Schausberger, Peter

    2017-09-06

    Grouping together is a commonly observed anti-predator strategy. Possible anti-predator benefits of aggregation include the encounter/avoidance effect for visually hunting predators and the dilution effect, together dubbed attack abatement. Possible costs opposing the dilution effect are easier detection of aggregated than scattered individuals. The benefits of attack abatement, and opposing costs after group detection, are poorly understood for chemosensory predator-prey interactions. We tackled this issue by assessing the aggregation behavior of spider mites Tetranychus urticae under predation risk emanating from predatory mites Phytoseiulus persimilis. We examined whether adult spider mite females aggregate more tightly when perceiving predator cues (traces left and eggs), representing graded risk levels, and whether grouping enhances survival in physical predator presence. The spider mites aggregated more tightly and were more active in presence than absence of predator cues. Grouped spider mites were less likely and later detected and attacked than scattered spider mites. Moreover, encounter and attack of one group member did not increase the risk of other members to be attacked, as compared to scattered spider mites. To the best of our knowledge, our study is the first rigorous documentation of the adaptive benefit of tightened prey aggregation towards a purely chemosensorily hunting predator.

  17. Gregarious nesting - An anti-predator response in laying hens

    DEFF Research Database (Denmark)

    Riber, Anja Brinch

    2012-01-01

    in nesting strategy. The aim of the present experiment was to investigate whether gregarious nesting due to behavioural flexibility in nesting strategy is an anti-predator response. Twelve groups of 14–15 Isa Warren hens age 44 weeks were housed in pens each containing three adjacent roll-out nest boxes....... Nesting and spacing behaviour were video recorded for 5 days in each of three distinct periods; (a) pre-predator; a pre-exposure period, (b) predator; a period with daily exposure to a simulated attack by a lifelike flying model of a hooded crow (Corvus cornix, a potential egg-predator), and (c) post...

  18. Cumulative human impacts on marine predators

    DEFF Research Database (Denmark)

    Maxwell, Sara M; Hazen, Elliott L; Bograd, Steven J

    2013-01-01

    Sanctuaries. High variation in underlying species and cumulative impact distributions means that neither alone is sufficient for effective spatial management. Instead, comprehensive management approaches accounting for both cumulative human impacts and trade-offs among multiple stressors must be applied......Stressors associated with human activities interact in complex ways to affect marine ecosystems, yet we lack spatially explicit assessments of cumulative impacts on ecologically and economically key components such as marine predators. Here we develop a metric of cumulative utilization and impact...... in planning the use of marine resources....

  19. Risk communication in sexually violent predator hearings.

    Science.gov (United States)

    Scott, Sarah; Gilcrist, Brett; Thurston, Nicole; Huss, Matthew T

    2010-01-01

    Sexually violent predator (SVP) laws use the civil commitment process to confine mentally disordered and dangerous offenders who are at high risk to reoffend. Few studies have examined how jurors decide SVP cases. As a result, a pilot study and three experimental studies were conducted, in which victim type, risk communication, and juror education were manipulated to assess juror response. Results continually illustrated that victim type was the most salient manipulation across studies and that the manner of risk communication and juror education had little impact on jurors. 2009 John Wiley & Sons, Ltd.

  20. Invasive toads shift predator-prey densities in animal communities by removing top predators.

    Science.gov (United States)

    Doody, J Sean; Soanes, Rebekah; Castellano, Christina M; Rhind, David; Green, Brian; McHenry, Colin R; Clulow, Simon

    2015-09-01

    Although invasive species can have substantial impacts on animal communities, cases of invasive species facilitating native species by removing their predators have rarely been demonstrated across vertebrate trophic linkages. The predictable spread of the invasive cane toad (Rhinella marina), however, offered a unique opportunity to quantify cascading effects. In northern Australia, three species of predatory monitor lizards suffered severe population declines due to toad-induced lethal toxic ingestion (yellow-spotted monitor (Varanus panoptes), Mertens' water monitor (V. mertensi), Mitchell's water monitor (V. mitchelli). We, thus, predicted subsequent increases in the abundance and recruitment of prey species due to the reduction of those predators. Toad-induced population-level declines in the water monitor species approached 50% over a five-year period spanning the toad invasion, apparently causing fledging success of the Crimson Finch (Neochmia.phaeton) to increase from 55% to 81%. The consensus of our original and published long-term data is that invasive cane toads are causing predators to lose a foothold on top-down regulation of their prey, triggering shifts in the relative densities of predator and prey in the Australian tropical savannah ecosystem.

  1. Predation pressure by avian predators suggests summer limitation of small-mammal populations in the Canadian Arctic.

    Science.gov (United States)

    Therrien, J F; Gauthier, G; Korpimäki, E; Bêty, J

    2014-01-01

    Predation has been suggested to be especially important in simple food webs and less productive ecosystems such as the arctic tundra, but very few data are available to evaluate this hypothesis. We examined the hypothesis that avian predators could drive the population dynamics of two cyclic lemming species in the Canadian Arctic. A dense and diverse suite of predatory birds, including the Snowy Owl (Bubo scandiacus), the Rough-legged Hawk (Buteo lagopus), and the Long-tailed Jaeger (Stercorarius longicaudus), inhabits the arctic tundra and prey on collared (Dicrostonyx groenlandicus) and brown (Lemmus trimucronatus) lemmings during the snow-free period. We evaluated the predation pressure exerted by these predators by combining their numerical (variation in breeding and fledgling numbers) and functional (variation in diet and daily consumption rates) responses to variations in lemming densities over the 2004-2010 period. Breeding density and number of fledglings produced by the three main avian predators increased sharply without delay in response to increasing lemming densities. The proportion of collared lemmings in the diet of those predators was high at low lemming density (both species) but decreased as lemming density increased. However, we found little evidence that their daily consumption rates vary in relation to changes in lemming density. Total consumption rate by avian predators initially increased more rapidly for collared lemming but eventually leveled off at a much higher value for brown lemmings, the most abundant species at our site. The combined daily predation rate of avian predators exceeded the maximum daily potential growth rates of both lemming species except at the highest recorded densities for brown lemmings. We thus show, for the first time, that predation pressure exerted without delay by avian predators can limit populations of coexisting lemming species during the snow-free period, and thus, that predation could play a role in the

  2. Parental investment decisions in response to ambient nest-predation risk versus actual predation on the prior nest

    Science.gov (United States)

    Chalfoun, A.D.; Martin, T.E.

    2010-01-01

    Theory predicts that parents should invest less in dependent offspring with lower reproductive value, such as those with a high risk of predation. Moreover, high predation risk can favor reduced parental activity when such activity attracts nest predators. Yet, the ability of parents to assess ambient nest-predation risk and respond adaptively remains unclear, especially where nest-predator assemblages are diverse and potentially difficult to assess. We tested whether variation in parental investment by a multi-brooded songbird (Brewer's Sparrow, Spizella breweri) in an environment (sagebrush steppe) with diverse predators was predicted by ambient nest-predation risk or direct experience with nest predation. Variation among eight sites in ambient nest-predation risk, assayed by daily probabilities of nest predation, was largely uncorrelated across four years. In this system risk may therefore be unpredictable, and aspects of parental investment (clutch size, egg mass, incubation rhythms, nestling-feeding rates) were not related to ambient risk. Moreover, investment at first nests that were successful did not differ from that at nests that were depredated, suggesting parents could not assess and respond to territorylevel nest-predation risk. However, parents whose nests were depredated reduced clutch sizes and activity at nests attempted later in the season by increasing the length of incubation shifts (on-bouts) and recesses (off-bouts) and decreasing trips to feed nestlings. In this unpredictable environment parent birds may therefore lack sufficient cues of ambient risk on which to base their investment decisions and instead rely on direct experience with nest predation to inform at least some of their decisions. ?? 2010 The Cooper Ornithological Society.

  3. Predators on private land: broad-scale socioeconomic interactions influence large predator management

    Directory of Open Access Journals (Sweden)

    Hayley S. Clements

    2016-06-01

    Full Text Available The proliferation of private land conservation areas (PLCAs is placing increasing pressure on conservation authorities to effectively regulate their ecological management. Many PLCAs depend on tourism for income, and charismatic large mammal species are considered important for attracting international visitors. Broad-scale socioeconomic factors therefore have the potential to drive fine-scale ecological management, creating a systemic scale mismatch that can reduce long-term sustainability in cases where economic and conservation objectives are not perfectly aligned. We assessed the socioeconomic drivers and outcomes of large predator management on 71 PLCAs in South Africa. Owners of PLCAs that are stocking free-roaming large predators identified revenue generation as influencing most or all of their management decisions, and rated profit generation as a more important objective than did the owners of PLCAs that did not stock large predators. Ecotourism revenue increased with increasing lion (Panthera leo density, which created a potential economic incentive for stocking lion at high densities. Despite this potential mismatch between economic and ecological objectives, lion densities were sustainable relative to available prey. Regional-scale policy guidelines for free-roaming lion management were ecologically sound. By contrast, policy guidelines underestimated the area required to sustain cheetah (Acinonyx jubatus, which occurred at unsustainable densities relative to available prey. Evidence of predator overstocking included predator diet supplementation and frequent reintroduction of game. We conclude that effective facilitation of conservation on private land requires consideration of the strong and not necessarily beneficial multiscale socioeconomic factors that influence private land management.

  4. Fish ladders: safe fish passage or hotspot for predation?

    Directory of Open Access Journals (Sweden)

    Angelo Antonio Agostinho

    Full Text Available Fish ladders are a strategy for conserving biodiversity, as they can provide connectivity between fragmented habitats and reduce predation on shoals that accumulate immediately below dams. Although the impact of predation downstream of reservoirs has been investigated, especially in juvenile salmonids during their downstream movements, nothing is known about predation on Neotropical fish in the attraction and containment areas commonly found in translocation facilities. This study analysed predation in a fish passage system at the Lajeado Dam on the Tocantins River in Brazil. The abundance, distribution, and the permanence (time spent of large predatory fish along the ladder, the injuries imposed by piranhas during passage and the presence of other vertebrate predators were investigated. From December 2002 to October 2003, sampling was conducted in four regions (downstream, along the ladder, in the forebay, and upstream of the reservoir using gillnets, cast nets and counts or visual observations. The captured fish were tagged with thread and beads, and any mutilations were registered. Fish, birds and dolphins were the main predator groups observed, with a predominance of the first two groups. The entrance to the ladder, in the downstream region, was the area with the highest number of large predators and was the only region with relevant non-fish vertebrates. The main predatory fish species were Rhaphiodon vulpinus, Hydrolycus armatus, and Serrasalmus rhombeus. Tagged individuals were detected predating along the ladder for up to 90 days. Mutilations caused by Serrasalmus attacks were noted in 36% of species and 4% of individuals at the top of the ladder. Our results suggested that the high density of fish in the restricted ladder environment, which is associated with injuries suffered along the ladder course and the presence of multiple predator groups with different predation strategies, transformed the fish corridor into a hotspot for

  5. Start and the restriction point.

    Science.gov (United States)

    Johnson, Amy; Skotheim, Jan M

    2013-12-01

    Commitment to division requires that cells sense, interpret, and respond appropriately to multiple signals. In most eukaryotes, cells commit to division in G1 before DNA replication. Beyond a point, known as Start in yeast and the restriction point in mammals, cells will proceed through the cell cycle despite changes in upstream signals. In metazoans, misregulated G1 control can lead to developmental problems or disease, so it is important to understand how cells decipher the myriad external and internal signals that contribute to the fundamental all-or-none decision to divide. Extensive study of G1 control in the budding yeast Saccharomyces cerevisiae and mammalian culture systems has revealed highly similar networks regulating commitment. However, protein sequences of functional orthologs often indicate a total lack of conservation suggesting significant evolution of G1 control. Here, we review recent studies defining the conserved and diverged features of G1 control and highlight systems-level aspects that may be common to other biological regulatory networks. Copyright © 2013 Elsevier Ltd. All rights reserved.

  6. Predators and predation rates of skylark Alauda arvensis and woodlark Lullula arborea nests in a semi-natural area in the Netherlands

    NARCIS (Netherlands)

    Praus, Libor; Hegemann, Arne; Tieleman, B. Irene; Weidinger, Karel

    2014-01-01

    Predation is a major cause of breeding failure in bird species with open nests. Although many studies have investigated nest predation rates, direct identification of nest predators is sporadic, especially in (semi-)natural habitats. We quantified nest success and identified nest predators in a

  7. Size-specific predation on marine invertebrate larvae.

    Science.gov (United States)

    Allen, Jonathan D

    2008-02-01

    Predation on planktonic larval stages is frequently a major source of mortality for the offspring of benthic marine invertebrates. Mortality rate likely varies with larval size and developmental stage, but few experiments have measured how these factors affect predation rates. I used experimental reductions in egg size to test how variation in larval size affects the likelihood of predation during planktonic development. Blastomeres of the sand dollar Dendraster excentricus were separated at the two-cell stage to produce half-sized zygotes. Larvae resulting from this manipulation were tested for their susceptibility to predation relative to whole-sized siblings at four ages. Individuals from each size class were simultaneously presented as prey items to five predators (crab zoeae, crab megalopae, chaetognaths, solitary tunicates, and postlarval fish) in the laboratory. Four predators consumed significantly more half-sized larvae than whole-sized larvae, but one predator type (postlarval fish) consumed more whole-sized larvae. Predators that consumed more half-sized larvae also preferentially consumed younger larvae. In contrast, postlarval fish showed no significant prey preference based on larval age. These results suggest that assumptions of constant mortality rates during development should be modified to account for the effects of larval size and age.

  8. Alarm calls of Bronze Mannikins communicate predator size to ...

    African Journals Online (AJOL)

    These groups were exposed to latex terrestrial snakes and mounted aerial raptors, and their alarm calls and predator response behaviours recorded. The Bronze Mannikins were able to discriminate between predators of different sizes, and increased their calling rate and decreased the end frequency of the alarm call in ...

  9. Toward understanding the effect of top predators on ecosystems

    Science.gov (United States)

    Lecomte, Nicolas; Ehrich, Dorothée; Ims, Rolf A

    2009-01-01

    To what extent top predators - carnivores at the top of food chains - drive or just respond to ecosystem dynamics is a central, but partially unresolved, question in ecology. In this report, we highlight how different research approaches employed in aquatic and terrestrial ecology may have a bearing on how the role of top predators in ecosystems is perceived. PMID:20948660

  10. Factors influencing predation associated with visits to artificial goose nests

    Science.gov (United States)

    Vacca, M. Michele; Handel, Colleen M.

    1988-01-01

    Artificial goose nests were used to determine what factors might increase predation after visits to nests of Cackling Canada Geese (Branta canadensis minima). We tested whether leaving the nest uncovered, marking the nest location with a flag, or placing the nest on an island or peninsula would increase the rate of predation. Predators destroyed significantly more of the nests with eggs exposed to view (61%) than of the nests with eggs covered with goose down (35%) (P nests located on peninsulas than on islands and equal proportions of flagged and unflagged nests were destroyed. We also determined that investigators attracted predators to the study area and caused an increase in predation at uncovered nests immediately after the visit. Covering the eggs with down essentially negated the effect of attracting predators when visiting the nest. Among the 46 nests destroyed, 78% were destroyed by birds and 22% by mammals. Results of our study suggested that visibility of exposed eggs rather than nest markers provided important cues to avian predators and that islands probably provided some refuge from mammalian predators. Investigators can take steps to minimize their impact on nesting success and should incorporate a measure of that impact in their studies.

  11. Geographic variation in avian clutch size and nest predation risk ...

    African Journals Online (AJOL)

    Geographic variation in avian clutch size is thought to be related to the variation in nest predation rate and food availability. We studied predation on artificial ground nests along a large-scale geographic gradient in South Africa characterised by increasing productivity from the deserts in the west to humid savannas in the ...

  12. Predation on artificial, solitary and aggregated wader nests on farmland.

    Science.gov (United States)

    Berg, Åke

    1996-08-01

    Predation rates on artificial wader nests, solitary curlew (Numenius arquata) and lapwing (Vanellus vanellus) nests and lapwing nests in colonies were studied on a farmland site in central Sweden. Predation rates were highest on artificial wader nests, intermediate on solitary curlew and lapwing nests and lowest on lapwing nests in colonies, probably because of active defence of adults at real nests and/or because of selection of nest sites with lower predation risk by breeding birds. A comparison of nests close to (≤50 m) and far away from (≥200 m) forest edges revealed no increased predation risk close to edges for any of the studied nest types. Predation risk changed during the season for artificial nests (highest in the middle of May), while predation rates on lapwing and curlew nests were more stable. Artificial nests seem to be inappropriate for measuring actual predation rates and temporal differences in predation rates on real nests, but they might be suitable for use as an index of spatial differences.

  13. Maternally induced intraclutch cannibalism: an adaptive response to predation risk?

    Science.gov (United States)

    Tigreros, Natasha; Norris, Rachel H; Wang, Eugenia H; Thaler, Jennifer S

    2017-04-01

    Theory on condition-dependent risk-taking indicates that when prey are in poor condition, their anti-predator responses should be weak. However, variation in responses resulting from differences in condition is generally considered an incidental by-product of organisms living in a heterogeneous environment. Using Leptinotarsa decemlineata beetles and stinkbug (Podisus maculiventris) predators, we hypothesised that in response to predation risk, parents improve larval nutritional condition and expression of anti-predator responses by promoting intraclutch cannibalism. We showed that mothers experiencing predation risk increase production of unviable trophic eggs, which assures provisioning of an egg meal to the newly hatched offspring. Next, we experimentally demonstrated that egg cannibalism reduces L. decemlineata vulnerability to predation by improving larval nutritional condition and expression of anti-predator responses. Intraclutch cannibalism in herbivorous insects might be a ubiquitous strategy, aimed to overcome the dual challenge of feeding on protein-limited diets while living under constant predation threat. © 2017 John Wiley & Sons Ltd/CNRS.

  14. Predation on large mammals in the Kafue National Park, Zambia

    African Journals Online (AJOL)

    The specimens were labelled for locality, date and predator. Only fresh kills were recorded; predators of older kills could not be identified. Where p()ssible a condition rating was made on the femur marrow of the kill, as described by Riney (1954). The age of prey specimens was determined by examination of the teeth.

  15. First observations of attempted nudibranch predation by sea anemones

    OpenAIRE

    Meij, van der, T.; Reijnen, B.T.

    2011-01-01

    On two separate occasions during fieldwork in Semporna (eastern Sabah, Malaysia), sea anemones of the family Edwardsiidae were observed attempting to feed on the nudibranch species Nembrotha lineolata and Phyllidia ocellata. These are the first in situ observations of nudibranch predation by sea anemones. This new record is compared with known information on sea slug predators.

  16. Phenotypic plasticity of planktonic rotifers as a response to predator.

    OpenAIRE

    VAJDIAKOVÁ, Nikola

    2014-01-01

    The aim of this thesis is to assemble essential information about phenotypic plasticity of zooplankton, especially planktonic rotifers. More specifically, the thesis is focused on predator­induced morphological changes. I introduced different types of predators and their behavioral, physiological and morphological impacts on zooplankton. Moreover, I examined the effects of inducible morphological defences on the planctic rotifers.

  17. Deep-ocean predation by a high Arctic cetacean

    DEFF Research Database (Denmark)

    Laidre, K.L.; Heide-Jørgensen, M.P.; Jørgensen, Ole A

    2004-01-01

    were correlated with predicted whale predation levels based on diving behavior. The difference in Greenland halibut biomass between an area with high predation and a comparable area without whales, approximately 19000 tonnes, corresponded well with the predicted biomass removed by the narwhal sub...

  18. The influence of nestling predation on nest site selection and ...

    African Journals Online (AJOL)

    Appropriate nest site selection and the response of parents and nestlings to intruders near the nest, are behaviours that could be adaptive in a species that is prone to nestling predation. This study showed that predation of bateleur nestlings in the Kruger National Park was high, that behaviour of adults and nestlings ...

  19. Simulating predator attacks on schools : Evolving composite tactics

    NARCIS (Netherlands)

    Demsar, Jure; Hemelrijk, Charlotte K.; Hildenbrandt, Hanno; Bajec, Iztok Lebar

    2015-01-01

    One hypothesis about the origins and evolution of coordinated animal movements is that they may serve as a defensive mechanism against predation. Earlier studies of the possible evolution of coordinated movement in prey concentrated on predators with simple attack tactics. Numerous studies, however,

  20. Assessing predation risk to threatened fauna from their prevalence in predator scats: dingoes and rodents in arid Australia.

    Directory of Open Access Journals (Sweden)

    Benjamin L Allen

    Full Text Available The prevalence of threatened species in predator scats has often been used to gauge the risks that predators pose to threatened species, with the infrequent occurrence of a given species often considered indicative of negligible predation risks. In this study, data from 4087 dingo (Canis lupus dingo and hybrids scats were assessed alongside additional information on predator and prey distribution, dingo control effort and predation rates to evaluate whether or not the observed frequency of threatened species in dingo scats warrants more detailed investigation of dingo predation risks to them. Three small rodents (dusky hopping-mice Notomys fuscus; fawn hopping-mice Notomys cervinus; plains mice Pseudomys australis were the only threatened species detected in <8% of dingo scats from any given site, suggesting that dingoes might not threaten them. However, consideration of dingo control effort revealed that plains mice distribution has largely retracted to the area where dingoes have been most heavily subjected to lethal control. Assessing the hypothetical predation rates of dingoes on dusky hopping-mice revealed that dingo predation alone has the potential to depopulate local hopping-mice populations within a few months. It was concluded that the occurrence of a given prey species in predator scats may be indicative of what the predator ate under the prevailing conditions, but in isolation, such data can have a poor ability to inform predation risk assessments. Some populations of threatened fauna assumed to derive a benefit from the presence of dingoes may instead be susceptible to dingo-induced declines under certain conditions.

  1. A predation cost to bold fish in the wild

    DEFF Research Database (Denmark)

    Hulthén, Kaj; Chapman, Ben; Nilsson, Anders P.

    2017-01-01

    is challenging and there is currently little data from the wild. We assayed individual behaviour and electronically tagged hundreds of fish (roach, Rutilus rutilus) before releasing them into their lake of origin, thereby exposing them to predation risk from avian apex predators (cormorants, Phalacrocorax carbo......Studies of predator-mediated selection on behaviour are critical for our understanding of the evolution and maintenance of behavioural diversity in natural populations. Consistent individual differences in prey behaviour, especially in the propensity to take risks ("boldness"), are widespread...... in the animal kingdom. Theory predicts that individual behavioural types differ in a cost-benefit trade-off where bolder individuals benefit from greater access to resources while paying higher predation-risk costs. However, explicitly linking predation events to individual behaviour under natural conditions...

  2. Exploratory behaviour and novel predator recognition: behavioural correlations across contexts.

    Science.gov (United States)

    Blake, C A; Gabor, C R

    2016-08-01

    It was hypothesized that the exploratory behaviour of an individual measured in a novel environment could predict its behaviour in response to a novel predator. This study examined novel predator recognition in the western mosquitofish Gambusia affinis, a species with individual differences in risk-taking, activity and exploration in novel environments. Prey responded with characteristic shoaling and avoidance in response to native predators, but did not show characteristic antipredator behaviour towards novel predators. Furthermore, G. affinis exhibited individual-level behavioural correlations across contexts but only when prey were tested with native predators. This could be the result of native predatory selection on behavioural correlations in the prey species. © 2016 The Fisheries Society of the British Isles.

  3. Modelling foraging movements of diving predators: a theoretical study exploring the effect of heterogeneous landscapes on foraging efficiency.

    Science.gov (United States)

    Chimienti, Marianna; Bartoń, Kamil A; Scott, Beth E; Travis, Justin M J

    2014-01-01

    starting point to understand the energetic reasons for a range of potential predator responses to spatial heterogeneity and environmental uncertainties in terms of search behaviour and predator-prey interactions. We highlight future directions that integrated empirical and modelling studies should take to improve our ability to predict how diving predators will be impacted by the deployment of manmade structures in the marine environment.

  4. Preschool Facilities - MDC_HeadStart

    Data.gov (United States)

    NSGIC Local Govt | GIS Inventory — A label (point) feature class of Head Start / Early Head Start/ Delegate Agencies/ Child Care Partnership & Family Day Care Homes Programs location in Miami-Dade...

  5. Diapause incidence in the two-spotted spider mite increases due to predator presence, not due to selective predation.

    NARCIS (Netherlands)

    Kroon, A.; Veenendaal, R.L.; Egas, C.J.M.; Bruin, J.; Sabelis, M.W.

    2005-01-01

    We recently reported evidence for increased diapause incidence in the spider mite Tetranychus urticae in the presence of the predatory mite Typhlodromus pyri. This effect may arise from (1) selective predation on non-diapause spider mites, (2) predator-induced diapause in spider mites, or (3) both.

  6. Predation of Small Eggs in Artificial Nests: Effects of Nest Position, Edge, and Potential Predator Abundance in Extensive Forest

    Science.gov (United States)

    Richard M. DeGraaf; Thomas J. Maier; Todd K. Fuller

    1999-01-01

    After photographtc observations in the field and laboratory tests indicated that small rodents might be significant predators on small eggs, we conducted a field study in central Massachusetts to compare predation of House Sparrow (Passer domesticus) eggs in artificial nests near to (5-15 m) and far from (100-120 m) forest edges and between ground...

  7. Vertebrate predators have minimal cascading effects on plant production or seed predation in an intact grassland ecosystem

    Science.gov (United States)

    John L. Maron; Dean E. Pearson

    2011-01-01

    The strength of trophic cascades in terrestrial habitats has been the subject of considerable interest and debate. We conducted an 8-year experiment to determine how exclusion of vertebrate predators, ungulates alone (to control for ungulate exclusion from predator exclusion plots) or none of these animals influenced how strongly a three-species assemblage of rodent...

  8. Frequency, efficiency, and physical characteristics of predation by generalist predators of brown marmorated stink bug (Hemiptera: Pentatomidae) eggs

    Science.gov (United States)

    The native generalist predator community of Halyomorpha halys, an invasive species in the United States and Europe, remains poorly studied. The aims of the current study were to determine which generalist predators that are commonly found in mid-Atlantic orchards and vegetable crops are capable of ...

  9. Do Predators Always Win? Starfish versus Limpets: A Hands-On Activity Examining Predator-Prey Interactions

    Science.gov (United States)

    Faria, Claudia; Boaventura, Diana; Galvao, Cecilia; Chagas, Isabel

    2011-01-01

    In this article we propose a hands-on experimental activity about predator-prey interactions that can be performed both in a research laboratory and in the classroom. The activity, which engages students in a real scientific experiment, can be explored not only to improve students' understanding about the diversity of anti-predator behaviors but…

  10. Teaching iSTART to Understand Spanish

    Science.gov (United States)

    Dascalu, Mihai; Jacovina, Matthew E.; Soto, Christian M.; Allen, Laura K.; Dai, Jianmin; Guerrero, Tricia A.; McNamara, Danielle S.

    2017-01-01

    iSTART is a web-based reading comprehension tutor. A recent translation of iSTART from English to Spanish has made the system available to a new audience. In this paper, we outline several challenges that arose during the development process, specifically focusing on the algorithms that drive the feedback. Several iSTART activities encourage…

  11. What Happens at the Lesson Start?

    Science.gov (United States)

    Saloviita, Timo

    2016-01-01

    Transitional periods, such as lesson starts, are necessary steps from one activity to another, but they also compete with time for actual learning. The aim of the present study was to replicate a previous pilot study on lesson starts and explore possible disturbances. In total, 130 lesson starts in Finnish basic education in grades 1-9 were…

  12. Active predation by Greenland shark Somniosus microcephalus

    DEFF Research Database (Denmark)

    Nielsen, Julius; hedeholm, Rasmus; Simon, Malene

    2013-01-01

    Dansk Havforskermøde 2013 Julius Nielsen, Rasmus Hedeholm, Malene Simon og John Fleng Steffensen The Greenland shark is ubiquitous in the northern part of the North Atlantic ranging from eastern Canada to northwest Russia . Although knowledge is scarce it is believed to be abundant and potentially...... important part of the ecosystem. Whether Greenland sharks in general should be considered opportunistic scavengers or active predators is therefore important in understanding ecosystem dynamics. Due to its sluggish appearance and a maximum reported swimming speed of 74 cm per second scavenging seems...... the most likely feeding strategy. However, recent studies suggest that Greenland sharks in some areas feed actively upon seals . Feeding ecology is poorly described in Greenland waters. In this study we provide information on feeding habits of 29 sharks caught in Greenland waters in the summer 2012...

  13. Plant species composition alters the sign and strength of an emergent multi-predator effect by modifying predator foraging behaviour.

    Directory of Open Access Journals (Sweden)

    Andrew Wilby

    Full Text Available The prediction of pest-control functioning by multi-predator communities is hindered by the non-additive nature of species functioning. Such non-additivity, commonly termed an emergent multi-predator effect, is known to be affected by elements of the ecological context, such as the structure and composition of vegetation, in addition to the traits of the predators themselves. Here we report mesocosm experiments designed to test the influence of plant density and species composition (wheat monoculture or wheat and faba bean polyculture on the emergence of multi-predator effects between Adalia bipunctata and Chrysoperla carnea, in their suppression of populations of the aphid Metopolophium dirhodum. The mesocosm experiments were followed by a series of behavioural observations designed to identify how interactions among predators are modified by plant species composition and whether these effects are consistent with the observed influence of plant species composition on aphid population suppression. Although plant density was shown to have no influence on the multi-predator effect on aphid population growth, plant composition had a marked effect. In wheat monoculture, Adalia and Chrysoperla mixed treatments caused greater suppression of M. dirhodum populations than expected. However this positive emergent effect was reversed to a negative multi-predator effect in wheat and faba bean polyculture. The behavioural observations revealed that although dominant individuals did not respond to the presence of faba bean plants, the behaviour of sub-dominants was affected markedly, consistent with their foraging for extra-floral nectar produced by the faba bean. This interaction between plant composition and predator community composition on the foraging behaviour of sub-dominants is thought to underlie the observed effect of plant composition on the multi-predator effect. Thus, the emergence of multi-predator effects is shown to be strongly influenced by

  14. Plant species composition alters the sign and strength of an emergent multi-predator effect by modifying predator foraging behaviour.

    Science.gov (United States)

    Wilby, Andrew; Anglin, Linda Anderson; Nesbit, Christopher M

    2013-01-01

    The prediction of pest-control functioning by multi-predator communities is hindered by the non-additive nature of species functioning. Such non-additivity, commonly termed an emergent multi-predator effect, is known to be affected by elements of the ecological context, such as the structure and composition of vegetation, in addition to the traits of the predators themselves. Here we report mesocosm experiments designed to test the influence of plant density and species composition (wheat monoculture or wheat and faba bean polyculture) on the emergence of multi-predator effects between Adalia bipunctata and Chrysoperla carnea, in their suppression of populations of the aphid Metopolophium dirhodum. The mesocosm experiments were followed by a series of behavioural observations designed to identify how interactions among predators are modified by plant species composition and whether these effects are consistent with the observed influence of plant species composition on aphid population suppression. Although plant density was shown to have no influence on the multi-predator effect on aphid population growth, plant composition had a marked effect. In wheat monoculture, Adalia and Chrysoperla mixed treatments caused greater suppression of M. dirhodum populations than expected. However this positive emergent effect was reversed to a negative multi-predator effect in wheat and faba bean polyculture. The behavioural observations revealed that although dominant individuals did not respond to the presence of faba bean plants, the behaviour of sub-dominants was affected markedly, consistent with their foraging for extra-floral nectar produced by the faba bean. This interaction between plant composition and predator community composition on the foraging behaviour of sub-dominants is thought to underlie the observed effect of plant composition on the multi-predator effect. Thus, the emergence of multi-predator effects is shown to be strongly influenced by plant species

  15. Effects of developmental asynchrony between Aedes triseriatus (Diptera:Culicidae) and its predator Toxorhynchites rutilus (Diptera:Culicidae).

    Science.gov (United States)

    Nannini, M A; Juliano, S A

    1997-07-01

    Newly hatched Toxorhynchites rutilus (Coquillet) were added to experimental populations of Aedes triseriatus (Say) at varying days after prey hatch to test the hypothesis that a developmental asynchrony of Ae. triseriatus and Tx. rutilus leads to escape from predation by Ae. triseriatus in small water bodies. Presence of Tx. rutilus significantly affected prey survivorship. Regression of survivorship [log10 (x + 1) transformed] versus days head start for prey yielded a small, but significant positive slope, indicating that survivorship increased slightly with an increasing number of days head start. For females, mean weight at emergence was not significantly affected by treatments; however, median days to emergence differed significantly between the treatments, with females taking significantly longer to emerge with Tx. rutilus absent than when the predator was present. For males, neither mean mass nor median days to emergence was significantly affected by treatments. Treatments had no significant effect on the frequency of deaths or on mean weight of Tx. rutilus. Thus, a developmental asynchrony between Tx. rutilus and Ae. Triseriatus appears to have no effects on the predator, but does have a weak effect on prey performance at high hatch densities.

  16. Estimation of predation by the larvae of Toxorhynchites splendens on the aquatic stages of Aedes aegypti.

    Science.gov (United States)

    Dominic Amalraj, D; Das, P K

    1998-03-01

    Predation by instars of Toxorhynchites splendens on aquatic stages of Aedes aegypti was studied by estimating functional response parameters such as attack rate (a') and handling time (Th) in the laboratory. The predator displayed typical type-II functional response, similar to that of most insect predators when presented with increasing densities of any given size class of prey. Second instar predator attacked prey significantly at higher rate than the other instars. Small prey were attacked at higher rate than the predation on larger prey. Except second instar predator, other instars showed significant reduction in a' with increase in Th. Foraging surface area did not influence the predation rate. Predation was high at high water temperature and this was more prominent in the second instar predator. However, prey handling time was independent of the water temperature. Modeling of the predation of mixed age populations of prey and the predator through this short-term functional response experiment is discussed.

  17. Nonconsumptive predator-driven mortality causes natural selection on prey.

    Science.gov (United States)

    Siepielski, Adam M; Wang, Jason; Prince, Garrett

    2014-03-01

    Predators frequently exert natural selection through differential consumption of their prey. However, predators may also cause prey mortality through nonconsumptive effects, which could cause selection if different prey phenotypes are differentially susceptible to this nonconsumptive mortality. Here we present an experimental test of this hypothesis, which reveals that nonconsumptive mortality imposed by predatory dragonflies causes selection on their damselfly prey favoring increased activity levels. These results are consistent with other studies of predator-driven selection, however, they reveal that consumption alone is not the only mechanism by which predators can exert selection on prey. Uncovering this mechanism also suggests that prey defensive traits may represent adaptations to not only avoid being consumed, but also for dealing with other sources of mortality caused by predators. Demonstrating selection through both consumptive and nonconsumptive predator mortality provides us with insight into the diverse effects of predators as an evolutionary force. © 2013 The Author(s). Evolution © 2013 The Society for the Study of Evolution.

  18. Skate Bathyraja spp. egg predation in the eastern Bering Sea.

    Science.gov (United States)

    Hoff, G R

    2009-01-01

    Predation on skate eggs by snails was examined for three skate species at seven nursery sites in three regions (north, middle and south) of the eastern Bering Sea. Mean predation levels were 6.46% for the Alaska skate Bathyraja parmifera, 2.65% for the Aleutian skate Bathyraja aleutica and 22.25% for the Bering skate Bathyraja interrupta. Predation levels were significantly higher at the middle and north sites than the south sites for all species combined. Predation levels decreased with increasing egg-case densities at all nursery sites, and the highest predation levels occurred where egg-case densities were very low. Predated egg-case density increased with increasing snail densities across all nursery sites examined. The Oregon triton Fusitriton oregonensis was the most abundant snail species at all nursery sites and displayed ability to drill holes in the egg case of B. parmifera. Holes left by predatory snails in egg cases of B. parmifera were significantly larger, and of different shape at the middle site compared to the south site. Holes in B. parmifera were also significantly larger than those in egg cases of B. interrupta across all sites examined. Egg cases of B. aleutica possess surface spines that cover the egg case and may inhibit predation by snails at a greater rate than that of the B. parmifera and B. interrupta, which have a smoother egg-case surface.

  19. Aquatic macroinvertebrate responses to native and non-native predators

    Directory of Open Access Journals (Sweden)

    Haddaway N. R.

    2014-01-01

    Full Text Available Non-native species can profoundly affect native ecosystems through trophic interactions with native species. Native prey may respond differently to non-native versus native predators since they lack prior experience. Here we investigate antipredator responses of two common freshwater macroinvertebrates, Gammarus pulex and Potamopyrgus jenkinsi, to olfactory cues from three predators; sympatric native fish (Gasterosteus aculeatus, sympatric native crayfish (Austropotamobius pallipes, and novel invasive crayfish (Pacifastacus leniusculus. G. pulex responded differently to fish and crayfish; showing enhanced locomotion in response to fish, but a preference for the dark over the light in response to the crayfish. P.jenkinsi showed increased vertical migration in response to all three predator cues relative to controls. These different responses to fish and crayfish are hypothesised to reflect the predators’ differing predation types; benthic for crayfish and pelagic for fish. However, we found no difference in response to native versus invasive crayfish, indicating that prey naiveté is unlikely to drive the impacts of invasive crayfish. The Predator Recognition Continuum Hypothesis proposes that benefits of generalisable predator recognition outweigh costs when predators are diverse. Generalised responses of prey as observed here will be adaptive in the presence of an invader, and may reduce novel predators’ potential impacts.

  20. Interactive effects of nutrient additions and predation on infaunal communities

    Science.gov (United States)

    Posey, M.H.; Alphin, T.D.; Cahoon, L.; Lindquist, D.; Becker, M.E.

    1999-01-01

    Nutrient additions represent an important anthropogenic stress on coastal ecosystems. At moderate levels, increased nutrients may lead to increased primary production and, possibly, to increased biomass of consumers although complex trophic interactions may modify or mask these effects. We examined the influence of nutrient additions and interactive effects of trophic interactions (predation) on benthic infaunal composition and abundances through small-scale field experiments in 2 estuaries that differed in ambient nutrient conditions. A blocked experimental design was used that allowed an assessment of direct nutrient effects in the presence and absence of predation by epibenthic predators as well as an assessment of the independent effects of predation. Benthic microalgal production increased with experimental nutrient additions and was greater when infaunal abundances were lower, but there were no significant interactions between these factors. Increased abundances of one infaunal taxa, Laeonereis culveri, as well as the grazer feeding guild were observed with nutrient additions and a number of taxa exhibited higher abundances with predator exclusion. In contrast to results from freshwater systems there were no significant interactive effects between nutrient additions and predator exclusion as was predicted. The infaunal responses observed here emphasize the importance of both bottom-up (nutrient addition and primary producer driven) and top-down (predation) controls in structuring benthic communities. These processes may work at different spatial and temporal scales, and affect different taxa, making observation of potential interactive effects difficult.

  1. Predation risk shapes social networks in fission-fusion populations.

    Directory of Open Access Journals (Sweden)

    Jennifer L Kelley

    Full Text Available Predation risk is often associated with group formation in prey, but recent advances in methods for analysing the social structure of animal societies make it possible to quantify the effects of risk on the complex dynamics of spatial and temporal organisation. In this paper we use social network analysis to investigate the impact of variation in predation risk on the social structure of guppy shoals and the frequency and duration of shoal splitting (fission and merging (fusion events. Our analyses revealed that variation in the level of predation risk was associated with divergent social dynamics, with fish in high-risk populations displaying a greater number of associations with overall greater strength and connectedness than those from low-risk sites. Temporal patterns of organisation also differed according to predation risk, with fission events more likely to occur over two short time periods (5 minutes and 20 minutes in low-predation fish and over longer time scales (>1.5 hours in high-predation fish. Our findings suggest that predation risk influences the fine-scale social structure of prey populations and that the temporal aspects of organisation play a key role in defining social systems.

  2. Predation as a landscape effect: the trading off by prey species between predation risks and protection benefits.

    Science.gov (United States)

    Mönkkönen, M; Husby, M; Tornberg, R; Helle, P; Thomson, R L

    2007-05-01

    1. Predators impose costs on their prey but may also provide benefits such as protection against other (e.g. nest) predators. The optimal breeding location in relation to the distance from a nesting raptor varies so as to minimize the sum of costs of adult and nest predation. We provide a conceptual model to account for variation in the relative predation risks and derive qualitative predictions for how different prey species should respond to the distance from goshawk Accipiter gentilis nests. 2. We test the model predictions using a comprehensive collection of data from northern Finland and central Norway. First, we carried out a series of experiments with artificial bird nests to test if goshawks may provide protection against nest predation. Second, we conducted standard bird censuses and nest-box experiments to detect how the density or territory occupancy of several prey species varies with distance from the nearest goshawk nest. 3. Nest predation rate increased with distance from goshawk nest indicating that goshawks may provide protection for birds' nests against nest predation. Abundance (or probability of presence) of the main prey species of goshawks peaked at intermediate distances from goshawk nests, reflecting the trade-off. The abundance of small songbird species decreased with distance from goshawk nests. The goshawk poses little risk to small songbirds and they may benefit from goshawk proximity in protection against nest predation. Finally, no pattern with distance in pied flycatcher territory (nest box) occupation rate or the onset of egg-laying was detected. This is expected, as flycatchers neither suffer from marked nest predation risk nor are favoured goshawk prey. 4. Our results suggest that territory location in relation to the nest of a predator is a trade-off situation where adult birds weigh the risk of themselves being predated against the benefits accrued from increased nest survival. Prey species appear able to detect and measure

  3. Nest Predation by Commensal Rodents in Urban Bushland Remnants.

    Directory of Open Access Journals (Sweden)

    Helen M Smith

    Full Text Available Exotic predators are a major threat to native wildlife in many parts of the world. Developing and implementing effective strategies to mitigate their effects requires robust quantitative data so that management can be evidence-based, yet in many ecosystems this is missing. Birds in particular have been severely impacted by exotic mammalian predators, and a plethora of studies on islands record predation of bird eggs, fledglings and adults by exotic species such as rodents, stoats and cats. By comparison, few studies have examined nest predation around mainland urban centres which often act as dispersal hubs, especially for commensal species such as rodents. Here, we experimentally examine nest predation rates in habitat patches with varying black rat (Rattus rattus densities in Sydney, Australia and test whether these exotic rats have the effects expected of exotic predators using effect size benchmarks. In the case where black rats have replaced native Rattus spp., we expected that black rats, being more arboreal than native Rattus spp., would be a significant source of predation on birds because they can readily access the arboreal niche where many birds nest. We tested this idea using above-ground artificial nests to represent those of typical small bird species such as the New Holland honeyeater (Phylidonyris novaehollandiae. We found that fewer eggs were depredated by rodents on sites where we removed black rats compared to unmanipulated sites, and that the effect size calculated from the total number of eggs surviving beyond the typical incubation period was similar to that expected for an exotic predator. Our results suggest that, although Australian birds have co-evolved with native Rattus species, in the case where black rats have replaced native Rattus species, exotic black rats appear to pose an additive source of predation on birds in remnant habitats, most likely due to their ability to climb more efficiently than their native

  4. Nest Predation by Commensal Rodents in Urban Bushland Remnants.

    Science.gov (United States)

    Smith, Helen M; Dickman, Chris R; Banks, Peter B

    2016-01-01

    Exotic predators are a major threat to native wildlife in many parts of the world. Developing and implementing effective strategies to mitigate their effects requires robust quantitative data so that management can be evidence-based, yet in many ecosystems this is missing. Birds in particular have been severely impacted by exotic mammalian predators, and a plethora of studies on islands record predation of bird eggs, fledglings and adults by exotic species such as rodents, stoats and cats. By comparison, few studies have examined nest predation around mainland urban centres which often act as dispersal hubs, especially for commensal species such as rodents. Here, we experimentally examine nest predation rates in habitat patches with varying black rat (Rattus rattus) densities in Sydney, Australia and test whether these exotic rats have the effects expected of exotic predators using effect size benchmarks. In the case where black rats have replaced native Rattus spp., we expected that black rats, being more arboreal than native Rattus spp., would be a significant source of predation on birds because they can readily access the arboreal niche where many birds nest. We tested this idea using above-ground artificial nests to represent those of typical small bird species such as the New Holland honeyeater (Phylidonyris novaehollandiae). We found that fewer eggs were depredated by rodents on sites where we removed black rats compared to unmanipulated sites, and that the effect size calculated from the total number of eggs surviving beyond the typical incubation period was similar to that expected for an exotic predator. Our results suggest that, although Australian birds have co-evolved with native Rattus species, in the case where black rats have replaced native Rattus species, exotic black rats appear to pose an additive source of predation on birds in remnant habitats, most likely due to their ability to climb more efficiently than their native counterparts

  5. Malaria and risk of predation: a comparative study of birds.

    Science.gov (United States)

    Møller, Anders Pape; Nielsen, Jan Tøttrup

    2007-04-01

    Predators have been hypothesized to prey on individuals in a poor state of health, although this hypothesis has only rarely been examined. We used extensive data on prey abundance and availability from two long-term studies of the European Sparrowhawk (Accipiter nisus) and the Eurasian Goshawk (Accipiter gentilis) to quantify the relationship between predation risk of different prey species and infection with malaria and other protozoan blood parasites. Using a total of 31 745 prey individuals of 65 species of birds from 1709 nests during 1977-1997 for the Sparrowhawk and a total of 21 818 prey individuals of 76 species of birds from 1480 nests for the Goshawk during 1977-2004, we show that prey species with a high prevalence of blood parasites had higher risks of predation than species with a low prevalence. That was also the case when a number of confounding variables of prey species, such as body mass, breeding sociality, sexual dichromatism, and similarity among species in risk of predation due to common descent, were controlled in comparative analyses of standardized linear contrasts. Prevalence of the genera Haemoproteus, Leucocytozoon, Plasmodium, and Trypanosoma were correlated with each other, and we partitioned out the independent effects of different protozoan genera on predation risk in comparative analyses. Prevalence of Haemoproteus, Leucocytozoon, and Plasmodium accounted for interspecific variation in predation risk for the two raptors. These findings suggest that predation is an important factor affecting parasite-host dynamics because predators tend to prey on hosts that are more likely to be infected, thereby reducing the transmission success of parasites. Furthermore, this study demonstrates that protozoan infections are a common cause of death for hosts mediated by increased risk of predation.

  6. Desert bighorn sheep lambing habitat: Parturition, nursery, and predation sites

    Science.gov (United States)

    Karsch, Rebekah C.; Cain, James W.; Rominger, Eric M.; Goldstein, Elise J.

    2016-01-01

    Fitness of female ungulates is determined by neonate survival and lifetime reproductive success. Therefore, adult female ungulates should adopt behaviors and habitat selection patterns that enhance survival of neonates during parturition and lactation. Parturition site location may play an important role in neonatal mortality of desert bighorn sheep (Ovis canadensis mexicana) when lambs are especially vulnerable to predation, but parturition sites are rarely documented for this species. Our objectives were to assess environmental characteristics at desert bighorn parturition, lamb nursery, and predation sites and to assess differences in habitat characteristics between parturition sites and nursery group sites, and predation sites and nursery group sites. We used vaginal implant transmitters (VITs) to identify parturition sites and capture neonates. We then compared elevation, slope, terrain ruggedness, and visibility at parturition, nursery, and lamb predation sites with paired random sites and compared characteristics of parturition sites and lamb predation sites to those of nursery sites. When compared to random sites, odds of a site being a parturition site were highest at intermediate slopes and decreased with increasing female visibility. Odds of a site being a predation site increased with decreasing visibility. When compared to nursery group sites, odds of a site being a parturition site had a quadratic relationship with elevation and slope, with odds being highest at intermediate elevations and intermediate slopes. When we compared predation sites to nursery sites, odds of a site being a predation were highest at low elevation areas with high visibility and high elevation areas with low visibility likely because of differences in hunting strategies of coyote (Canis latrans) and puma (Puma concolor). Parturition sites were lower in elevation and slope than nursery sites. Understanding selection of parturition sites by adult females and how habitat

  7. Does a Simple Cope's Rule Mechanism Overlook Predators?

    Directory of Open Access Journals (Sweden)

    Vincenzo Penteriani

    2007-01-01

    Full Text Available The Cope’s rule predicts a tendency for species to evolve towards an increase in size. Recently, it has been suggested that such a tendency is due to the fact that large body sizes provide a general increase in individual fitness. Here we highlight evidence that predator species do not always fit the large-size = high-fitness mechanism for Cope’s rule. Given the specific requirements of predators and the complexity of prey-predator relationships, any analysis that does not take into account all animal groups may overlook a significant portion of evolutive trends. Generalisations may not be possible regardless of taxa.

  8. The significance of facultative scavenging in generalist predator nutrition: detecting decayed prey in the guts of predators using PCR.

    Science.gov (United States)

    Foltan, Pavel; Sheppard, Samuel; Konvicka, Martin; Symondson, William O C

    2005-11-01

    Gut-content analyses using molecular techniques are an effective approach to quantifying predator-prey interactions. Predation is often assumed but scavenging is an equally likely route by which animal DNA enters the gut of a predator/scavenger. We used PCR (polymerase chain reaction) to detect scavenged material in predator gut homogenates. The rates at which DNA in decaying slugs (Mollusca: Pulmonata) and aphids (Homoptera: Aphididae) became undetectable were estimated. The detectability of DNA from both carrion types in the guts of the generalist predator Pterostichus melanarius (Coleoptera: Carabidae) was then determined. The effects of carrion age and weight, as well as beetle sex, on detection periods, were quantified. Laboratory trials measured prey preference of beetles between live and decaying prey. Further experiments measured, for the first time, feeding by P. melanarius on dead slugs and aphids directly in the field. In both field and laboratory, P. melanarius preferentially fed on dead prey if available, but preference changed as the prey became increasingly decayed. Disappearance rates for slug carrion in wheat fields and grasslands were estimated and P. melanarius was identified as the main scavenger. Comparison of the retention time for dead slugs in the field, with the detection period for decaying slug material in the guts of the predators, showed that PCR-based techniques are not able to distinguish between predated and scavenged food items. This could potentially lead to overestimation of the impact of predation on slugs (and other prey) by carabids. Possible implications of facultative scavenging by invertebrate predators for biocontrol and food-web research are discussed.

  9. Responses of urban crows to con- and hetero-specific alarm calls in predator and non-predator zoo enclosures.

    Science.gov (United States)

    Bílá, Kateřina; Beránková, Jana; Veselý, Petr; Bugnyar, Thomas; Schwab, Christine

    2017-01-01

    Urban animals and birds in particular are able to cope with diverse novel threats in a city environment such as avoiding novel, unfamiliar predators. Predator avoidance often includes alarm signals that can be used also by hetero-specifics, which is mainly the case in mixed-species flocks. It can also occur when species do not form flocks but co-occur together. In this study we tested whether urban crows use alarm calls of conspecifics and hetero-specifics (jackdaws, Corvus monedula) differently in a predator and a non-predator context with partly novel and unfamiliar zoo animal species. Birds were tested at the Tiergarten Schönbrunn in the city of Vienna by playing back con- and hetero-specific alarm calls and control stimuli (great tit song and no stimuli) at predator (wolf, polar bear) and non-predator (eland antelope and cranes, peccaries) enclosures. We recorded responses of crows as the percentage of birds flying away after hearing the playback (out of those present before the playback) and as the number of vocalizations given by the present birds. A significantly higher percentage of crows flew away after hearing either con- or hetero-specific alarm calls, but it did not significantly differ between the predator and the non-predator context. Crows treated jackdaw calls just as crow calls, indicating that they make proper use of hetero-specific alarm calls. Responding similarly in both contexts may suggest that the crows were uncertain about the threat a particular zoo animal represents and were generally cautious. In the predator context, however, a high percentage of crows also flew away upon hearing the great tit control song which suggests that they may still evaluate those species which occasionally killed crows as more dangerous and respond to any conspicuous sound.

  10. Pemangsaan Propagul Mangrove Rhizophora sp. Sebagai Bukti Teori Dominance-Predation (Predation of Mangrove Propagule, Rhizophora sp. as Evidence of Dominance-Predation Theory

    Directory of Open Access Journals (Sweden)

    Rudhi Pribadi

    2014-06-01

    Propagule predation on mangrove in some extent reduced its viability to grow into seedling. The predation could happened before (pre-dispersal or after (post-dispersal the propagule drop from the tree.The reasearch was conducted in Pasar Banggi, Rembang District, Central Java. The aim was to investigate the predation rate of Rhizophora mucronata Lamk., R. stylosa Griff. and R. apiculata Blume propagules pre-dispersal and post-dispersal. Firstly, preface experiment for find domination spesies in the location, Second, with applied descriptive-based survey sampling and field experiment methods. Than all propagules of five replication trees were harvested and checked for its condition on pre-dispersal step. The third, with post-dispersal study there were twenty propagules from each spesies and tied them with used nylon string and placed on the forest floor for 2 until 18 days and checked its condition every 2 days after placement. This study is also set for tested the Smith’s theory on propagule predation related to tree domination. Rhizophora stylosa propagule was  most predated before they fall (mean 61,06%, range 45,40-76,05%, followed by R. apiculata (mean 58,18%, range 47,41-68% and the lowest isR. mucronata with mean 11,88% (range 7,06-15,71%. After 18 days of experiment in the field R. stylosa propagule in R. stylosa–dominated area was the lowest predated (mean 46,67% compared to propagule in the area dominated by R. apiculata (63,33% and also in R. mucronata area (83,33 Predated R. mucronata propagule is the highest in the R. mucronata dominated area (mean 95% compared with R. apiculata dominated area (mean 55% and also in R. stylosa dominated area (45%. Pradated of R. apiculata propagule is the lowest in the domination area of R. apiculata (50% compared with R. stylosa area domination with (mean 70% also R. mucronata (73,33%. The result showed that the theory of dominance-predation can be proved only for R. stylosa and R. apiculata spesies, but not for R

  11. Endocrine Disruptors in Mediterranean top marine predators.

    Science.gov (United States)

    Fossi, M Cristina; Casini, Silvia; Marsili, Letizia

    2006-05-01

    Man-made Endocrine Disruptors (EDs) range across all continents and oceans. Some geographic areas are potentially more threatened than others: one of these is the Mediterranean Sea. Levels of some xenobiotics are much higher here than in other seas and oceans. In this paper we review the final results of a project in which the hypothesis that Mediterranean top predator species (such as large pelagic fish and marine mammals) are potentially at risk due to EDs was investigated. In a four-year survey on the Mediterranean population of swordfish (Xiphias gladius), the potential toxicological effects of organochlorine compounds (OCs) on specimens of swordfish and tuna fish (Thunnus thynnus thynnus), caught in the spawning seasons from 1999 to 2002 in the Straits of Messina, Sicily (Italy), were investigated using vitellogenin (Vtg), Zona radiata proteins (Zrp), and cytochrome P4501A (CYP1A) activities (EROD, BPMO). Tissues (skin and blubber) were obtained from Stenella coeruleoalba, Tursiops truncatus, Delphinus delphis and Balaenoptera physalus from the western Ligurian Sea, between Corsica and the French-Italian coast, and Ionic Sea using biopsy darts launched with a crossbow. Benzo(alpha)pyrene monoxigenase (BPMO) activity was mesured in biopsies and cholrinated hydrocarbon levels were detected. We illustrate the need to develop and apply sensitive methodological tools, such as biomarkers (Vitellogenin, Zona Radiata proteins and CYP1A activities) for evaluation of toxicological risk in Xiphias gladius and Thunnus thynnus thynnus), and nondestructive biomarkers (CYP1A activities and fibroblast cell culture in skin biopsy), for the hazard assessment of threatened marine mammals species (Stenella coeruleoalba, Tursiops truncatus, Delphinus delphis and Balaenoptera physalus) exposed to EDs. The present research shows that: a) Vtg and Zrp can be used as diagnostic tools for fish stocks hazard assessment in the Mediterranean Sea; b) that CYP1A1 (BPMO) induction in

  12. Predation of the Peach Aphid Myzus persicae by the mirid Predator Macrolophus pygmaeus on Sweet Peppers: Effect of Prey and Predator Density

    Directory of Open Access Journals (Sweden)

    Lara De Backer

    2015-06-01

    Full Text Available Integrated Pest Management strategies are widely implemented in sweet peppers. Aphid biological control on sweet pepers includes curative applications of parasitoids and generalist predators, but with limited efficiency. Macrolophus pygmaeus is a zoophytophagous predator which has been reported to predate on aphids, but has traditionally been used to control other pests, including whiteflies. In this work, we evaluate the effectiveness of M. pygmaeus in controlling Myzus persicae (Homoptera: Aphididae by testing different combinations of aphid and predator densities in cage-experiments under greenhouse conditions. The impact of the presence of an alternative factitious prey (E. kuehniella eggs was also investigated. Macrolophus pygmaeus, at densities of four individuals/plant, caused rapid decline of newly established aphid populations. When aphid infestations were heavy, the mirid bug reduced the aphid numbers but did not fully eradicate aphid populations. The availability of a factitious prey did not influence M. pygmaeus predation on aphids. Based on our data, preventive application of M. pygmaeus, along with a supplementary food source , is recommended to control early infestations of aphids.

  13. Chewing insect predation on artificial caterpillars is related to activity density of ground beetles (Coleoptera: Carabidae)

    DEFF Research Database (Denmark)

    Ferrante, M.; Lövei, G. L.

    2015-01-01

    In cultivated landscapes, predatory arthropods play an important role for pest control. Traditionally, monitoring their effect on pests was done using indirect measures (e.g. characterising predator activity by the numbers of predators caught). However, the contribution of predators to predation ...

  14. Nest predators of open and cavity nesting birds in oak woodlands

    Science.gov (United States)

    Kathryn L. Purcell; Jared Verner

    1999-01-01

    Camera setups revealed at least three species of rodents and seven species of birds as potential predators at artificial open nests. Surprisingly, among avian predators identified at open nests, one third were Bullock's Orioles (Icterus bullockii). Two rodent species and three bird species were potential predators at artificial cavity nests. This high predator...

  15. How do brent geese (Branta b. bernicla) cope with evil?; complex relationships between predators and prey

    NARCIS (Netherlands)

    Ebbinge, B.S.; Spaans, B.

    2002-01-01

    Actual predation is rarely observed in the field, and therefore the role of predators is often severely underestimated. Species are limited in their distribution, which is caused not only by predation but also by the anti-predator behaviour that prey-species have developed under the continuous

  16. Trophic cascade induced by molluscivore predator alters pore-water biogeochemistry via competitive release of prey

    NARCIS (Netherlands)

    van Gils, Jan A.; van der Geest, Matthijs; Jansen, Erik J.; Govers, Laura L.; de Fouw, Jimmy; Piersma, Theunis

    Effects of predation may cascade down the food web. By alleviating interspecific competition among prey, predators may promote biodiversity, but the precise mechanisms of how predators alter competition have remained elusive. Here we report on a predator-exclosure experiment carried out in a

  17. Trophic cascade induced by molluscivore predator alters pore-water biogeochemistry via competitive release of prey

    NARCIS (Netherlands)

    van Gils, J.A.; van der Geest, M.; Jansen, E.J.; Govers, L.L.; de Fouw, J.; Piersma, T.

    2012-01-01

    Effects of predation may cascade down the food web. By alleviating interspecific competition among prey, predators may promote biodiversity, but the precise mechanisms of how predators alter competition have remained elusive. Here we report on a predator-exclosure experiment carried out in a

  18. Antipredator behaviours of a spider mite in response to cues of dangerous and harmless predators.

    Science.gov (United States)

    Dias, Cleide Rosa; Bernardo, Ana Maria Guimarães; Mencalha, Jussara; Freitas, Caelum Woods Carvalho; Sarmento, Renato Almeida; Pallini, Angelo; Janssen, Arne

    2016-07-01

    Prey are known to invest in costly antipredator behaviour when perceiving cues of dangerous, but not of relatively harmless predators. Whereas most studies investigate one type of antipredator behaviour, we studied several types (changes in oviposition, in escape and avoidance behaviour) in the spider mite Tetranychus evansi in response to cues from two predatory mites. The predator Phytoseiulus longipes is considered a dangerous predator for T. evansi, whereas Phytoseiulus macropilis has a low predation rate on this prey, thus is a much less dangerous predator. Spider mite females oviposited less on leaf disc halves with predator cues than on clean disc halves, independent of the predator species. On entire leaf discs, they laid fewer eggs in the presence of cues of the dangerous predator than on clean discs, but not in the presence of cues of the harmless predator. Furthermore, the spider mites escaped more often from discs with cues of the dangerous predator than from discs without predator cues, but they did not escape more from discs with cues of the harmless predator. The spider mites did not avoid plants with conspecifics and predators. We conclude that the spider mites displayed several different antipredator responses to the same predator species, and that some of these antipredator responses were stronger with cues of dangerous predators than with cues of harmless predators.

  19. Modelling foraging movements of diving predators: a theoretical study exploring the effect of heterogeneous landscapes on foraging efficiency

    Directory of Open Access Journals (Sweden)

    Marianna Chimienti

    2014-09-01

    represents a useful starting point to understand the energetic reasons for a range of potential predator responses to spatial heterogeneity and environmental uncertainties in terms of search behaviour and predator–prey interactions. We highlight future directions that integrated empirical and modelling studies should take to improve our ability to predict how diving predators will be impacted by the deployment of manmade structures in the marine environment.

  20. Ratsnake response to bottomland flooding: implications for avian nest predation

    Directory of Open Access Journals (Sweden)

    Gerardo L.F. Carfagno

    2009-12-01

    Full Text Available Lower predation has been documented for birds’ nests located over water and a recent study found lower predation on wood duck (Aix sponsa nests in bottomland forest during flooding. In a three-year study we used radio telemetry to determine whether flooding affected use of bottomlands by ratsnakes (Elaphe obsoleta and thus might explain reduced nest predation. Of the 22 ratsnakes we tracked, only five used bottomlands and three of them did so exclusively, suggesting a surprising degree of habitat specialization by individual snakes. Those individuals regularly moved into flooded forest and their frequency of movement and distance moved appeared unaffected by flooding. Although it seems unlikely that ratsnakes leave bottomlands during floods, they may prey more extensively on small mammals that are restricted to trees when the forest is flooded, thereby reducing predation pressure on nesting birds.

  1. Nest predation and the species diversity of birds.

    Science.gov (United States)

    Ricklefs, R E

    1989-06-01

    In a recent series of papers, Thomas E. Martin has suggested that selective, density-dependent predation on nests may promote ecological diversification of birds and constrain the number of coexisting species in a community. In an experimental study, Martin has demonstrated density-dependent predation on artificial nests constructed and placed so as to mimic natural ones. Comparisons between habitats indicate that availability of suitable nest sites may influence community diversity more strongly than does diversity of foraging niches. Although his case is circumstantial at this point, Martin argues compellingly for considering predation more seriously in studies of community ecology. Indeed, many patterns attributed to competition for food resources may arise, instead, from the partitioning of predator-escape space. Copyright © 1989. Published by Elsevier Ltd.

  2. [Predator disease sampling results in Montana 1993-1995

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This document contains data from predator disease sampling in Montana for the reintroduction of black-footed ferrets at Charles M. Russell National Wildlife Refuge....

  3. How Predation and Landscape Fragmentation Affect Vole Population Dynamics

    DEFF Research Database (Denmark)

    Dalkvist, Trine; Sibly, Richard M.; Topping, Chris J.

    2011-01-01

    on vole population dynamics of making predators more specialised, of altering the breeding season, and increasing the level of habitat fragmentation. We found that fragmentation as well as the presence of specialist predators are necessary for the occurrence of population cycles. Habitat fragmentation......Background: Microtine species in Fennoscandia display a distinct north-south gradient from regular cycles to stable populations. The gradient has often been attributed to changes in the interactions between microtines and their predators. Although the spatial structure of the environment is known...... to influence predator-prey dynamics of a wide range of species, it has scarcely been considered in relation to the Fennoscandian gradient. Furthermore, the length of microtine breeding season also displays a north-south gradient. However, little consideration has been given to its role in shaping or generating...

  4. How predation and landscape fragmentation affect vole population dynamics

    DEFF Research Database (Denmark)

    Dalkvist, Trine; Sibly, Richard; Topping, Christopher John

    2011-01-01

    on vole population dynamics of making predators more specialised, of altering the breeding season, and increasing the level of habitat fragmentation. We found that fragmentation as well as the presence of specialist predators are necessary for the occurrence of population cycles. Habitat fragmentation......Background: Microtine species in Fennoscandia display a distinct north-south gradient from regular cycles to stable populations. The gradient has often been attributed to changes in the interactions between microtines and their predators. Although the spatial structure of the environment is known...... to influence predator-prey dynamics of a wide range of species, it has scarcely been considered in relation to the Fennoscandian gradient. Furthermore, the length of vole breeding season also displays a north-south gradient. However, little consideration has been given to its role in shaping or generating...

  5. Escaping peril: perceived predation risk affects migratory propensity

    DEFF Research Database (Denmark)

    Hulthén, Kaj; Chapman, Ben B.; Nilsson, P. Anders

    2015-01-01

    Although migratory plasticity is increasingly documented, the ecological drivers of plasticity are not well understood. Predation risk can influence migratory dynamics, but whether seasonal migrants can adjust their migratory behaviour according to perceived risk is unknown. We used electronic ta...

  6. Beyond food: a foundation species facilitates its own predator

    NARCIS (Netherlands)

    Agüera, A.; van de Koppel, J.; Jansen, J.M.; Smaal, A.C.; Bouma, T.J.

    2015-01-01

    Facilitation by foundation species can play a critical role in structuring ecological communities. As environmental stress increases, generally more organisms become dependent on the stress buffering provided by foundation species. As such, foundation species may even facilitate their own predators,

  7. Summary of predator management on WPA uplands and group recommendations

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The topic "Predator Management on Waterfowl Production Area Uplands" was debated during the ND Project Leaders Meeting on August 26, 1987. The pro and c on side of...

  8. Weed seed predation in organic and conventional fields

    DEFF Research Database (Denmark)

    Navntoft, S; Wratten, S D; Kristensen, K

    2009-01-01

    % in conventional fields although variation was high. Significantly different removal rates between the two field types were found only 9 m from the field edge with approximately four times higher losses of fathen seeds in organic fields. There was also a strong tendency towards higher seed losses at organic field......Enhanced biological control of weed seeds may improve sustainability of agricultural production. Biological control due to seed predation may be higher in organic fields because organic production generally supports more seed predators. To investigate such a difference, weed seed predation...... was studied in autumn in eight organic and eight conventional mixed cropping fields in New Zealand. Predation rates were estimated by observing removal rates of seeds of the annual weeds fathen or common lambsquarter (Chenopodium album) and Persian speedwell (Veronica persica). The seed losses were recorded...

  9. Cormorant predation on PIT-tagged lake fish

    DEFF Research Database (Denmark)

    Skov, Christian; Jepsen, Niels; Baktoft, Henrik

    2014-01-01

    (Perca fluviatilis). In addition, we quantify the level of age/size truncation that cormorant predation could introduce in a population of perch, an important fish for recreational angling as well as for trophic interactions and ecosystem function in European lakes. Based on three years of PIT tagging......The present study use data from recovered PIT (Passive Integrated Transponder) tags to explore species-and size-specific annual predation rates by cormorants on three common lacustrine fishes (size range 120-367 mm) in a European lake; roach (Rutilus rutilus), common bream (Abramis brama) and perch...... of fish in Lake Viborg and subsequent recoveries of PIT tags from nearby cormorant roosting and breeding sites, we show that cormorants are major predators of roach, bream and perch within the size groups we investigated and for all species larger individuals had higher predation rates. Perch appear...

  10. Predation of schistosomiasis vector snails by ostracoda (crustacea)

    Science.gov (United States)

    Sohn, I.G.; Kornicker, L.S.

    1972-01-01

    An ostracod species of Cypretta is an effective predator in laboratory experiments on 1- to 3-day-old Biomphalaria glabrata, a vector snail of the blood fluke that causes the tropical and subtropical disease schistosomiasis.

  11. Colour Polymorphism Protects Prey Individuals and Populations Against Predation.

    Science.gov (United States)

    Karpestam, Einat; Merilaita, Sami; Forsman, Anders

    2016-02-23

    Colour pattern polymorphism in animals can influence and be influenced by interactions between predators and prey. However, few studies have examined whether polymorphism is adaptive, and there is no evidence that the co-occurrence of two or more natural prey colour variants can increase survival of populations. Here we show that visual predators that exploit polymorphic prey suffer from reduced performance, and further provide rare evidence in support of the hypothesis that prey colour polymorphism may afford protection against predators for both individuals and populations. This protective effect provides a probable explanation for the longstanding, evolutionary puzzle of the existence of colour polymorphisms. We also propose that this protective effect can provide an adaptive explanation for search image formation in predators rather than search image formation explaining polymorphism.

  12. A review of underwater bio-mimetic propulsion: cruise and fast-start

    Science.gov (United States)

    Chao, Li-Ming; Cao, Yong-Hui; Pan, Guang

    2017-08-01

    This paper reviews recent developments in the understanding of underwater bio-mimetic propulsion. Two impressive models of underwater propulsion are considered: cruise and fast-start. First, we introduce the progression of bio-mimetic propulsion, especially underwater propulsion, where some primary conceptions are touched upon. Second, the understanding of flapping foils, considered as one of the most efficient cruise styles of aquatic animals, is introduced, where the effect of kinematics and the shape and flexibility of foils on generating thrust are elucidated respectively. Fast-start propulsion is always exhibited when predator behaviour occurs, and we provide an explicit introduction of corresponding zoological experiments and numerical simulations. We also provide some predictions about underwater bio-mimetic propulsion.

  13. Seed production and predation in a changing climate: new roles for resource and seed predator feedback?

    Science.gov (United States)

    Solbreck, Christer; Knape, Jonas

    2017-09-01

    Climate change may cause changes in the dynamics of populations beyond comparatively simple directional effects. To better understand complex effects on dynamics requires long-term studies of populations that experience changes in climatic conditions. We study the dynamics of a seed-production-seed-predation system, consisting of a perennial herb and its two seed predatory insects, over a 40-yr period during which climate change has caused the annual growing season to increase by 20 d. During this period, plant patches have increased almost threefold in size and seed production has slipped into a pattern of alternate high and low years with a higher variance than in the beginning of the period. We find that seed production is associated with precipitation of the present summer and a non-linear feedback from seed production of the previous year. When previous year's seed production is low, weather forcing and unexplained noise determine the extent of seed production. When previous seed production is high, depleted resources limit seed production. Resource depletion happened frequently in the latter parts of the study but rarely in the beginning. The changing patterns of seed production in turn affect the dynamics of seed predation, which is dominated by one of the seed predators. Its dynamics are strongly linked to seed density fluctuations, but its population growth rate is satiated when resource fluctuations become too large. In the latter part of the study period, when seed fluctuations were alternating between years of high and low density, satiation was common and there was a large increase in surviving seeds in good years. Our study illustrates that a changing climate can fundamentally influence patterns of long-term dynamics at multiple trophic levels. © 2017 by the Ecological Society of America.

  14. California current system - Predators and the preyscape

    Science.gov (United States)

    Ainley, David G.; Adams, Peter B.; Jahncke, Jaime

    2015-06-01

    The preyscape of the California Current System (CCS), one of the most productive marine areas on Earth (Glantz and Thompson, 1981), is highly variable, as evidenced by the papers in this issue, and as such presents a challenge to Ecosystem-based fishery management (EBFM), which attempts to integrate ecosystem considerations as part of fishery management and conservation decisions. Approaches to EBFM for the waters off Washington, Oregon, and California, the CCS, have been initiated (PFMC, 2007, 2013), and are continually being developed. To inform this process, a workshop was held in September 2013 to: i) gather together the existing information on forage fish and predator dynamics in the CCS; ii) consider temporal (seasonal, annual, decadal) and spatial availability of prey complexes and why these patterns of availability occur and change; iii) summarize and present that information for discussion to a large range of experts in oceanography, fish and fisheries management, seabirds, marine mammals, and ecosystem management; and, iv) synthesize this information to be useable by fishery agencies. The papers in this special Journal of Marine Systems issue address these four points. While the full results and recommendations can be found here - "http://www.pointblue.org/uploads/assets/calcurrent/REPORT_Forage_Fish_Workshop_FINAL.pdf"

  15. Red queen dynamics in specific predator-prey systems.

    Science.gov (United States)

    Harris, Terence; Cai, Anna Q

    2015-10-01

    The dynamics of a predator-prey system are studied, with a comparison of discrete and continuous strategy spaces. For a [Formula: see text] system, the average strategies used in the discrete and continuous case are shown to be the same. It is further shown that the inclusion of constant prey switching in the discrete case can have a stabilising effect and reduce the number of available predator types through extinction.

  16. Bird productivity and nest predation in agricultural grasslands

    Science.gov (United States)

    Ribic, Christine; Guzy, Michael J.; Anderson, Travis J.; Sample, David W.; Nack, Jamie L.

    2012-01-01

    Effective conservation strategies for grassland birds in agricultural landscapes require understanding how nesting success varies among different grassland habitats. A key component to this is identifying nest predators and how these predators vary by habitat. We quantified nesting activity of obligate grassland birds in three habitats [remnant prairie, cool-season grass Conservation Reserve Program (CRP) fields, and pastures) in southwest Wisconsin, 2002-2004. We determined nest predators using video cameras and examined predator activity using track stations. Bobolink (Dolichonyx oryzivorus) and Henslow's Sparrow (Ammodramus henslowii) nested primarily in CRP fields, and Grasshopper Sparrow (A. savannarum) in remnant prairies. Eastern Meadowlark (Sturnella magna) nested evenly across all three habitats. Daily nest survival rate for Eastern Meadowlark varied by nesting stage alone. Daily nest survival rate for Grasshopper Sparrow varied by nest vegetation and distance to the nearest woody edge; nest survival was higher near woody edges. In CRP fields, most predators were grassland-associated, primarily thirteen-lined ground squirrels (Ictidomys tridecemlineatus). In pastures, one-third of the nest predators were grassland-associated (primarily thirteen-lined ground squirrels) and 56% were associated with woody habitats (primarily raccoons, Procyon lotor). Raccoon activity was greatest around pastures and lowest around prairies; regardless of habitat, raccoon activity along woody edges was twice that along non-woody edges. Thirteen-lined ground squirrel activity was greater along prairie edges than pastures and was greater along nonwoody edges compared to woody edges. In CRP fields, raccoon activity was greater along edges compared to the interiors; for ground squirrels these relationships were reversed. Using video camera technology to identify nest predators was indispensable in furthering our understanding of the grassland system. The challenge is to use that

  17. Predation vulnerability of planktonic copepods: consequences of predator foraging strategies and prey sensory abilities

    DEFF Research Database (Denmark)

    Viitasalo, M; Kiørboe, T; Flinkman, J.

    1998-01-01

    and from an artificial flow field, and the results were used in a model of hydrodynamic disturbance generated by a predator. The copepods detected mysids from a significantly larger distance than they detected sticklebacks (0.45 and 0.24 cm, respectively). Consequently, the capture success...... of the sticklebacks was higher than that of mysids. In the case of sticklebacks foraging on E. affinis, copepod reaction distance was significantly correlated with stickleback approaching speed; sticklebacks captured a copepod only if they were able to slowly approach to within a strike distance of...

  18. The effects of seasonally variable dragonfly predation on butterfly assemblages.

    Science.gov (United States)

    Tiitsaar, Anu; Kaasik, Ants; Teder, Tiit

    2013-01-01

    Where predation is seasonally variable, the potential impact of a predator on individual prey species will critically depend on phenological synchrony of the predator with the prey. Here we explored the effects of seasonally variable predation in multispecies assemblages of short-lived prey. The study was conducted in a landscape in which we had previously demonstrated generally high, but spatially and seasonally variable dragonfly-induced mortality in adult butterflies. In this system, we show that patterns of patch occupancy in butterfly species flying during periods of peak dragonfly abundance are more strongly associated with spatial variation in dragonfly abundance than patch occupancy of species flying when dragonfly density was low. We provide evidence indicating that this differential sensitivity of different butterfly species to between-habitat differences in dragonfly abundance is causally tied to seasonal variation in the intensity of dragonfly predation. The effect of dragonfly predation could also be measured at the level of whole local butterfly assemblages. With dragonfly density increasing, butterfly species richness decreased, and butterfly species composition tended to show a shift toward a greater proportion of species flying during periods of off-peak dragonfly abundance.

  19. Predation of Ladybird Beetles (Coleoptera: Coccinellidae) by Amphibians.

    Science.gov (United States)

    Sloggett, John J

    2012-07-18

    Studies of predation of ladybird beetles (Coccinellidae) have focused on a limited number of predator taxa, such as birds and ants, while other potential predators have received limited attention. I here consider amphibians as predators of ladybirds. Published amphibian gut analyses show that ladybirds are quite often eaten by frogs and toads (Anura), with recorded frequencies reaching up to 15% of dietary items. Salamanders (Caudata) eat ladybirds less frequently, probably as their habits less often bring them into contact with the beetles. Amphibians do not appear to be deleteriously affected by the potentially toxic alkaloids that ladybirds possess. Amphibians, especially frogs and toads, use primarily prey movement as a release cue to attack their food; it is thus likely that their ability to discriminate against ladybirds and other chemically defended prey is limited. Because of this poor discriminatory power, amphibians have apparently evolved non-specific resistance to prey defensive chemicals, including ladybird alkaloids. Although amphibian-related ladybird mortality is limited, in certain habitats it could outweigh mortality from more frequently studied predators, notably birds. The gut analyses from the herpetological literature used in this study, suggest that in studying predation of insects, entomologists should consider specialized literature on other animal groups.

  20. Bagworm bags as portable armour against invertebrate predators.

    Science.gov (United States)

    Sugiura, Shinji

    2016-01-01

    Some animals have evolved the use of environmental materials as "portable armour" against natural enemies. Portable bags that bagworm larvae (Lepidoptera: Psychidae) construct using their own silk and plant parts are generally believed to play an important role as a physical barrier against natural enemies. However, no experimental studies have tested the importance of bags as portable armour against predators. To clarify the defensive function, I studied the bagworm Eumeta minuscula and a potential predator Calosoma maximoviczi (Coleoptera: Carabidae). Under laboratory conditions, all bagworm larvae were attacked by carabid adults, but successfully defended themselves against the predators' mandibles using their own bags. The portable bags, which are composed mainly of host plant twigs, may function as a physical barrier against predator mandibles. To test this hypothesis, I removed the twig bags and replaced some with herb leaf bags; all bag-removed larvae were easily caught and predated by carabids, while all bag-replaced larvae could successfully defend themselves against carabid attacks. Therefore, various types of portable bags can protect bagworm larvae from carabid attacks. This is the first study to test the defensive function of bagworm portable bags against invertebrate predators.

  1. Fighting parasites and predators: How to deal with multiple threats?

    Directory of Open Access Journals (Sweden)

    Hesse Olivia

    2012-07-01

    Full Text Available Abstract Background Although inducible defences have been studied extensively, only little is known about how the presence of parasites might interfere with these anti-predator adaptations. Both parasites and predators are important factors shaping community structure and species composition of ecosystems. Here, we simultaneously exposed Daphnia magna to predator cues (released by the tadpole shrimp, Triops, or by a fish and spores of the yeast parasite Metschnikowia sp. to determine how life history and morphological inducible defences against these two contrasting types of predators are affected by infection. Results The parasite suppressed some Triops-induced defences: Daphnia lost the ability to produce a greater number of larger offspring, a life-history adaptation to Triops predation. In contrast, the parasite did not suppress inducible defences against fish: induction (resulting in smaller body length of the mothers as well as of their offspring and infection acted additively on the measured traits. Thus, fish-induced defences may be less costly than inducible defences against small invertebrate predators like Triops; the latter defences could no longer be expressed when the host had already invested in fighting off the parasite. Conclusions In summary, our study suggests that as specific inducible defences differ in their costs, some might be suppressed if a target prey is additionally infected. Therefore, adding parasite pressure to predator–prey systems can help to elucidate the costs of inducible defences.

  2. Intraguild predation and cannibalism among larvae of detritivorous caddisflies in subalpine wetlands

    Science.gov (United States)

    Wissinger, S.A.; Sparks, G.B.; Rouse, G.L.; Brown, W.S.; Steltzer, Heidi

    1996-01-01

    Comparative data from subalpine wetlands in Colorado indicate that larvae of the limnephilid caddisflies, Asynarchus nigriculus and Limnephilus externus, are reciprocally abundant among habitats - Limnephilus larvae dominate in permanent waters, whereas Asynarchus larvae dominate in temporary basins. The purpose of this paper is to report on field and laboratory experiments that link this pattern of abundance to biotic interactions among larvae. In the first field experiment, growth and survival were compared in single and mixed species treatments in littoral enclosures. Larvae, which eat mainly vascular plant detritus, grew at similar rates among treatments in both temporary and permanent habitats suggesting that exploitative competition is not important under natural food levels and caddisfly densities. However, the survival of Limnephilus larvae was reduced in the presence of Asynarchus larvae. Subsequent behavioral studies in laboratory arenas revealed that Asynarchus larvae are extremely aggressive predators on Limnephilus larvae. In a second field experiment we manipulated the relative sizes of larvae and found that Limnephilus larvae were preyed on only when Asynarchus larvae had the same size advantage observed in natural populations. Our data suggest that the dominance of Asynarchus larvae in temporary habitats is due to asymmetric intraguild predation (IGP) facilitated by a phenological head start in development. These data do not explain the dominance of Limnephilus larvae in permanent basins, which we show elsewhere to be an indirect effect of salamander predation. Behavioral observations also revealed that Asynarchus larvae are cannibalistic. In contrast to the IGP on Limnephilus larvae, Asynarchus cannibalism occurs among same-sized larvae and often involves the mobbing of one victim by several conspecifics. In a third field experiment, we found that Asynarchus cannibalism was not density-dependent and occurred even at low larval densities. We

  3. Development of a System-Wide Predator Control Program: Stepwise Implementation of a Predation Index, Predator Control Fisheries, and Evaluation Plan in the Columbia River Basin; Northern Pikeminnow Management Program, 2000 Annual Report.

    Energy Technology Data Exchange (ETDEWEB)

    Porter, Russell G.; Glaser, Bryce G.; Amren, Jennifer

    2003-03-01

    This report presents results for year ten in a basin-wide program to harvest northern pikeminnow (Ptychocheilus oregonensis). This program was started in an effort to reduce predation by northern pikeminnow on juvenile salmonids during their emigration from natal streams to the ocean. Earlier work in the Columbia River Basin suggested predation by northern pikeminnow on juvenile salmonids might account for most of the 10-20% mortality juvenile salmonids experience in each of eight Columbia River and Snake River reservoirs. Modeling simulations based on work in John Day Reservoir from 1982 through 1988 indicated that, if predator-size northern pikeminnow were exploited at a 10-20% rate, the resulting restructuring of their population could reduce their predation on juvenile salmonids by 50%. To test this hypothesis, we implemented a sport-reward angling fishery and a commercial longline fishery in the John Day Pool in 1990. We also conducted an angling fishery in areas inaccessible to the public at four dams on the mainstem Columbia River and at Ice Harbor Dam on the Snake River. Based on the success of these limited efforts, we implemented three test fisheries on a system-wide scale in 1991--a tribal longline fishery above Bonneville Dam, a sport-reward fishery, and a dam-angling fishery. Low catch of target fish and high cost of implementation resulted in discontinuation of the tribal longline fishery. However, the sport-reward and dam-angling fisheries were continued in 1992 and 1993. In 1992, we investigated the feasibility of implementing a commercial longline fishery in the Columbia River below Bonneville Dam and found that implementation of this fishery was also infeasible. Estimates of combined annual exploitation rates resulting from the sport-reward and damangling fisheries remained at the low end of our target range of 10-20%. This suggested the need for additional effective harvest techniques. During 1991 and 1992, we developed and tested a modified

  4. Predators in low arctic tundra and their impact on community structure and dynamics

    OpenAIRE

    Aunapuu, Maano

    2004-01-01

    The abundance of predators and their impact on ecosystem dynamics is a vividly discussed topic in current ecology. In my studies, incorporating field observations, field experiments and theoretical modeling, I explored the importance of predators and predation in a low arctic tundra ecosystem in northern Norway. This involved observing the abundance and spatial activity of predators (raptors and small mustelids); manipulating the abundance of predators (spiders and birds) in an arthropod comm...

  5. Interactive effects of prey refuge and additional food for predator in a diffusive predator-prey system

    DEFF Research Database (Denmark)

    Chakraborty, Subhendu; Tiwari, P. K.; Sasmal, S.K.

    2017-01-01

    Additional food for predators has been considered as one of the best established techniques in integrated pest management and biological conservation programs. In natural systems, there are several other factors, e.g., prey refuge, affect the success of pest control. In this paper, we analyze...... a predator-prey system with prey refuge and additional food for predator apart from the focal prey in the presence of diffusion. Our main aim is to study the interactive effects of prey refuge and additional food on the system dynamics and especially on the controllability of prey (pest). Different types...... of Turing patterns such as stripes, spots, holes, and mixtures of them are obtained. It is found that the supply of additional food to the predator is unable to control the prey (pest) population when prey refuge is high. Moreover, when both prey refuge and additional food are low, spatial distribution...

  6. starting infants on antiretroviral therapy clinical: paediatrics

    African Journals Online (AJOL)

    CHARACTERISTICS OF CHILDREN STARTING ART. A literature review of 30 paediatric studies or treatment programmes found that children receiving ART ranged from infants aged 2 months to adolescents aged 15 years.5 Of 26 studies that reported age at ART initiation,. 19 (73%) showed a mean or median age at start ...

  7. Lean and global technology start-ups

    DEFF Research Database (Denmark)

    Tanev, Stoyan; Rasmussen, Erik Stavnsager; Zijdemans, Erik

    2015-01-01

    In this paper the authors introduce the concept of Lean Global Start-up (LGS) as a way of emphasizing the impossibility for new technology start-ups to deal separately with business development, innovation and early internationalization. For a newly established technology firm the task of being...

  8. When Do Start-Ups Make Sense?

    Science.gov (United States)

    Langemeyer, Clement J.

    2005-01-01

    The start-up has received considerable attention in the last few years. While the National Research Council of Canada has generated many start-ups over its 88-year history, the creation of a formal entrepreneurship programme in the mid-1990s dramatically accelerated the pace at which they were created. Many factors come into play in the decision…

  9. 76 FR 14841 - Head Start Program

    Science.gov (United States)

    2011-03-18

    ... eligibility information. Programs should be especially sensitive to any potential domestic violence issues... HUMAN SERVICES Administration for Children and Families 45 CFR Part 1305 RIN 0970-AC46 Head Start Program AGENCY: Office of Head Start (OHS), Administration for Children and Families (ACF), Department of...

  10. Early exposure to nonlethal predation risk by size-selective predators increases somatic growth and decreases size at adulthood in threespined sticklebacks

    National Research Council Canada - National Science Library

    Bell, A. M; Dingemanse, N. J; Hankison, S. J; Langenhof, M. B. W; Rollins, K

    2011-01-01

    .... When cues of trout were present, juvenile sticklebacks grew faster. The increase in body size as a result of exposure to cues of predators was adaptive because larger individuals were more likely to survive predation...

  11. Effects of climate and exurban development on nest predation and predator presence in the southern Appalachian Mountains (USA).

    Science.gov (United States)

    Lumpkin, Heather A; Pearson, Scott M; Turner, Monica G

    2012-08-01

    In the eastern United States, land-use and climate change have likely contributed to declines in the abundance of Neotropical migrant birds that occupy forest interiors, but the mechanisms are not well understood. We conducted a nest-predation experiment in southern Appalachian Mountain forests (North Carolina, U.S.A.) during the 2009 and 2010 breeding seasons to determine the effects of exurban development and temperature on predator presence and the average number of days until eggs in an artificial nest were disturbed by predators. We baited artificial nests with quail (Excalfactoria chinensi) eggs and monitored them for 18 days. We used clay eggs, track plates, and motion-triggered cameras to detect and identify nest predators. The average number of days a nest was undisturbed decreased as mean temperature increased and, to a lesser extent, as the density of buildings increased. Nests on the ground were more often depredated than those in trees, likely due to increased predation by opossum (Didelphis virginiana) and other carnivores. Raccoons (Procyon lotor), opossums, corvids (Corvus brachyrhynchos and Cyanocitta cristata), chipmunks (Tamias striatus), black bears (Ursus americanus), and domestic cats (Felis catus) were the most commonly detected predators. Presence of these predators did not vary as a function of mean temperature. Domestic cats and corvids were detected more frequently in plots with high rather than low densities of buildings. Forest-interior specialists and Neotropical migrants often nest in cool, high-elevation areas with low housing density. These bird species, especially those that nest on the ground, may be most vulnerable to increased nest predation if temperature and exurban development increase at higher elevations as anticipated. ©2012 Society for Conservation Biology.

  12. Pengujian Perilaku Predator dan Anti-Predator pada Ikan Lele Dumbo (Clarias gariepinus Burchell, 1822) Transgenik F3

    OpenAIRE

    Widyawati, Putri

    2015-01-01

    African catfish (Clarias gariepinus) transgenic F3 containing Pangasius hypothalmus growth hormone (PhGH) genes can growth twice the average weight of the control population. However, before transgenic African catfish are released and utilized, their genetic impact on the natural environment must be examined. Predator avoidance is one of the major fitness traits determining potential environment risk. To determine the predator avoidance ability and growth performance of transgenic African cat...

  13. Plant defences limit herbivore population growth by changing predator-prey interactions.

    Science.gov (United States)

    Kersch-Becker, Mônica F; Kessler, André; Thaler, Jennifer S

    2017-09-13

    Plant quality and predators are important factors affecting herbivore population growth, but how they interact to regulate herbivore populations is not well understood. We manipulated jasmonate-induced plant resistance, exposure to the natural predator community and herbivore density to test how these factors jointly and independently affect herbivore population growth. On low-resistance plants, the predator community was diverse and abundant, promoting high predator consumption rates. On high-resistance plants, the predator community was less diverse and abundant, resulting in low predator consumption rate. Plant resistance only directly regulated aphid population growth on predator-excluded plants. When predators were present, plant resistance indirectly regulated herbivore population growth by changing the impact of predators on the herbivorous prey. A possible mechanism for the interaction between plant resistance and predation is that methyl salicylate, a herbivore-induced plant volatile attractive to predators, was more strongly induced in low-resistance plants. Increased plant resistance reduced predator attractant lures, preventing predators from locating their prey. Low-resistance plants may regulate herbivore populations via predators by providing reliable information on prey availability and increasing the effectiveness of predators. © 2017 The Author(s).

  14. Habitat complexity and sex-dependent predation of mosquito larvae in containers

    Science.gov (United States)

    Griswold, Marcus W.; Lounibos, L. Philip

    2012-01-01

    Studies in aquatic systems have shown that habitat complexity may provide refuge or reduce the number of encounters prey have with actively searching predators. For ambush predators, habitat complexity may enhance or have no effect on predation rates because it conceals predators, reduces prey detection by predators, or visually impairs both predators and prey. We investigated the effects of habitat complexity and predation by the ambush predators Toxorhynchites rutilus and Corethrella appendiculata on their mosquito prey Aedes albopictus and Ochlerotatus triseriatus in container analogs of treeholes. As in other ambush predator-prey systems, habitat complexity did not alter the effects of T. rutilus or C. appendiculata whose presence decreased prey survivorship, shortened development time, and increased adult size compared to treatments where predators were absent. Faster growth and larger size were due to predator-mediated release from competition among surviving prey. Male and female prey survivorship were similar in the absence of predators, however when predators were present, survivorship of both prey species was skewed in favor of males. We conclude that habitat complexity is relatively unimportant in shaping predator-prey interactions in this treehole community, where predation risk differs between prey sexes. PMID:16041612

  15. Anti-predator meshing may provide greater protection for sea turtle nests than predator removal.

    Directory of Open Access Journals (Sweden)

    Julie M O'Connor

    Full Text Available The problem of how to protect sea turtle nests from terrestrial predators is of worldwide concern. On Queensland's southern Sunshine Coast, depredation of turtle nests by the introduced European red fox (Vulpes vulpes has been recorded as the primary terrestrial cause of egg and hatchling mortality. We investigated the impact of foxes on the nests of the loggerhead turtle (Caretta caretta and occasional green turtle (Chelonia mydas over ten nesting seasons. Meshing of nests with fox exclusion devices (FEDs was undertaken in all years accompanied by lethal fox control in the first five-year period, but not in the second five-year period. Lethal fox control was undertaken in the study area from 2005 to February 2010, but foxes still breached 27% (range19-52% of turtle nests. In the second five-year period, despite the absence of lethal fox control, the average percentage of nests breached was less than 3% (range 0-4%. Comparison of clutch depredation rates in the two five-year periods demonstrated that continuous nest meshing may be more effective than lethal fox control in mitigating the impact of foxes on turtle nests. In the absence of unlimited resources available for the eradication of exotic predators, the use of FEDs and the support and resourcing of a dedicated volunteer base can be considered an effective turtle conservation tool on some beaches.

  16. Anti-predator meshing may provide greater protection for sea turtle nests than predator removal

    Science.gov (United States)

    O’Connor, Julie M.; Limpus, Colin J.; Hofmeister, Kate M.; Allen, Benjamin L.; Burnett, Scott E.

    2017-01-01

    The problem of how to protect sea turtle nests from terrestrial predators is of worldwide concern. On Queensland’s southern Sunshine Coast, depredation of turtle nests by the introduced European red fox (Vulpes vulpes) has been recorded as the primary terrestrial cause of egg and hatchling mortality. We investigated the impact of foxes on the nests of the loggerhead turtle (Caretta caretta) and occasional green turtle (Chelonia mydas) over ten nesting seasons. Meshing of nests with fox exclusion devices (FEDs) was undertaken in all years accompanied by lethal fox control in the first five-year period, but not in the second five-year period. Lethal fox control was undertaken in the study area from 2005 to February 2010, but foxes still breached 27% (range19–52%) of turtle nests. In the second five-year period, despite the absence of lethal fox control, the average percentage of nests breached was less than 3% (range 0–4%). Comparison of clutch depredation rates in the two five-year periods demonstrated that continuous nest meshing may be more effective than lethal fox control in mitigating the impact of foxes on turtle nests. In the absence of unlimited resources available for the eradication of exotic predators, the use of FEDs and the support and resourcing of a dedicated volunteer base can be considered an effective turtle conservation tool on some beaches. PMID:28187181

  17. Indirect interactions between browsers and seed predators affect the seed bank dynamics of a chaparral shrub.

    Science.gov (United States)

    Deveny, Adrian J; Fox, Laurel R

    2006-11-01

    Interactions between herbivores and seed predators may have long-term consequences for plant populations that rely on persistent seed banks for recovery after unpredictable fires. We assessed the effects of browsing by deer and seed predation by rodents, ants and birds on the densities of seeds entering the seed bank of Ceanothus cuneatus var. rigidus, a maritime chaparral shrub in coastal California. Ceanothus produced many more seeds when protected from browsers in long-term experimental exclosures than did browsed plants, but the seed densities in the soil beneath browsed and unbrowsed Ceanothus were the same at the start of an intensive one-year study. The density of seeds in the soil initially increased in both treatments following summer seed drop: while densities returned to pre-drop levels within a few weeks under browsed plants, soil seed densities remained high for 5-8 months beneath unbrowsed plants. Rodent abundance (especially deer mice) was higher near unbrowsed plants than >30 m away, and rodents removed Ceanothus seeds from dishes in the experimental plots. At least in the short term, rodent density and rates of seed removal were inversely related to the intensity of browsing. Our data have management implications for maintaining viable Ceanothus populations by regulating the intensity of browsing and the timing, intensity and frequency of fires.

  18. Anatomy of predator snail Huttonella bicolor, an invasive species in Amazon rainforest, Brazil (Pulmonata, Streptaxidae

    Directory of Open Access Journals (Sweden)

    Luiz Ricardo L. Simone

    2013-01-01

    Full Text Available The morpho-anatomy of the micro-predator Huttonella bicolor (Hutton, 1838 is investigated in detail. The species is a micro-predator snail, which is splaying in tropical and subtropical areas all over the world, the first report being from the Amazon Rainforest region of northern Brazil. The shell is very long, with complex peristome teeth. The radula bears sharp pointed teeth. The head lacks tentacles, bearing only ommatophores. The pallial cavity lacks well-developed vessels (except for pulmonary vessel; the anus and urinary aperture are on pneumostome. The kidney is solid, with ureter totally closed (tubular; the primary ureter is straight, resembling orthurethran fashion. The buccal mass has an elongated and massive odontophore, of which muscles are described; the odontophore cartilages are totally fused with each other. The salivary ducts start as one single duct, bifurcating only prior to insertion. The mid and hindguts are relatively simple and with smooth inner surfaces; there is practically no intestinal loop. The genital system has a zigzag-fashioned fertilization complex, narrow prostate, no bursa copulatrix, short and broad vas deferens, and simple penis with gland at distal tip. The nerve ring bears three ganglionic masses, and an additional pair of ventral ganglia connected to pedal ganglia, interpreted as odontophore ganglia. These features are discussed in light of the knowledge of other streptaxids and adaptations to carnivory.

  19. Introduced mammalian predators induce behavioural changes in parental care in an endemic New Zealand bird

    Science.gov (United States)

    Massaro, M.; Starling-Windhof, A.; Briskie, J.V.; Martin, T.E.

    2008-01-01

    The introduction of predatory mammals to oceanic islands has led to the extension of many birds. Although introduced predators should favour changes that reduce predation risk in surviving bird species, the ability of island birds to respond to such novel changes remains unstudied. We tested whether novel predation risk imposed by introduced mammalian predators has altered the parental behaviour of the endemic New Zealand bellbird (Anthomis melanura). We examined parental behaviour of billbnirds at three woodlands sites in New Zealand that differed in predation risk: 1) a mainland site with exotic predators present (high predation risk), 2) a mainland site with exotic predators experimentally removed (low risk recently) and, 3) an off-shore island where exotic predators were never introduced (low risk always). We also compared parental behavior of bellbirds with two closely related Tasmanian honeyeaters (Phylidonyris spp) that evolved with native nest predators (high risk always). Increased nest predation risk has been postulated to favour reduced parental activity, and we tested whether island bellbirds responded to variation in predation risk. We found that females spent more time on the nest per incubating bout with increased risk of predation, a strategy that minimised activity at the nest during incubation. Parental activity during the nestling period, measured as number of feeding visits/hr, also decreased with increasing nest predation risk across sites, and was lowest among the honeyeaters in Tasmania that evolved with native predators. These results demonstrates that some island birds are able to respond to increased risk of predation by novel predators in ways that appear adaptive. We suggest that conservation efforts may be more effective if they take advantage of the ability of island birds to respond to novel predators, especially when the elimination of exotic predators is not possible.

  20. Fish Predation by Semi-Aquatic Spiders: A Global Pattern

    Science.gov (United States)

    Nyffeler, Martin; Pusey, Bradley J.

    2014-01-01

    More than 80 incidences of fish predation by semi-aquatic spiders – observed at the fringes of shallow freshwater streams, rivers, lakes, ponds, swamps, and fens – are reviewed. We provide evidence that fish predation by semi-aquatic spiders is geographically widespread, occurring on all continents except Antarctica. Fish predation by spiders appears to be more common in warmer areas between 40° S and 40° N. The fish captured by spiders, usually ranging from 2–6 cm in length, are among the most common fish taxa occurring in their respective geographic area (e.g., mosquitofish [Gambusia spp.] in the southeastern USA, fish of the order Characiformes in the Neotropics, killifish [Aphyosemion spp.] in Central and West Africa, as well as Australian native fish of the genera Galaxias, Melanotaenia, and Pseudomugil). Naturally occurring fish predation has been witnessed in more than a dozen spider species from the superfamily Lycosoidea (families Pisauridae, Trechaleidae, and Lycosidae), in two species of the superfamily Ctenoidea (family Ctenidae), and in one species of the superfamily Corinnoidea (family Liocranidae). The majority of reports on fish predation by spiders referred to pisaurid spiders of the genera Dolomedes and Nilus (>75% of observed incidences). There is laboratory evidence that spiders from several more families (e.g., the water spider Argyroneta aquatica [Cybaeidae], the intertidal spider Desis marina [Desidae], and the ‘swimming’ huntsman spider Heteropoda natans [Sparassidae]) predate fish as well. Our finding of such a large diversity of spider families being engaged in fish predation is novel. Semi-aquatic spiders captured fish whose body length exceeded the spiders’ body length (the captured fish being, on average, 2.2 times as long as the spiders). Evidence suggests that fish prey might be an occasional prey item of substantial nutritional importance. PMID:24940885

  1. Larval predation on different instars in blowfly populations

    Directory of Open Access Journals (Sweden)

    Lucas Del Bianco Faria

    2004-11-01

    Full Text Available During its larval stage, Chrysomya albiceps (Diptera: Calliphoridae is a facultative predator on other blowflies. In this study, we evaluated the predation by third instar larvae of C. albiceps on first, second and third instar larvae of Chrysomya megacephala and Cochliomyia macellaria in no-choice experiments in order to compare the vulnerability of larval instars to predation. With first and second instar prey the highest predation rate by C. albiceps was on C. megacephala. For third instar prey, the highest predation rate was on C. macellaria. With second instar prey, there was complete predation on C. megacephala within 90 min, whereas in C. macellaria only 55% of the larvae were eaten by 90 min. For third instar prey most predation on C. macellaria (80% occurred within 90 min, whereas in C. megacephala only 35% of the larvae were eaten by 90 min. Chrysomya albiceps changes the predatory behavior on its preys depending on which instar and species it will consume.Chrysomya albiceps (Diptera: Calliphoridae é uma predadora facultativa sobre outras moscas-varejeiras, durante o terceiro instar larval. Nesse estudo, nos investigamos a taxa de predação de C. albiceps sobre larvas de primeiro, segundo e terceiro instar de C. megacephala e C. macellaria comparando a vulnerabilidade dos instares larvais frente à predadora. Para as presas de primeiro e segundo instar, C. albiceps apresentou maior taxa de predação sobre C. megacephala. Já sobre larvas de terceiro instar a predadora consumiu mais C. macellaria. O comportamento de C. albiceps sobre as duas espécies de presas sugere uma mudança na estratégia de forrageio da predadora e essa mudança pode ter influencia sobre a comunidade de dípteros necrófagos.

  2. Fish predation by semi-aquatic spiders: a global pattern.

    Directory of Open Access Journals (Sweden)

    Martin Nyffeler

    Full Text Available More than 80 incidences of fish predation by semi-aquatic spiders--observed at the fringes of shallow freshwater streams, rivers, lakes, ponds, swamps, and fens--are reviewed. We provide evidence that fish predation by semi-aquatic spiders is geographically widespread, occurring on all continents except Antarctica. Fish predation by spiders appears to be more common in warmer areas between 40° S and 40° N. The fish captured by spiders, usually ranging from 2-6 cm in length, are among the most common fish taxa occurring in their respective geographic area (e.g., mosquitofish [Gambusia spp.] in the southeastern USA, fish of the order Characiformes in the Neotropics, killifish [Aphyosemion spp.] in Central and West Africa, as well as Australian native fish of the genera Galaxias, Melanotaenia, and Pseudomugil. Naturally occurring fish predation has been witnessed in more than a dozen spider species from the superfamily Lycosoidea (families Pisauridae, Trechaleidae, and Lycosidae, in two species of the superfamily Ctenoidea (family Ctenidae, and in one species of the superfamily Corinnoidea (family Liocranidae. The majority of reports on fish predation by spiders referred to pisaurid spiders of the genera Dolomedes and Nilus (>75% of observed incidences. There is laboratory evidence that spiders from several more families (e.g., the water spider Argyroneta aquatica [Cybaeidae], the intertidal spider Desis marina [Desidae], and the 'swimming' huntsman spider Heteropoda natans [Sparassidae] predate fish as well. Our finding of such a large diversity of spider families being engaged in fish predation is novel. Semi-aquatic spiders captured fish whose body length exceeded the spiders' body length (the captured fish being, on average, 2.2 times as long as the spiders. Evidence suggests that fish prey might be an occasional prey item of substantial nutritional importance.

  3. A non-diatom plankton bloom controlled by copepod grazing and amphipod predation: Preliminary results from the LOHAFEX iron-fertilisation experiment

    Digital Repository Service at National Institute of Oceanography (India)

    Mazzocchi, M.G.; Gonzalez, H.E.; Vandromme, P.; Borrione, I.; deAlcala, M.R.; Gauns, M.; Assmy, P.; Fuchs, B.; Klaas, C.; Martin, P.; Montresor, M.; Ramaiah, N.; Naqvi, S.W.A.; Smetacek, V.

    INTERNATIONAL NEWSLETTER OCTOBER 2009 3 GLOBEC INTERNATIONAL NEWSLETTER OCTOBER 2009 A non-diatom plankton bloom controlled by copepod grazing and amphipod predation: Preliminary results from the LOHAFEX iron-fertilisation experiment Maria Grazia Mazzocchi 1... and corroborated with counts made with an inverted microscope as high as > 15 x 10 6 cells L - 1 . A significant fraction of the larger flagellates (~ 5 µm) were Phaeocystis solitary cells that started making numerous colonies in the second week, so we were...

  4. Report on the Predation Index, Predator Control Fisheries, and Program Evaluation for the Columbia River Basin Experimental Northern Pikeminnow Management Program, 2008 Annual Report.

    Energy Technology Data Exchange (ETDEWEB)

    Porter, Russell [Pacific States Marine Fisheries Commission].

    2009-09-10

    This report presents results for year seventeen in the basin-wide Experimental Northern Pikeminnow Management Program to harvest northern pikeminnow1 (Ptychocheilus oregonensis) in the Columbia and Snake Rivers. This program was started in an effort to reduce predation by northern pikeminnow on juvenile salmonids during their emigration from natal streams to the ocean. Earlier work in the Columbia River Basin suggested predation by northern pikeminnow on juvenile salmonids might account for most of the 10-20% mortality juvenile salmonids experience in each of eight Columbia River and Snake River reservoirs. Modeling simulations based on work in John Day Reservoir from 1982 through 1988 indicated that, if predator-size northern pikeminnow were exploited at a 10-20% rate, the resulting restructuring of their population could reduce their predation on juvenile salmonids by 50%. To test this hypothesis, we implemented a sport-reward angling fishery and a commercial longline fishery in the John Day Pool in 1990. We also conducted an angling fishery in areas inaccessible to the public at four dams on the mainstem Columbia River and at Ice Harbor Dam on the Snake River. Based on the success of these limited efforts, we implemented three test fisheries on a system-wide scale in 1991 - a tribal longline fishery above Bonneville Dam, a sport-reward fishery, and a dam-angling fishery. Low catch of target fish and high cost of implementation resulted in discontinuation of the tribal longline fishery. However, the sport-reward and dam-angling fisheries were continued in 1992 and 1993. In 1992, we investigated the feasibility of implementing a commercial longline fishery in the Columbia River below Bonneville Dam and found that implementation of this fishery was also infeasible. Estimates of combined annual exploitation rates resulting from the sport-reward and dam-angling fisheries remained at the low end of our target range of 10-20%. This suggested the need for additional

  5. Begin and start: aspect and complement choice

    Directory of Open Access Journals (Sweden)

    Tünde Nagy

    2008-01-01

    Full Text Available The paper offers a semantic analysis of begin and start and their non-finite complementation: the to-infinitive and –ing constructions. The core idea of the paper is that the aspectual constructions ‘begin+ to infinitive’, ‘begin + ing’, ‘start+ to infinitive’, and ‘start+ ing’ have both a schematic and a prototypical meaning, and that the subtle differences between them are motivated by several factors, like viewing (perfectivity vs. imperfectivity, temporality (future orientation vs. ongoing reading dynamicity (graduality vs. abruptness, agentivity, etc.

  6. Effects of an infectious fungus, Batrachochytrium dendrobatidis, on amphibian predator-prey interactions.

    Directory of Open Access Journals (Sweden)

    Barbara A Han

    Full Text Available The effects of parasites and pathogens on host behaviors may be particularly important in predator-prey contexts, since few animal behaviors are more crucial for ensuring immediate survival than the avoidance of lethal predators in nature. We examined the effects of an emerging fungal pathogen of amphibians, Batrachochytrium dendrobatidis, on anti-predator behaviors of tadpoles of four frog species. We also investigated whether amphibian predators consumed infected prey, and whether B. dendrobatidis caused differences in predation rates among prey in laboratory feeding trials. We found differences in anti-predator behaviors among larvae of four amphibian species, and show that infected tadpoles of one species (Anaxyrus boreas were more active and sought refuge more frequently when exposed to predator chemical cues. Salamander predators consumed infected and uninfected tadpoles of three other prey species at similar rates in feeding trials, and predation risk among prey was unaffected by B. dendrobatidis. Collectively, our results show that even sub-lethal exposure to B. dendrobatidis can alter fundamental anti-predator behaviors in some amphibian prey species, and suggest the unexplored possibility that indiscriminate predation between infected and uninfected prey (i.e., non-selective predation could increase the prevalence of this widely distributed pathogen in amphibian populations. Because one of the most prominent types of predators in many amphibian systems is salamanders, and because salamanders are susceptible to B. dendrobatidis, our work suggests the importance of considering host susceptibility and behavioral changes that could arise from infection in both predators and prey.

  7. Effects of an infectious fungus, Batrachochytrium dendrobatidis, on amphibian predator-prey interactions.

    Science.gov (United States)

    Han, Barbara A; Searle, Catherine L; Blaustein, Andrew R

    2011-02-02

    The effects of parasites and pathogens on host behaviors may be particularly important in predator-prey contexts, since few animal behaviors are more crucial for ensuring immediate survival than the avoidance of lethal predators in nature. We examined the effects of an emerging fungal pathogen of amphibians, Batrachochytrium dendrobatidis, on anti-predator behaviors of tadpoles of four frog species. We also investigated whether amphibian predators consumed infected prey, and whether B. dendrobatidis caused differences in predation rates among prey in laboratory feeding trials. We found differences in anti-predator behaviors among larvae of four amphibian species, and show that infected tadpoles of one species (Anaxyrus boreas) were more active and sought refuge more frequently when exposed to predator chemical cues. Salamander predators consumed infected and uninfected tadpoles of three other prey species at similar rates in feeding trials, and predation risk among prey was unaffected by B. dendrobatidis. Collectively, our results show that even sub-lethal exposure to B. dendrobatidis can alter fundamental anti-predator behaviors in some amphibian prey species, and suggest the unexplored possibility that indiscriminate predation between infected and uninfected prey (i.e., non-selective predation) could increase the prevalence of this widely distributed pathogen in amphibian populations. Because one of the most prominent types of predators in many amphibian systems is salamanders, and because salamanders are susceptible to B. dendrobatidis, our work suggests the importance of considering host susceptibility and behavioral changes that could arise from infection in both predators and prey.

  8. A Healthy Start Can Begin Now

    Science.gov (United States)

    A healthy pregnancy begins before you ever become pregnant. Give yourself the best chance for a healthy pregnancy and healthy baby before you start down the road to motherhood. If you smoke, now’s a great time to quit.

  9. Drug Abuse Prevention Starts with Parents

    Science.gov (United States)

    ... Stages Prenatal Baby Toddler Preschool Gradeschool Teen Dating & Sex Fitness Nutrition Driving Safety School Substance Use Young Adult Healthy Children > Ages & Stages > Teen > Substance Use > Drug Abuse Prevention Starts with Parents Ages & Stages Listen Español ...

  10. Start small and build toward business intelligence.

    Science.gov (United States)

    Kirby, Sean; Robertson, Brian

    2009-01-01

    To use business intelligence effectively, healthcare organizations should start small, align organizationally, and leverage success. Organizations should determine which measures they need and how to present them. Organizations should reinvest savings to continually improve.

  11. Increased control of thrips and aphids in greenhouses with two species of generalist predatory bugs involved in intraguild predation

    NARCIS (Netherlands)

    Messelink, G.J.; Janssen, A.

    2014-01-01

    The combined release of species of generalist predators can enhance multiple pest control when the predators feed on different prey, but, in theory, predators may be excluded through predation on each other. This study evaluated the co-occurrence of the generalist predators Macrolophus pygmaeus

  12. Predation by Red Foxes (Vulpes vulpes at an Outdoor Piggery

    Directory of Open Access Journals (Sweden)

    Patricia A. Fleming

    2016-10-01

    Full Text Available Outdoor pig operations are an alternative to intensive systems of raising pigs; however for the majority of outdoor pork producers, issues of biosecurity and predation control require significant management and (or capital investment. Identifying and quantifying predation risk in outdoor pork operations has rarely been done, but such data would be informative for these producers as part of their financial and logistical planning. We quantified potential impact of fox predation on piglets bred on an outdoor pork operation in south-western Australia. We used remote sensor cameras at select sites across the farm as well as above farrowing huts to record interactions between predators and pigs (sows and piglets. We also identified animal losses from breeding records, calculating weaning rate as a proportion of piglets born. Although only few piglets were recorded lost to fox predation (recorded by piggery staff as carcasses that are “chewed”, it is likely that foxes were contributing substantially to the 20% of piglets that were reported “missing”. Both sets of cameras recorded a high incidence of fox activity; foxes appeared on camera soon after staff left for the day, were observed tracking and taking live piglets (despite the presence of sows, and removed dead carcasses from in front of the cameras. Newly born and younger piglets appeared to be the most vulnerable, especially when they are born out in the paddock, but older piglets were also lost. A significant ( p = 0.001 effect of individual sow identification on the weaning rate, but no effect of sow age (parity, suggests that individual sow behavior towards predators influences predation risk for litters. We tracked the movement of piglet carcasses by foxes, and confirmed that foxes make use of patches of native vegetation for cover, although there was no effect of paddock, distance to vegetation, or position on the farm on weaning rate. Trials with non-toxic baits reveal high levels

  13. Predation by Red Foxes (Vulpes vulpes) at an Outdoor Piggery.

    Science.gov (United States)

    Fleming, Patricia A; Dundas, Shannon J; Lau, Yvonne Y W; Pluske, John R

    2016-10-08

    Outdoor pig operations are an alternative to intensive systems of raising pigs; however for the majority of outdoor pork producers, issues of biosecurity and predation control require significant management and (or) capital investment. Identifying and quantifying predation risk in outdoor pork operations has rarely been done, but such data would be informative for these producers as part of their financial and logistical planning. We quantified potential impact of fox predation on piglets bred on an outdoor pork operation in south-western Australia. We used remote sensor cameras at select sites across the farm as well as above farrowing huts to record interactions between predators and pigs (sows and piglets). We also identified animal losses from breeding records, calculating weaning rate as a proportion of piglets born. Although only few piglets were recorded lost to fox predation (recorded by piggery staff as carcasses that are "chewed"), it is likely that foxes were contributing substantially to the 20% of piglets that were reported "missing". Both sets of cameras recorded a high incidence of fox activity; foxes appeared on camera soon after staff left for the day, were observed tracking and taking live piglets (despite the presence of sows), and removed dead carcasses from in front of the cameras. Newly born and younger piglets appeared to be the most vulnerable, especially when they are born out in the paddock, but older piglets were also lost. A significant ( p = 0.001) effect of individual sow identification on the weaning rate, but no effect of sow age (parity), suggests that individual sow behavior towards predators influences predation risk for litters. We tracked the movement of piglet carcasses by foxes, and confirmed that foxes make use of patches of native vegetation for cover, although there was no effect of paddock, distance to vegetation, or position on the farm on weaning rate. Trials with non-toxic baits reveal high levels of non-target bait

  14. Predation, Competition, and Abiotic Disturbance: Population Dynamics of Small Mammals

    Energy Technology Data Exchange (ETDEWEB)

    Yunger, John A.; /Northern Illinois U. /Northern Illinois U.

    1996-01-01

    Predation and food availability have been implicated in annual non-cyclic fluctuations of vertebrate prey at mid-latitudes. The timing and magnitude of these factors are unclear due to a lack of large-scale field experiments, little attention to interactions, and a failure to closely link vertebrate predators with their prey. From October 1992 to January 1996, small mammal populations were censused on eight 0.6 ha plots at monthly intervals in a 32-ha prairie restoration at Fermi National Accelerator Laboratory, Illinois. Terrestrial vertebrate predators were excluded after July 1993 from four of the eight plots and canid diets monitored. Both terrestrial and avian vertebrate predators were excluded in March 1994. During 1993 small mammal densities (i.e., Microtus Pennsylvanicus, Peromyscus leucopus, and P. maniculatus) were relatively high. Following peak densities in late summer, Microtus numbers wer 2-3x greater on exclusion plots relative to controls due to preferential selection of Microtus by canids, as reflected in dits. Following an ice-storm and crash in small mammal numbers (particularly Microtus), vertebrate predator exclusion had no detectable effect on P. leucopus numbers, probably due to an abundance of alternative prey (i.e., Sylvilagus floridanus). Meadow vole numbers began to increase in Fall 1995, and a numerical effect of predator exclusion, similar to that in 1993, was observed. Predator exclusion had no detectable effect on the movements and spatial patterns of Microtus during 1993. There was a significant decrease in home range and a significant increase in home range overlap for P. leucopus on the predator exclusion plots. The change in spatial behavior may be due to interspecific competition with Microtus resulting from increased densities on exclusion plots. Thus, predators had an indirect effect on P. leucopus spatial patterns mediated through M. Pennsylvanicus. The role of food limitation was studied using natural and manipulative

  15. Predation, Competition, and Abiotic Disturbance: Population Dynamics of Small Mammals

    Energy Technology Data Exchange (ETDEWEB)

    Yunger, John A. [Northern Illinois U.

    1996-01-01

    Predation and food availability have been implicated in annual non-cyclic fluctuations of vertebrate prey at mid-latitudes. The timing and magnitude of these factors are unclear due to a lack of large-scale field experiments, little attention to interactions, and a failure to closely link vertebrate predators with their prey. From October 1992 to January 1996, small mammal populations were censused on eight 0.6 ha plots at monthly intervals in a 32-ha prairie restoration at Fermi National Accelerator Laboratory, Illinois. Terrestrial vertebrate predators were excluded after July 1993 from four of the eight plots and canid diets monitored. Both terrestrial and avian vertebrate predators were excluded in March 1994. During 1993 small mammal densities (i.e., Microtus pennsylvanicus, Peromyscus leucopus, and P. maniculatus) were relatively high. Following peak densities in late summer, Microtus numbers were 2-3x greater on exclusion plots relative to controls due to preferential selection of Microtus by canids, as reflected in diets. Following an ice-storm and crash in small mammal numbers (particularly Microtus), vertebrate predator exclusion had no detectable effect on P. leucopus numbers, probably due to an abundance of alternative prey (i.e., Sylvilagus floridanus). Meadow vole numbers began to increase in Fall 1995, and a numerical effect of predator exclusion, similar to that in 1993, was observed. Predator exclusion had no detectable effect on the movements and spatial patterns of Microtus during 1993. There was a significant decrease in home range and a significant increase in home range overlap for £.. leucopus on the predator exclusion plots. The change in spatial behavior may be due to interspecific competition with Microtus resulting from increased densities on exclusion plots. Thus, predators had an indirect effect on .f.. leucopus spatial patterns mediated through M. pennsylvanicus. The role of food limitation was studied using natural and manipulative

  16. Predator facilitation or interference: a game of vipers and owls.

    Science.gov (United States)

    Embar, Keren; Raveh, Ashael; Hoffmann, Ishai; Kotler, Burt P

    2014-04-01

    In predator-prey foraging games, the prey's reaction to one type of predator may either facilitate or hinder the success of another predator. We ask, do different predator species affect each other's patch selection? If the predators facilitate each other, they should prefer to hunt in the same patch; if they interfere, they should prefer to hunt alone. We performed an experiment in a large outdoor vivarium where we presented barn owls (Tyto alba) with a choice of hunting greater Egyptian gerbils (Gerbillus pyramidum) in patches with or without Saharan horned vipers (Cerastes cerastes). Gerbils foraged on feeding trays set under bushes or in the open. We monitored owl location, activity, and hunting attempts, viper activity and ambush site location, and the foraging behavior of the gerbils in bush and open microhabitats. Owls directed more attacks towards patches with vipers, and vipers were more active in the presence of owls. Owls and vipers facilitated each other's hunting through their combined effect on gerbil behavior, especially on full moon nights when vipers are more active. Owls forced gerbils into the bushes where vipers preferred to ambush, while viper presence chased gerbils into the open where they were exposed to owls. Owls and vipers took advantage of their indirect positive effect on each other. In the foraging game context, they improve each other's patch quality and hunting success.

  17. Predation rate by wolves on the Porcupine caribou herd

    Directory of Open Access Journals (Sweden)

    Robert D. Hayes

    2000-04-01

    Full Text Available Large migratory catibou {Rangifer tarandus herds in the Arctic tend to be cyclic, and population trends are mainly driven by changes in forage or weather events, not by predation. We estimated daily kill rate by wolves on adult caribou in winter, then constructed a time and space dependent model to estimate annual wolf (Canis lupus predation rate (P annual on adult Porcupine caribou. Our model adjusts predation seasonally depending on caribou distribution: Pannual = SIGMAdaily* W *Ap(2*Dp. In our model we assumed that wolves killed adult caribou at a constant rate (Kdaily, 0.08 caribou wolf1 day1 based on our studies and elsewhere; that wolf density (W doubled to 6 wolves 1000 km2-1 on all seasonal ranges; and that the average area occupied by the Porcupine caribou herd (PCH in eight seasonal life cycle periods (Dp was two times gteater than the area described by the outer boundaries of telemetry data (Ap /1000 km2. Results from our model projected that wolves kill about 7600 adult caribou each year, regardless of herd size. The model estimated that wolves removed 5.8 to 7.4% of adult caribou as the herd declined in the 1990s. Our predation rate model supports the hypothesis of Bergerud that spacing away by caribou is an effective anti-predatory strategy that greatly reduces wolf predation on adult caribou in the spring and summer.

  18. Hydrodynamic effects on a predator approaching a group of preys

    Science.gov (United States)

    De Rosis, Alessandro

    2014-11-01

    A numerical approach to predict the hydrodynamics involving a predator approaching a group of 100 preys is presented. A collective behavioural model is adopted to predict the two-dimensional space-time evolution of the predator-preys system that is supposed to be immersed in a fluid. The preys manifest mutual repulsion, attraction and orientation, while the predator is idealized as an individual to be strongly repulsed. During the motion, the predator experiences a resistance induced by the encompassing fluid. Such effect is accounted for by computing the hydrodynamic force and by modifying the predator’s velocity given by the behavioural equations. A numerical campaign is carried out by varying the predator’s drag coefficient. Moreover, analyses characterized by progressively wider predator’s perception areas are performed, thus highlighting the role of the hydrodynamics over the behavioural interactions. In order to estimate the predator’s performance, an ad-hoc parameter is proposed. Moreover, findings in terms of trajectories and angular momentum of the group of preys are discussed. Present findings show that the sole collective behavioural equations are insufficient to predict the performance of a predator that is immersed in a fluid, since its motion is drastically affected by the resistance of the surrounding fluid.

  19. Predator Perspective Drives Geographic Variation in Frequency-Dependent Polymorphism.

    Science.gov (United States)

    Holmes, Iris A; Grundler, Maggie R; Davis Rabosky, Alison R

    2017-10-01

    Color polymorphism in natural populations can manifest as a striking patchwork of phenotypes in space, with neighboring populations characterized by dramatic differences in morph composition. These geographic mosaics can be challenging to explain in the absence of localized selection because they are unlikely to result from simple isolation-by-distance or clinal variation in selective regimes. To identify processes that can lead to the formation of geographic mosaics, we developed a simulation-based model to explore the influence of predator perspective, selection, migration, and genetic linkage of color loci on allele frequencies in polymorphic populations over space and time. Using simulated populations inspired by the biology of Heliconius longwing butterflies, Cepaea land snails, Oophaga poison frogs, and Sonora ground snakes, we found that the relative sizes of predator and prey home ranges can produce large differences in morph composition between neighboring populations under both positive and negative frequency-dependent selection. We also demonstrated the importance of the interaction of predator perspective with the type of frequency dependence and localized directional selection across migration and selection intensities. Our results show that regional-scale predation can promote the formation of phenotypic mosaics in prey species, without the need to invoke spatial variation in selective regimes. We suggest that predator behavior can play an important and underappreciated role in the formation and maintenance of geographic mosaics in polymorphic species.

  20. Effects of predation by Hydra (Cnidaria on cladocerans (Crustacea: Cladocera

    Directory of Open Access Journals (Sweden)

    Ligia Rivera-De la Parra

    2016-03-01

    Full Text Available Planktonic cladocerans have evolved different strategies to avoid predation from vertebrates; these include changes in morphology, behavior, physiology, and/or life-history traits. However, littoral cladocerans are better adapted to avoid invertebrate predation particularly from insect larvae by evolving morphological and physiological adaptations. Nevertheless, this has not been proven for some littoral predators such as Hydra. In this study, we provide quantitative data on how Hydra affects its zooplankton prey. We studied the predation behavior on Alona glabra, Ceridodaphnia dubia, Daphnia pulex, Daphnia cf. mendotae, Diaphanosoma birgei, Macrothrix triserialis, Moina macrocopa, Pleuroxus aduncus, Scapholeberis kingi, Simocephalus vetulus, Elaphoidella grandidieri, Brachionus rubens and Euchlanis dilatata. We also tested the indirect effect of allelochemicals from Hydra on the demography of Daphnia cf. mendotae. Littoral cladocerans are specially adapted to resist nematocyst injection and discharge of toxic substances from Hydra. A significant decrease in the population growth rate from 0.21 to 0.125 d-1 was observed at densities of 2 ind. ml-1. The role of carapace thickness as an adaptive strategy of littoral cladocerans against Hydra predation is discussed.

  1. Indirect evolutionary rescue: prey adapts, predator avoids extinction

    Science.gov (United States)

    Yamamichi, Masato; Miner, Brooks E

    2015-01-01

    Recent studies have increasingly recognized evolutionary rescue (adaptive evolution that prevents extinction following environmental change) as an important process in evolutionary biology and conservation science. Researchers have concentrated on single species living in isolation, but populations in nature exist within communities of interacting species, so evolutionary rescue should also be investigated in a multispecies context. We argue that the persistence or extinction of a focal species can be determined solely by evolutionary change in an interacting species. We demonstrate that prey adaptive evolution can prevent predator extinction in two-species predator–prey models, and we derive the conditions under which this indirect evolutionary interaction is essential to prevent extinction following environmental change. A nonevolving predator can be rescued from extinction by adaptive evolution of its prey due to a trade-off for the prey between defense against predation and population growth rate. As prey typically have larger populations and shorter generations than their predators, prey evolution can be rapid and have profound effects on predator population dynamics. We suggest that this process, which we term ‘indirect evolutionary rescue’, has the potential to be critically important to the ecological and evolutionary responses of populations and communities to dramatic environmental change. PMID:26366196

  2. Bagworm bags as portable armour against invertebrate predators

    Directory of Open Access Journals (Sweden)

    Shinji Sugiura

    2016-02-01

    Full Text Available Some animals have evolved the use of environmental materials as “portable armour” against natural enemies. Portable bags that bagworm larvae (Lepidoptera: Psychidae construct using their own silk and plant parts are generally believed to play an important role as a physical barrier against natural enemies. However, no experimental studies have tested the importance of bags as portable armour against predators. To clarify the defensive function, I studied the bagworm Eumeta minuscula and a potential predator Calosoma maximoviczi (Coleoptera: Carabidae. Under laboratory conditions, all bagworm larvae were attacked by carabid adults, but successfully defended themselves against the predators’ mandibles using their own bags. The portable bags, which are composed mainly of host plant twigs, may function as a physical barrier against predator mandibles. To test this hypothesis, I removed the twig bags and replaced some with herb leaf bags; all bag-removed larvae were easily caught and predated by carabids, while all bag-replaced larvae could successfully defend themselves against carabid attacks. Therefore, various types of portable bags can protect bagworm larvae from carabid attacks. This is the first study to test the defensive function of bagworm portable bags against invertebrate predators.

  3. Body size matters for aposematic prey during predator aversion learning.

    Science.gov (United States)

    Smith, Karen E; Halpin, Christina G; Rowe, Candy

    2014-11-01

    Aposematic prey advertise their toxicity to predators using conspicuous warning signals, which predators learn to use to reduce their intake of toxic prey. Like other types of prey, aposematic prey often differ in body size, both within and between species. Increasing body size can increase signal size, which make larger aposematic prey more detectable but also gives them a more effective and salient deterrent. However, increasing body size also increases the nutritional value of prey, and larger aposematic prey may make a more profitable meal to predators that are trading off the costs of eating toxins with the benefits of ingesting nutrients. We tested if body size, independent of signal size, affected predation of toxic prey as predators learn to reduce their attacks on them. European starlings (Sturnus vulgaris) learned to discriminate between defended (quinine-injected) and undefended (water-injected) mealworm prey (Tenebrio molitor) using visual signals. During this process, we found that birds attacked and ate more defended prey the larger they were. Body size does affect the probability that toxic prey are attacked and eaten, which has implications for the evolutionary dynamics of aposematism and mimicry (where species share the same warning pattern). Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

  4. Increased predation of nutrient-enriched aposematic prey.

    Science.gov (United States)

    Halpin, Christina G; Skelhorn, John; Rowe, Candy

    2014-04-22

    Avian predators readily learn to associate the warning coloration of aposematic prey with the toxic effects of ingesting them, but they do not necessarily exclude aposematic prey from their diets. By eating aposematic prey 'educated' predators are thought to be trading-off the benefits of gaining nutrients with the costs of eating toxins. However, while we know that the toxin content of aposematic prey affects the foraging decisions made by avian predators, the extent to which the nutritional content of toxic prey affects predators' decisions to eat them remains to be tested. Here, we show that European starlings (Sturnus vulgaris) increase their intake of a toxic prey type when the nutritional content is artificially increased, and decrease their intake when nutritional enrichment is ceased. This clearly demonstrates that birds can detect the nutritional content of toxic prey by post-ingestive feedback, and use this information in their foraging decisions, raising new perspectives on the evolution of prey defences. Nutritional differences between individuals could result in equally toxic prey being unequally predated, and might explain why some species undergo ontogenetic shifts in defence strategies. Furthermore, the nutritional value of prey will likely have a significant impact on the evolutionary dynamics of mimicry systems.

  5. Predator Persistence through Variability of Resource Productivity in Tritrophic Systems.

    Science.gov (United States)

    Soudijn, Floor H; de Roos, André M

    2017-12-01

    The trophic structure of species communities depends on the energy transfer between trophic levels. Primary productivity varies strongly through time, challenging the persistence of species at higher trophic levels. Yet resource variability has mostly been studied in systems with only one or two trophic levels. We test the effect of variability in resource productivity in a tritrophic model system including a resource, a size-structured consumer, and a size-specific predator. The model complies with fundamental principles of mass conservation and the body-size dependence of individual-level energetics and predator-prey interactions. Surprisingly, we find that resource variability may promote predator persistence. The positive effect of variability on the predator arises through periods with starvation mortality of juvenile prey, which reduces the intraspecific competition in the prey population. With increasing variability in productivity and starvation mortality in the juvenile prey, the prey availability increases in the size range preferred by the predator. The positive effect of prey mortality on the trophic transfer efficiency depends on the biologically realistic consideration of body size-dependent and food-dependent functions for growth and reproduction in our model. Our findings show that variability may promote the trophic transfer efficiency, indicating that environmental variability may sustain species at higher trophic levels in natural ecosystems.

  6. Guppies as predators of common mosquito larvae in Malaysia.

    Science.gov (United States)

    Saleeza, S N R; Norma-Rashid, Y; Sofian-Azirun, M

    2014-03-01

    Observation on predation activities of guppies (Poecilia reticulata) on the larvae of three species of mosquito, namely Aedes albopictus, Aedes aegypti, and Culex quinquefasciatus was carried out under laboratory conditions. Male and female guppies were used as predators for predation experiments on the 4th instars of mosquito larvae. The daily feeding rates comparing male and female guppies on mosquito larvae were different; the female guppies consumed more mosquito larvae than male guppies did. The daily feeding rates of female guppies were 121.3 for Ae. aegypti, 105.6 for Ae. albopictus, and 72.3 for Cx. quinquefasciatus. The daily feeding rates of male guppies were 98.6 for Ae. aegypti, 73.6 for Ae. albopictus, and 47.6 for Cx. quinquefasciatus. In terms of prey preference, there was greater preference towards mosquito larvae of Ae. aegypti, followed by Ae. albopictus, and the least preferred was Cx. quinquefasciatus. Male and female guppies consumed more mosquito larvae during lights on (day time) compared with lights off (night time). The water volume, prey species, number of fish predators available, prey densities, and prey's sex also influenced the predation activities.

  7. Attracting predators without falling prey: chemical camouflage protects honeydew-producing treehoppers from ant predation.

    Science.gov (United States)

    Silveira, Henrique C P; Oliveira, Paulo S; Trigo, José R

    2010-02-01

    Predaceous ants are dominant organisms on foliage and represent a constant threat to herbivorous insects. The honeydew of sap-feeding hemipterans has been suggested to appease aggressive ants, which then begin tending activities. Here, we manipulated the cuticular chemical profiles of freeze-dried insect prey to show that chemical background matching with the host plant protects Guayaquila xiphias treehoppers against predaceous Camponotus crassus ants, regardless of honeydew supply. Ant predation is increased when treehoppers are transferred to a nonhost plant with which they have low chemical similarity. Palatable moth larvae manipulated to match the chemical background of Guayaquila's host plant attracted lower numbers of predatory ants than unchanged controls. Although aggressive tending ants can protect honeydew-producing hemipterans from natural enemies, they may prey on the trophobionts under shortage of alternative food resources. Thus chemical camouflage in G. xiphias allows the trophobiont to attract predaceous bodyguards at reduced risk of falling prey itself.

  8. Parasitised caterpillars suffer reduced predation: potential implications for intra-guild predation.

    Science.gov (United States)

    Chen, Wen-Bin; Vasseur, Liette; You, Min-Sheng; Li, Jian-Yu; Wang, Cheng-Xiang; Meng, Ruo-Xue; Gurr, Geoff M

    2017-02-23

    Intra-guild predation (IGP) is an important phenomenon structuring ecological communities and affects the success of biological control. Here we show that parasitism by the koinobiont wasp Cotesia vestalis is associated with behavioural changes in its larval host (diamondback moth, Plutella xylostella) that reduce risk of IGP. Compared with unparasitised caterpillars, parasitised P. xylostella moved less frequently to new feeding patches on plants and were less likely to fall from the plant. Wolf spiders killed significantly fewer parasitised larvae. Reflecting their reduced movement and capacity to select plant tissue of optimal quality, parasitised caterpillars fed at a lower rate and exhibited delayed development suggesting a trade-off between IGP avoidance and nutrient intake by the host. This change in behaviour to reduce risk may cascade to the first trophic level and help explain the stability of IGP systems.

  9. Biological conservation of a prey-predator system incorporating constant prey refuge through provision of alternative food to predators: a theoretical study.

    Science.gov (United States)

    Chakraborty, Kunal; Das, Sankha Subhra

    2014-06-01

    We describe a prey-predator system incorporating constant prey refuge through provision of alternative food to predators. The proposed model deals with a problem of non-selective harvesting of a prey-predator system in which both the prey and the predator species obey logistic law of growth. The long-run sustainability of an exploited system is discussed through provision of alternative food to predators. We have analyzed the variability of the system in presence of constant prey refuge and examined the stabilizing effect on predator-prey system. The steady states of the system are derived and dynamical behavior of the system is extensively analyzed around steady states. The optimal harvesting policy is formulated and solved with the help of Pontryagin's maximal principle. Our objective is to maximize the monetary social benefit through protecting the predator species from extinction, keeping the ecological balance. Results finally illustrated with the help of numerical examples.

  10. Western Pond Turtle Head-starting and Reintroduction; 2004-2005 Annual Report.

    Energy Technology Data Exchange (ETDEWEB)

    Van Leuven, Susan; Allen, Harriet; Slavin, Kate (Washington Department of Fish and Wildlife, Wildlife Management Program, Olympia, WA)

    2005-09-01

    This report covers the results of the western pond turtle head-starting and reintroduction project for the period of October 2004-September 2005. Wild hatchling western pond turtles from the Columbia River Gorge were reared at the Woodland Park and Oregon Zoos in 2004 and 2005 as part of the recovery effort for this Washington State endangered species. The objective of the program is to reduce losses to introduced predators like bullfrogs and largemouth bass by raising the hatchlings to a size where they are too large to be eaten by most of these predators. Thirty-five turtles were placed at the Woodland Park Zoo and 53 at the Oregon Zoo. Of these, 77 head-started juvenile turtles were released at three sites in the Columbia Gorge in 2005. Four were held back to attain more growth in captivity. Eleven were released at the Klickitat ponds, 22 at the Klickitat lake, 39 at the Skamania site, and 5 at Pierce National Wildlife Refuge (NWR). This brought the total number of head-start turtles released since 1991 to 257 for the Klickitat ponds, 136 for the Klickitat lake, 206 for the Skamania pond complex, and 255 at Pierce NWR. In 2005, 34 females from the two Columbia Gorge populations were equipped with transmitters and monitored for nesting activity. Twenty-four nests were located and protected; these produced 90 hatchlings. The hatchlings were collected in September and transported to the Oregon and Woodland Park zoos for rearing in the head-start program. During the 2005 field season trapping effort, 486 western pond turtles were captured in the Columbia Gorge, including 430 previously head-started turtles. These recaptures, together with confirmed nesting by head-start females and visual resightings, indicate the program is succeeding in boosting juvenile recruitment to increase the populations. Records were also collected on 216 individual painted turtles captured in 2005 during trapping efforts at Pierce NWR, to gather baseline information on this native

  11. Western Pond Turtle Head-starting and Reintroduction, 2005-2006 Annual Report.

    Energy Technology Data Exchange (ETDEWEB)

    Van Leuven, Susan; Allen, Harriet; Slavens, Kate (Washington Department of Fish and Wildlife, Wildlife Management Program, Olympia, WA)

    2006-11-01

    This report covers the results of the western pond turtle head-starting and reintroduction project for the period of October 2005-September 2006. Wild hatchling western pond turtles from the Columbia River Gorge were reared at the Woodland Park and Oregon zoos in 2005 and 2006 as part of the recovery effort for this Washington State endangered species. The objective of the program is to reduce losses to introduced predators like bullfrogs and largemouth bass by raising the hatchlings to a size where they are too large to be eaten by most of these predators. Twenty-six turtles were placed at the Woodland Park Zoo and 62 at the Oregon Zoo in fall 2005. These turtles joined two that were held back from release in summer 2005 due to their small size. All 90 juvenile turtles were released at three sites in the Columbia Gorge in 2006. Twenty-eight juvenile turtles were released at the Klickitat ponds, 22 at the Klickitat lake, 21 at the Skamania site, and 19 at Pierce National Wildlife Refuge (NWR). This brought the total number of head-start turtles released since 1991 to 944; 285 for the Klickitat ponds, 158 for the Klickitat lake, 227 for the Skamania pond complex, and 274 at Pierce NWR. In 2006, 20 females from the Klickitat population were equipped with transmitters and monitored for nesting activity. Fifteen nests were located and protected; these produced 55 hatchlings. The hatchlings were collected in September and transported to the Oregon and Woodland Park zoos for rearing in the head-start program. One wild hatchling captured in spring 2006 was placed in the head-start program to attain more growth in captivity. During the 2006 field season trapping effort, 414 western pond turtles were captured in the Columbia Gorge, including 374 previously head-started turtles. These recaptures, together with confirmed nesting by head-start females and visual resightings, indicate the program is succeeding in boosting juvenile recruitment to increase the populations

  12. Western Pond Turtle Head-starting and Reintroduction; 2003-2004 Annual Report.

    Energy Technology Data Exchange (ETDEWEB)

    Van Leuven, Susan; Allen, Harriet; Slavin, Kate (Washington Department of Fish and Wildlife, Wildlife Management Program, Olympia, WA)

    2004-09-01

    This report covers the results of the western pond turtle head-starting and reintroduction project for the period of October 2003-September 2004. Wild hatchling western pond turtles from the Columbia River Gorge were reared at the Woodland Park and Oregon Zoos in 2003 and 2004 as part of the recovery effort for this Washington State endangered species. The objective of the program is to reduce losses to introduced predators like bullfrogs and largemouth bass by raising the hatchlings to a size where they are too large to be eaten by most of these predators. Sixty-nine turtles were over-wintered at the Woodland Park Zoo and 69 at the Oregon Zoo. Of these, 136 head-started juvenile turtles were released at three sites in the Columbia Gorge in 2004. Two were held back to attain more growth in captivity. Thirty-four were released at the Klickitat ponds, 19 at the Klickitat lake, 21 at the Skamania site, and 62 at Pierce National Wildlife Refuge (NWR). This brought the total number of head-start turtles released since 1991 to 246 for the Klickitat ponds, 114 for the Klickitat lake, 167 for the Skamania pond complex, and 250 at Pierce NWR. In 2004, 32 females from the two Columbia Gorge populations were equipped with transmitters and monitored for nesting activity. Twenty-one of the females nested and produced 85 hatchlings. The hatchlings were collected in September and October and transported to the Woodland Park and Oregon zoos for rearing in the head-start program. Data collection for a four-year telemetry study of survival and habitat use by juvenile western pond turtles at Pierce NWR concluded in 2004. Radio transmitters on study animals were replaced as needed until all replacements were in service; afterward, the turtles were monitored until their transmitters failed. The corps of study turtles ranged from 39 in August 2003 to 2 turtles at the end of August 2004. These turtles showed the same seasonal pattern of movements between summer water and upland winter

  13. Personality-dependent dispersal cancelled under predation risk.

    Science.gov (United States)

    Cote, Julien; Fogarty, Sean; Tymen, Blaise; Sih, Andrew; Brodin, Tomas

    2013-12-22

    Dispersal is a fundamental life-history trait for many ecological processes. Recent studies suggest that dispersers, in comparison to residents, display various phenotypic specializations increasing their dispersal inclination or success. Among them, dispersers are believed to be consistently more bold, exploratory, asocial or aggressive than residents. These links between behavioural types and dispersal should vary with the cause of dispersal. However, with the exception of one study, personality-dependent dispersal has not been studied in contrasting environments. Here, we used mosquitofish (Gambusia affinis) to test whether personality-dependent dispersal varies with predation risk, a factor that should induce boldness or sociability-dependent dispersal. Corroborating previous studies, we found that dispersing mosquitofish are less social than non-dispersing fish when there was no predation risk. However, personality-dependent dispersal is negated under predation risk, dispersers having similar personality types to residents. Our results suggest that adaptive dispersal decisions could commonly depend on interactions between phenotypes and ecological contexts.

  14. Susceptibility of Select Agents to Predation by Predatory Bacteria

    Directory of Open Access Journals (Sweden)

    Riccardo Russo

    2015-12-01

    Full Text Available Select Agents are microorganisms and toxins considered to be exploitable as biological weapons. Although infections by many Select Agents can be treated by conventional antibiotics, the risk of an emerging or engineered drug resistant strain is of great concern. One group of microorganisms that is showing potential to control drug resistant Gram-negative bacteria are the predatory bacteria from the genera Bdellovibrio spp. and Micavibrio spp. In this study, we have examined the ability of Bdellovibrio bacteriovorus (B. bacteriovorus strain 109J, HD100 and Micavibrio aeruginosavorus (M. aeruginosavorus ARL-13 to prey on a variety of Select Agents. Our findings demonstrate that B. bacteriovorus and M. aeruginosavorus are able to prey efficiently on Yersinia pestis and Burkholderia mallei. Modest predation was also measured in co-cultures of B. bacteriovorus and Francisella tularensis. However, neither of the predators showed predation when Burkholderia pseudomallei and Brucella melitensis were used as prey.

  15. Escape of protists in predator-generated feeding currents

    DEFF Research Database (Denmark)

    Jakobsen, Hans Henrik

    2002-01-01

    The ciliate Strobilidium sp. and 2 flagellates, Chrysochromulina simplex and Gymnodinium sp., were exposed to predator-generated feeding currents, and their escape responses were quantified using 2- and 3-dimensional video techniques. All 3 studied organisms responded by escaping at a defined...... distance to their predators. A critical threshold fluid deformation rate of escape of 3.6 s(-1) was estimated in a quantifiable siphon suction flow field for the ciliate Strobilidium sp. Using previous published models and the critical deformation rate estimated here, I predicted the reaction distance...... to the ciliate, the critical deformation for escape for both the flagellates was estimated to range between 6.9 and 14.5 s(-1). The critical deformation rate of flagellates proved to be slightly higher than that of ciliates. I speculate that this reflects that ciliates are the main predator on flagellates while...

  16. Varying predator personalities generates contrasting prey communities in an agroecosystem.

    Science.gov (United States)

    Royauté, Raphaël; Pruitt, Jonathan N

    2015-11-01

    Most taxa show consistent individual differences in behavior, a phenomenon often referred to as animal "personalities." While the links between individual personality and fitness have received considerable attention, little information is available on how animal personality impacts higher-order ecological processes, such as community dynamics. Using a mesocosm experiment, we subjected a representative community of alfalfa pests to different compositions of personality types of the wolf spider Pardosa milvina. We show that subtle variation in the personality composition of P. milvina populations generate wildly different prey communities, where a mixture of both active and sedentary individuals performs best at suppressing prey abundance. Our results provide the first experimental evidence that predator personality types can generate contrasting prey communities. Moreover, our results suggest that manipulating the representation of predator personality types may be a profitable avenue by which one can maximize the biocontrol potential of predator populations.

  17. Intraguild predation influences oviposition behavior of blow flies (Diptera: Calliphoridae).

    Science.gov (United States)

    Galindo, Luciane A; Moral, Rafael A; Moretti, Thiago C; Godoy, Wesley A C; Demétrio, Clarice G B

    2016-05-01

    The objective of the present study was to determine whether blow flies (Diptera: Calliphoridae) are able to identify larvae of an intraguild predator species in the substrate and avoid laying eggs there. Blow flies oviposited in traps with different treatments: substrate only and substrate with larvae of Chrysomya albiceps (Wiedemann, 1819), Chrysomya megacephala (Fabricius, 1794), or Chrysomya putoria (Wiedemann, 1830). Ch. megacephala, Ch. putoria, and Lucilia eximia (Wiedemann, 1819) avoided laying eggs in the trap containing Ch. albiceps larvae. Cochliomyia macellaria (Fabricius, 1775) did not oviposit differently in each substrate but had overall low abundance. The prevalence of species on corpses may be influenced by the ability of the species to detect the presence of other species, mainly predators. In this sense, intraguild predation may result in misinterpretations of a crime scene and should be considered when assessing the minimum postmortem interval.

  18. A single predator charging a herd of prey: effects of self volume and predator-prey decision-making

    CERN Document Server

    Schwarzl, M; Oshanin, G; Metzler, R

    2016-01-01

    We study the degree of success of a single predator hunting a herd of prey on a two dimensional square lattice landscape. We explicitly consider the self volume of the prey restraining their dynamics on the lattice. The movement of both predator and prey is chosen to include an intelligent, decision making step based on their respective sighting ranges, the radius in which they can detect the other species (prey cannot recognise each other besides the self volume interaction): after spotting each other the motion of prey and predator turns from a nearest neighbour random walk into direct escape or chase, respectively. We consider a large range of prey densities and sighting ranges and compute the mean first passage time for a predator to catch a prey as well as characterise the effective dynamics of the hunted prey. We find that the prey's sighting range dominates their life expectancy and the predator profits more from a bad eyesight of the prey than from his own good eye sight. We characterise the dynamics ...

  19. New parasitoid-predator associations: female parasitoids do not avoid competition with generalist predators when sharing invasive prey

    Science.gov (United States)

    Chailleux, Anaïs; Wajnberg, Eric; Zhou, Yuxiang; Amiens-Desneux, Edwige; Desneux, Nicolas

    2014-12-01

    Optimal habitat selection is essential for species survival in ecosystems, and interspecific competition is a key ecological mechanism for many observed species association patterns. Specialized animal species are commonly affected by resource and interference competition with generalist and/or omnivorous competitors, so avoidance behavior could be expected. We hypothesize that specialist species may exploit broad range cues from such potential resource competitors (i.e., cues possibly common to various generalist and/or omnivorous predators) to avoid costly competition regarding food or reproduction, even in new species associations. We tested this hypothesis by studying short-term interactions between a native larval parasitoid and a native generalist omnivorous predator recently sharing the same invasive host/prey, the leaf miner Tuta absoluta. We observed a strong negative effect of kleptoparasitism (food resource stealing) instead of classical intraguild predation on immature parasitoids. There was no evidence that parasitoid females avoided the omnivorous predator when searching for oviposition sites, although we studied both long- and short-range known detection mechanisms. Therefore, we conclude that broad range cue avoidance may not exist in our biological system, probably because it would lead to too much oviposition site avoidance which would not be an efficient and, thus, beneficial strategy. If confirmed in other parasitoids or specialist predators, our findings may have implications for population dynamics, especially in the current context of increasing invasive species and the resulting creation of many new species associations.

  20. Behavioral responses associated with a human-mediated predator shelter.

    Directory of Open Access Journals (Sweden)

    Graeme Shannon

    Full Text Available Human activities in protected areas can affect wildlife populations in a similar manner to predation risk, causing increases in movement and vigilance, shifts in habitat use and changes in group size. Nevertheless, recent evidence indicates that in certain situations ungulate species may actually utilize areas associated with higher levels of human presence as a potential refuge from disturbance-sensitive predators. We now use four-years of behavioral activity budget data collected from pronghorn (Antilocapra americana and elk (Cervus elephus in Grand Teton National Park, USA to test whether predictable patterns of human presence can provide a shelter from predatory risk. Daily behavioral scans were conducted along two parallel sections of road that differed in traffic volume--with the main Teton Park Road experiencing vehicle use that was approximately thirty-fold greater than the River Road. At the busier Teton Park Road, both species of ungulate engaged in higher levels of feeding (27% increase in the proportion of pronghorn feeding and 21% increase for elk, lower levels of alert behavior (18% decrease for pronghorn and 9% decrease for elk and formed smaller groups. These responses are commonly associated with reduced predatory threat. Pronghorn also exhibited a 30% increase in the proportion of individuals moving at the River Road as would be expected under greater exposure to predation risk. Our findings concur with the 'predator shelter hypothesis', suggesting that ungulates in GTNP use human presence as a potential refuge from predation risk, adjusting their behavior accordingly. Human activity has the potential to alter predator-prey interactions and drive trophic-mediated effects that could ultimately impact ecosystem function and biodiversity.

  1. Perceptual advertisement by the prey of stalking or ambushing predators.

    Science.gov (United States)

    Broom, Mark; Ruxton, Graeme D

    2012-12-21

    There has been previous theoretical explorations of the stability of signals by prey that they have detected a stalking or ambush predator, where such perceptual advertisement dissuades the predator from attacking. Here we use a game theoretical model to extend the theory to consider some empirically-motivated complexities: (i) many perceptual advertisement signals appear to have the potential to vary in intensity, (ii) higher intensity signals are likely to be most costly to produce, and (iii) some high-cost signals (such as staring directly at the predator) can only be utilised if the prey is very confident of the existence of a nearby predator (that is, there are reserved or unfakable signals). We demonstrate that these complexities still allow for stable signalling. However, we do not find solutions where prey use a range of signal intensities to signal different degrees of confidence in the proximity of a predator; with prey simply adopting a binary response of not signalling or always signalling at the same fixed level. However this fixed level will not always be the cheapest possible signal, and we predict that prey that require more certainty about proximity of a predator will use higher-cost signals. The availability of reserved signals does not prohibit the stability of signalling based on lower-cost signals, but we also find circumstances where only the reserved signal is used. We discuss the potential to empirically test our model predictions, and to develop theory further to allow perceptual advertisement to be combined with other signalling functions. Copyright © 2012 Elsevier Ltd. All rights reserved.

  2. Strike mechanics of an ambush predator: the spearing mantis shrimp.

    Science.gov (United States)

    deVries, M S; Murphy, E A K; Patek, S N

    2012-12-15

    Ambush predation is characterized by an animal scanning the environment from a concealed position and then rapidly executing a surprise attack. Mantis shrimp (Stomatopoda) consist of both ambush predators ('spearers') and foragers ('smashers'). Spearers hide in sandy burrows and capture evasive prey, whereas smashers search for prey away from their burrows and typically hammer hard-shelled, sedentary prey. Here, we examined the kinematics, morphology and field behavior of spearing mantis shrimp and compared them with previously studied smashers. Using two species with dramatically different adult sizes, we found that strikes produced by the diminutive species, Alachosquilla vicina, were faster (mean peak speed 5.72±0.91 m s(-1); mean duration 3.26±0.41 ms) than the strikes produced by the large species, Lysiosquillina maculata (mean peak speed 2.30±0.85 m s(-1); mean duration 24.98±9.68 ms). Micro-computed tomography and dissections showed that both species have the spring and latch structures that are used in other species for producing a spring-loaded strike; however, kinematic analyses indicated that only A. vicina consistently engages the elastic mechanism. In the field, L. maculata ambushed evasive prey primarily at night while hidden in burrows, striking with both long and short durations compared with laboratory videos. We expected ambush predators to strike with very high speeds, yet instead we found that these spearing mantis shrimp struck more slowly and with longer durations than smashers. Nonetheless, the strikes of spearers occurred at similar speeds and durations to those of other aquatic predators of evasive prey. Although counterintuitive, these findings suggest that ambush predators do not actually need to produce extremely high speeds, and that the very fastest predators are using speed to achieve other mechanical feats, such as producing large impact forces.

  3. Risk of predation makes foragers less choosy about their food.

    Science.gov (United States)

    Charalabidis, Alice; Dechaume-Moncharmont, François-Xavier; Petit, Sandrine; Bohan, David A

    2017-01-01

    Animals foraging in the wild have to balance speed of decision making and accuracy of assessment of a food item's quality. If resource quality is important for maximizing fitness, then the duration of decision making may be in conflict with other crucial and time consuming tasks, such as anti-predator behaviours or competition monitoring. Individuals facing the risk of predation and/or competition should adjust the duration of decision making and, as a consequence, their level of choosiness for resources. When exposed to predation, the forager could either maintain its level of choosiness for food items but accept a reduction in the amount of food items consumed or it could reduce its level of choosiness and accept all prey items encountered. Under competition risk, individuals are expected to reduce their level of choosiness as slow decision making exposes individuals to a higher risk of opportunity costs. To test these predictions, the level of choosiness of a seed-eating carabid beetle, Harpalus affinis, was examined under 4 different experimental conditions of risk: i) predation risk; ii) intraspecific competition; iii) interspecific competition; and, iv) control. All the risks were simulated using chemical cues from individual conspecifics or beetles of different species that are predatory or granivorous. Our results show that when foraging under the risk of predation, H. affinis individuals significantly reduce their level of choosiness for seeds. Reductions in level of choosiness for food items might serve as a sensible strategy to reduce both the total duration of a foraging task and the cognitive load of the food quality assessment. No significant differences were observed when individuals were exposed to competition cues. Competition, (i.e opportunity cost) may not be perceived as risk high enough to induce changes in the level of choosiness. Our results suggest that considering the amount of items consumed, alone, would be a misleading metric when

  4. Predator diversity and identity drive interaction strength and trophic cascades in a food web.

    Science.gov (United States)

    Otto, Sonja B; Berlow, Eric L; Rank, Nathan E; Smiley, John; Brose, Ulrich

    2008-01-01

    Declining predator diversity may drastically affect the biomass and productivity of herbivores and plants. Understanding how changes in predator diversity can propagate through food webs to alter ecosystem function is one of the most challenging ecological research topics today. We studied the effects of predator removal in a simple natural food web in the Sierra Nevada mountains of California (USA). By excluding the predators of the third trophic level of a food web in a full-factorial design, we monitored cascading effects of varying predator diversity and composition on the herbivorous beetle Chrysomela aeneicollis and the willow Salix orestera, which compose the first and second trophic levels of the food web. Decreasing predator diversity increased herbivore biomass and survivorship, and consequently increased the amount of plant biomass consumed via a trophic cascade. Despite this simple linear mean effect of diversity on the strength of the trophic cascade, we found additivity, compensation, and interference in the effects of multiple predators on herbivores and plants. Herbivore survivorship and predator-prey interaction strengths varied with predator diversity, predator identity, and the identity of coexisting predators. Additive effects of predators on herbivores and plants may have been driven by temporal niche separation, whereas compensatory effects and interference occurred among predators with a similar phenology. Together, these results suggest that while the general trends of diversity effects may appear linear and additive, other information about species identity was required to predict the effects of removing individual predators. In a community that is not temporally well-mixed, predator traits such as phenology may help predict impacts of species loss on other species. Information about predator natural history and food web structure may help explain variation in predator diversity effects on trophic cascades and ecosystem function.

  5. Plastic responses of a sessile prey to multiple predators: a field and experimental study.

    Directory of Open Access Journals (Sweden)

    Philipp Emanuel Hirsch

    Full Text Available Theory predicts that prey facing a combination of predators with different feeding modes have two options: to express a response against the feeding mode of the most dangerous predator, or to express an intermediate response. Intermediate phenotypes protect equally well against several feeding modes, rather than providing specific protection against a single predator. Anti-predator traits that protect against a common feeding mode displayed by all predators should be expressed regardless of predator combination, as there is no need for trade-offs.We studied phenotypic anti-predator responses of zebra mussels to predation threat from a handling-time-limited (crayfish and a gape-size-limited (roach predator. Both predators dislodge mussels from the substrate but diverge in their further feeding modes. Mussels increased expression of a non-specific defense trait (attachment strength against all combinations of predators relative to a control. In response to roach alone, mussels showed a tendency to develop a weaker and more elongated shell. In response to crayfish, mussels developed a harder and rounder shell. When exposed to either a combination of predators or no predator, mussels developed an intermediate phenotype. Mussel growth rate was positively correlated with an elongated weaker shell and negatively correlated with a round strong shell, indicating a trade-off between anti-predator responses. Field observations of prey phenotypes revealed the presence of both anti-predator phenotypes and the trade-off with growth, but intra-specific population density and bottom substrate had a greater influence than predator density.Our results show that two different predators can exert both functionally equivalent and inverse selection pressures on a single prey. Our field study suggests that abiotic factors and prey population density should be considered when attempting to explain phenotypic diversity in the wild.

  6. Does Predation Risk Affect Mating Behavior? An Experimental Test in Dumpling Squid (Euprymna tasmanica)

    Science.gov (United States)

    Franklin, Amanda M.; Squires, Zoe E.; Stuart-Fox, Devi

    2014-01-01

    Introduction One of the most important trade-offs for many animals is that between survival and reproduction. This is particularly apparent when mating increases the risk of predation, either by increasing conspicuousness, reducing mobility or inhibiting an individual's ability to detect predators. Individuals may mitigate the risk of predation by altering their reproductive behavior (e.g. increasing anti-predator responses to reduce conspicuousness). The degree to which individuals modulate their reproductive behavior in relation to predation risk is difficult to predict because both the optimal investment in current and future reproduction (due to life-history strategies) and level of predation risk may differ between the sexes and among species. Here, we investigate the effect of increased predation risk on the reproductive behavior of dumpling squid (Euprymna tasmanica). Results Females, but not males, showed a substantial increase in the number of inks (an anti-predator behavior) before mating commenced in the presence of a predator (sand flathead Platycephalus bassensis). However, predation risk did not affect copulation duration, the likelihood of mating, female anti-predator behavior during or after mating or male anti-predator behavior at any time. Conclusions Inking is a common anti-predator defense in cephalopods, thought to act like a smokescreen, decoy or distraction. Female dumpling squid are probably using this form of defense in response to the increase in predation risk prior to mating. Conversely, males were undeterred by the increase in predation risk. A lack of change in these variables may occur if the benefit of completing mating outweighs the risk of predation. Prioritizing current reproduction, even under predation risk, can occur when the chance of future reproduction is low, there is substantial energetic investment into mating, or the potential fitness payoffs of mating are high. PMID:25551378

  7. Food webs and intraguild predation: community interactions of a native mesocarnivore.

    Science.gov (United States)

    Thompson, Craig M; Gese, Eric M

    2007-02-01

    Trophic level interactions between predators create complex relationships such as intraguild predation. Theoretical research has predicted two possible paths to stability in intraguild systems: intermediate predators either outcompete higher-order predators for shared resources or select habitat based on security. The effects of intraguild predation on intermediate mammalian predators such as swift foxes (Vulpes velox) are not well understood. We examined the relationships between swift foxes and both their predators and prey, as well the effect of vegetation structure on swift fox-coyote (Canis latrans) interactions, between August 2001 and August 2004. In a natural experiment created by the Pinon Canyon Maneuver Site in southeastern Colorado, USA, we documented swift fox survival and density in a variety of landscapes and compared these parameters in relation to prey availability, coyote abundance, and vegetation structure. Swift fox density varied significantly between study sites, while survival did not. Coyote abundance was positively related to the basal prey species and vegetation structure, while swift fox density was negatively related to coyote abundance, basal prey species, and vegetation structure. Our results support the prediction that, under intraguild predation in terrestrial systems, top predator distribution matches resource availability (resource match), while intermediate predator distribution inversely matches predation risk (safety match). While predation by coyotes may be the specific cause of swift fox mortality in this system, the more general mechanism appears to be exposure to predation moderated by shrub density.

  8. The Truth About the Internet and Online Predators

    CERN Document Server

    Dingwell, Heath; Peterson, Fred L

    2011-01-01

    To help readers avoid and recognize risky behaviors, The Truth About the Internet and Online Predators explains many of the dangers associated with the Internet. The A-to-Z entries detail the social, legal, and personal risks of Internet use, while personal testimonies and question-and-answer sections provide readers with an inside look at common issues online. Entries include:. Bullies and cyberbullying. Characteristics of online predators. Chat rooms and instant messaging. Internet safety. Parental control. Peers and peer pressure. Phishing and pharming. Privacy issues. Social networking Web

  9. Cannibalism in discrete-time predator-prey systems.

    Science.gov (United States)

    Chow, Yunshyong; Jang, Sophia R-J

    2012-01-01

    In this study, we propose and investigate a two-stage population model with cannibalism. It is shown that cannibalism can destabilize and lower the magnitude of the interior steady state. However, it is proved that cannibalism has no effect on the persistence of the population. Based on this model, we study two systems of predator-prey interactions where the prey population is cannibalistic. A sufficient condition based on the nontrivial boundary steady state for which both populations can coexist is derived. It is found via numerical simulations that introduction of the predator population may either stabilize or destabilize the prey dynamics, depending on cannibalism coefficients and other vital parameters.

  10. Spatio-temporal dynamics of bumblebees foraging under predation risk

    CERN Document Server

    Lenz, Friedrich; Chittka, Lars; Chechkin, Aleksei V; Klages, Rainer

    2011-01-01

    We study bumblebees searching for nectar in a laboratory experiment with and without different types of artificial spiders as predators. We find that the flight velocities obey mixed probability distributions reflecting the access to the food sources while the threat posed by the spiders shows up only in the velocity correlations. This means that the bumblebees adjust their flight patterns spatially to the environment and temporally to the predation risk. Key information on response to environmental changes is thus contained in temporal correlation functions and not in spatial distributions.

  11. Inundative Field Releases and Evaluation of Three Predators for Bemisia tabasi (Hemiptera: Aleyrodidae) Management in Three Vegetable Crops

    Science.gov (United States)

    The sweetpotato whitefly, Bemisia tabaci (Gennadius), is a global pest on numerous crops, including vegetables. Weekly inundative releases of a coccinellid predator (Coccinella undecimpunctata L.), a mirid predator [Macrophillus caliginosus (Wagner)] and a neuropteran predator [Chrysoperla carnea S...

  12. The impact of dry-land sprint start training on the short track speed skating start.

    Science.gov (United States)

    Haug, William B; Drinkwater, Eric J; Cicero, Nicholas J; Barthell, J Anthony; Chapman, Dale W

    2017-05-05

    This investigation sought to determine the effects of dry-land sprint start training on short track speed skating (STSS) start performance. Nine highly trained short track athletes completed a control period of normal STSS training followed by a four-week training intervention. Before and after the control and intervention periods, athletes performed three electronically timed dry-land and on-ice 14.43 m maximal sprint start efforts. The intervention consisted of two sprint sessions per week consisting of nine electronically timed 14.43 m dry-land sprint starts in addition to normal STSS training. The control period resulted in no substantial change in on-ice start performance (Mean Δ: -0.01 s, 95% Confidence Limits (CL): -0.08 to 0.05 s; Effect Size (ES): -0.05; Trivial) however, a small change was observed in dry-land start performance (Mean Δ: -0.07 s, 95% CL: -0.13 to -0.02 s; ES: -0.49). Following brief specific dry-land sprint start training a small improvement was observed in both on-ice (Mean Δ: -0.07 s, 95% CL: -0.13 to -0.01 s; ES: -0.33) and dry-land (Mean Δ: -0.04 s, 95% CL: -0.09 to 0.00 s; ES: -0.29) start performance. This investigation suggests STSS start performance can be improved through a brief dry-land sprint start training program.

  13. Guidelines for starting today's private practice

    Directory of Open Access Journals (Sweden)

    Schmitz ED

    2012-11-01

    Full Text Available No abstract available. Article truncated at 150 words. Starting a new practice may seem like a daunting task. The purpose of this article is to demystify the process of creating a new practice from the beginning. The cardinal rule is to keep costs low and not to outsource work that can easily be performed by any competent physician and staff. You do not need a manager, lawyer, business partner, coder or biller individually; you may be able to perform many of these services yourself. What you do need is a commitment to making your practice a success. Do not spend too much on your office space, furnishings or equipment. Start with the bare essentials. Immediately start applying to all insurance companies especially Medicare. Request an employer identification number. Set up a basic business banking account and submit the account number to the insurance companies you plan to work with. You can purchase an entire electronic healthcare record (EHR …

  14. Two-Man Bobsled Push Start Analysis

    Directory of Open Access Journals (Sweden)

    Lopes Alexandre Dias

    2016-04-01

    Full Text Available The importance of push start times on bobsled performance was evidenced by some studies, but at this moment there is no article to the authors’ knowledge that describes the bobsled push start. Thus, the objectives of this study were to describe the two-man bobsled push start, analyze the differences between teams, and estimate the most important variable analyzed. We hypothesized that the pilot and brakeman athletes’ movement patterns during a bobsled pushing start can be described. The images used in this study were obtained during the men’s two-man XIV World Championship of Bobsled (2004. Fifteen best teams participating in the championship were recorded, and four start runs for each team were analyzed. The videos were captured by two digital video cameras. The pilot athletes were analyzed during the moment that they touched the lateral push bar of the sled, and the brakemen were analyzed during the first take-off and first landing. The teams were pooled in three groups of five teams using the final ranking of pushing time. We concluded that there was a distinct pattern movement for pilots and brakemen. The initial position of the majority of the pilots was localized slightly behind the bar. After touching the lateral bar, the pilots remained in a semi-squat position, pushing the sled forward in a pattern of marching movement. All brakemen used the board attached to the track as a support for both feet at the start. The brakeman gave the greatest contribution to break the inertia of the sled. There was no significant difference of movement between the three groups analyzed for the pilot and the brakeman.

  15. Red fox predation on breeding ducks in midcontinent North America

    Science.gov (United States)

    Sargeant, Alan B.; Allen, Stephen H.; Eberhardt, Robert T.

    1984-01-01

    Red fox (Vulpes vulpes) predation on nesting ducks was assessed by examining 1,857 adult duck remains found at 1,432 fox rearing dens from 1968 to 1973. Dabbling ducks were much more vulnerable to foxes than diving ducks. Dabbling ducks (1,798) found at dens consisted of 27% blue-winged teals (Anas discors), 23% mallards (A. platyrhynchos), 20% northern pintails (A. acuta), 9% northern shovelers (Spatula clypeata), 8% gadwalls (A. strepera), 3% green-winged teals (A. crecca), 2% American wigeons (A. americana), and 10% unidentified. Relative abundance of individual species and nesting chronology were the most important factors affecting composition of ducks taken by foxes. Seventy-six percent of 1,376 adult dabbling ducks and 40% of 30 adult diving ducks for which sex was determined were hens. In western North Dakota and western South Dakota, 65% of mallard and northern pintail remains found at dens were hens compared with 76% in eastern North Dakota and eastern South Dakota (P fox predation rates on ducks. Predation rate indices ranged from 0.01 duck/den in Iowa to 1.80 ducks/den in eastern North Dakota. Average annual predation rate indices for dabbling ducks in a 3-county intensive study area in eastern North Dakota were closely correlated with May pond numbers (r = 0.874, P foxes than hens of late nesting species. Predation rate indices were expanded to estimate total numbers of ducks taken by fox families during the denning season. Estimated numbers of dabbling ducks taken annually by individual fox families in 2 physiographic regions comprising the intensive study area ranged from 16.1 to 65.9. Predation was highest during wet years and lowest during dry years and averaged lower, but was more variable, in the region where tillage was greatest and wetland water levels were least stable. Predation in the intensive study area averaged 2.97 adult dabbling ducks/ km2/year and represented an estimated average annual loss of 13.5% of hen and 4.5% of drake

  16. Company start-up costs and employment

    OpenAIRE

    Christopher Pissarides

    2002-01-01

    I study the role of company start-up costs for employment performance. The model is search equilibrium with a new concept for firms. Agents have an innate managerial ability and make a career choice to become either managers or workers. Managers set up firms, post jobs and match with workers. Managers set up firms, post jobs and match with workers. I show that in equilibrium, career choice and job creation are jointly determined. Higher start-up costs reduce overall employment but increase th...

  17. Getting started with Microsoft Lync server 2013

    CERN Document Server

    Volpe, Fabrizio

    2013-01-01

    This book has a practical approach with a lot of step-by-step guides and explanations as to where and why we're doing the various operations.Getting Started with Microsoft Lync Server 2013 is a starting point for system administrators, IT pros, unified communication technicians, and decision makers in companies or in the consultancy business. For people who have never managed Lync (or a U.C. product), the book will guide you through the basic concepts and mistakes. If you are already managing a Lync deployment you will find important explanations and ideas put together in a single text. If you

  18. Smart or Diverse Start-up Teams?

    DEFF Research Database (Denmark)

    Hoogendoorn, Sander; Parker, Simon C.; Van Praag, Mirjam

    2017-01-01

    This paper explores the relationship between cognitive abilities and team performance in a start-up setting. We argue that performance in this setting hinges on three tasks: opportunity recognition, problem solving, and implementation. We theorize that cognitive ability at the individual level has...... by assigning students to teams based on their measured cognitive abilities. Each team performed a variety of tasks, often involving complex decision making. The key result of the experiment is that the performance of start-up teams first increases and then decreases with ability dispersion. Strikingly, average...

  19. The Lean and Global Start-up

    DEFF Research Database (Denmark)

    Tanev, Stoyan; Rasmussen, Erik Stavnsager

    For several decades researchers have studied start-up companies with a focus on international markets, suppliers and networks from their inception and on companies that are establishing new, agile business models. This has resulted in two streams of research: The Born Global and International New...... Ventures research and research with a focus on the Lean Start-up company. It is our intention in this paper to give a short presentation of the two research streams and show how they can be merged into one with a focus on newly established technology oriented firms that are lean and global from...

  20. Impulsive started flow by a jellyfish

    OpenAIRE

    市川, 誠司; 望月, 修; Seiji, ICHIKAWA; Osamu, MOCHIZUKI; 東洋大; Toyo University

    2008-01-01

    The purpose of this study is to understand the relation between circulation of a vortex ring generated by a disk starting impulsively and necessary force to move the disk. We measured the velocity vector field around the disk by using a PIV method to estimate circulation of the starting vortex ring. It was found that the circulation increased with the square root of the generated energy which is necessary to move the disk. This showed the same relation of the energy of a vortex ring and its c...

  1. Entrepreneur How to Start an Online Business

    CERN Document Server

    Tobin, Lucy

    2012-01-01

    The secrets of the UK’s biggest online entrepreneurs revealed   Thinking of starting a business? Already have a business online and looking to take it to the next level? The wonderful world wide web has made creating a start-up that much easier. Thousands of people are out there reaping the rewards the web can bring. If you want to join them, you’ve come to the right place.  Profiling today’s foremost web entrepreneurs, Lucy Tobin - who meets successful business founders every week writing an enterprise column for The Evening Standard – takes us throug

  2. Potential for exploitative competition, not intraguild predation, between invasive harlequin ladybirds and flowerbugs in urban parks

    DEFF Research Database (Denmark)

    Howe, Andrew Gordon; Ravn, Hans Peter; Pipper, Christian Bressen

    2016-01-01

    In aphidophagous insect communities invaded by the harlequin ladybird Harmonia axyridis Pallas (Coleoptera: Coccinellidae), intraguild predation (IGP) is widely implicated in the displacement of native predators, however, indirect trophic interactions are rarely assessed. Using molecular gut...

  3. To Learn Is To Grow, I: Aldo Leopold, Predator Eradication, and Games Refuges.

    Science.gov (United States)

    Dolph, Gary E.

    1998-01-01

    Follows the evolution in the thinking of Aldo Leopold, a game manager who was initially an advocate of predator eradication but who came to see predators as playing an important role in normally functioning ecosystems. (DDR)

  4. Effects of predation and dispersal on Mastomys natalensis population dynamics in Tanzanian maize fields

    DEFF Research Database (Denmark)

    Vibe-Petersen, Solveig; Leirs, Herwig; de Bruyn, L

    2006-01-01

    1.  We investigate the effects of different levels of predation pressure and rodent dispersal on the population dynamics of the African pest rodent Mastomys natalensis in maize fields in Tanzania. 2.  Three levels of predation risk were used in an experimental set-up: natural level (control......), excluding predators by nets and attracting avian predators by nest boxes and perch poles. Because dispersal of the rodents could mask the predation pressure treatment effects, control and predator exclusion treatments were repeated with enclosed rodent populations. 3.  Population growth during the annual...... risk. Reducing dispersal of rodents removed the effect of predation on population growth and peak size, suggesting that local predators may play a role in driving rodent dispersal, but have otherwise little direct effect on population dynamics....

  5. Factors influencing the predation rates of Anisops breddini (Hemiptera: Notonectidae feeding on mosquito larvae

    Directory of Open Access Journals (Sweden)

    R. Weterings

    2014-12-01

    Full Text Available Notonectidae are a family of water bugs that are known to be important predators of mosquito larvae and have great potential in the biological control of vector mosquitoes. An experiment was conducted to assess mosquito larvae predation by Anisops breddini, a species common to Southeast Asia. The predation rates were recorded in context of prey density, predator density, predator size and prey type. Predation rates were strongly affected by prey type and less by prey density and predator density. They ranged between 1.2 prey items per day for pupae of Aedes aegeypti and Armigeres moultoni to 5.9 for Ae. aegypti larvae. Compared with studies on other Notonectidae species, the predation rates appear low, which is probably caused by the relative small size of the specimens used in this study. An. breddini is very common in the region and often found in urban areas; therefore, the species has potential as a biological control agent.

  6. Natural and human-induced predation on Cape Cormorants at Dyer Island

    NARCIS (Netherlands)

    Voorbergen, A.; Boer, de W.F.; Underhill, L.G.

    2012-01-01

    To develop conservation strategies for vulnerable seabird species that need attention, it is important to know which factors influence their breeding productivity. Predation of eggs and chicks can have large influences on seabird reproduction, especially when human disturbance facilitates predation.

  7. Predator-prey interactions between Synbranchus marmoratus (Teleostei: Synbranchidae) and Hypsiboas pulchellus tadpoles (Amphibia: Hylidae): importance of lateral line in nocturnal predation and effects of fenitrothion exposure.

    Science.gov (United States)

    Junges, Celina M; Lajmanovich, Rafael C; Peltzer, Paola M; Attademo, Andres M; Bassó, Agustín

    2010-11-01

    Environmental contaminants can disrupt interactions between aquatic species by altering community structure. We explored predator-prey interactions between marbled swamp juvenile eels (Synbranchus marmoratus; predator) and anuran tadpoles (Hypsiboas pulchellus; prey) in relation to two aspects: the importance of lateral line in the predator and whether the absence of light modifies predation rates; and the effect of a sub-lethal concentration of fenitrothion on both predator and prey. Eels were tested under two sensory conditions (lateral line intact and lateral line blocked by cobalt chloride) in dark conditions. Predation rates were evaluated using different treatments that combined predator and prey exposed or not to insecticide. Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities were also measured in muscle samples of eels and tadpoles to explore whether fenitrothion affects predator and prey differentially. Marbled swamp eels were more efficient in feeding on tadpoles during the night than during the day, showing that lateral line makes an important contribution to prey detection and capture. Regarding pesticide effects, short-term (6 h) exposure to an ecologically relevant fenitrothion dose of 2.5 mg L(-1) altered the predator-prey relationship by changing prey behaviour, reducing prey detection and therefore increasing tadpole survival. At this concentration, the outcome of the predator-prey relationship appears biased in favor of the exposed tadpoles, which were released from predation risk, despite their altered behaviour and the higher inhibition percentages of tail BChE (70%) and AChE (51%) than in control individuals. Our study involving these model species and agrochemicals demonstrates that fenitrothion affected the outcome of a predator-prey relationship. Further studies are needed, in these species and other native amphibians, to investigate the nature of the mechanisms responsible for the adverse effects of pesticides on

  8. Generalization of predator recognition: Velvet geckos display anti-predator behaviours in response to chemicals from non-dangerous elapid snakes

    Directory of Open Access Journals (Sweden)

    Jonathan K. WEBB, Weiguo DU, David PIKE, Richard SHINE

    2010-06-01

    Full Text Available Many prey species detect chemical cues from predators and modify their behaviours in ways that reduce their risk of predation. Theory predicts that prey should modify their anti-predator responses according to the degree of threat posed by the predator. That is, prey should show the strongest responses to chemicals of highly dangerous prey, but should ignore or respond weakly to chemicals from non-dangerous predators. However, if anti-predator behaviours are not costly, and predators are rarely encountered, prey may exhibit generalised antipredator behaviours to dangerous and non-dangerous predators. In Australia, most elapid snakes eat lizards, and are therefore potentially dangerous to lizard prey. Recently, we found that the nocturnal velvet gecko Oedura lesueurii responds to chemicals from dangerous and non-dangerous elapid snakes, suggesting that it displays generalised anti-predator behaviours to chemicals from elapid snakes. To explore the generality of this result, we videotaped the behaviour of velvet geckos in the presence of chemical cues from two small elapid snakes that rarely consume geckos: the nocturnal golden-crowned snake Cacophis squamulosus and the diurnal marsh snake Hemiaspis signata. We also videotaped geckos in trials involving unscented cards (controls and cologne-scented cards (pungency controls. In trials involving Cacophis and Hemiaspis chemicals, 50% and 63% of geckos spent long time periods (> 3 min freezing whilst pressed flat against the substrate, respectively. Over half the geckos tested exhibited anti-predator behaviours (tail waving, tail vibration, running in response to Cacophis (67% or Hemiaspis (63% chemicals. These behaviours were not observed in control or pungency control trials. Our results support the idea that the velvet gecko displays generalised anti-predator responses to chemical cues from elapid snakes. Generalised responses to predator chemicals may be common in prey species that co-occur with

  9. Spatiotemporal within-plant distribution of the spider mite Tetranychus urticae and associated specialist and generalist predators.

    Science.gov (United States)

    Walzer, A; Moder, K; Schausberger, P

    2009-10-01

    Predators are important determinants of the spatiotemporal distribution of prey within a given habitat. The predator effects may vary with diet specialisation, the associated risk posed to prey and, if multiple predators are present, the predator-predator interactions. We examined the spatiotemporal distribution of the herbivorous spider mite Tetranychus urticae and the associated specialist and generalist predators Phytoseiulus persimilis and Neoseiulus californicus on bean plants. Tetranychus urticae is a key pest on numerous agricultural crops. Both predators are used singly and in combination for biological control of spider mites. Population development and within-plant distribution of the spider mites and the predators were compared among five treatments: T. urticae without predators, with either predator alone and with both predators in combination at full and half densities. The spider mites were suppressed to zero density in both predator combination treatments but not in the single predator treatments. The predators determined the spatiotemporal distribution of the spider mites through density- and behaviour-mediated effects, and these effects were linked to diet specialisation. The specialist P. persimilis exerted stronger density-mediated effects on the spider mite distribution than did the generalist N. californicus. Either predator induced in the spider mites early upward migration on plants. The predators also affected each other's distribution. The aggregation level of N. californicus was lowered by P. persimilis but not vice versa. In combination, the predators were more dispersed than when alone, reducing the predator-free space and leading to the local extinction of T. urticae.

  10. Temporal variation in black-caiman-nest predation in varzea of central Brazilian amazonia.

    Directory of Open Access Journals (Sweden)

    Kelly Torralvo

    Full Text Available On the Amazon floodplain, the main predators of black caiman (Melanosuchus niger eggs are jaguars (Panthera onca, tegu lizards (Tupinambis teguixim, capuchin monkeys (Sapajus macrocephalus and humans (Homo sapiens. In this study, we investigated the relationship between predator attacks on nests and incubation period, and evaluated the influence of initial predation on subsequent predation in the Mamirauá Sustainable Development Reserve. We also evaluated the influence of presence of females near the nests and manipulation of nests on the occurrence of attacks. We compared results from data obtained with camera traps and vestiges left by predators on estimates of rates of predation by different predators. Egg predation was recorded in 32% of the 658 black caiman nests monitored during two years. Our results suggest that the probability of predation on black caiman eggs is relatively constant throughout the incubation period and that predation on eggs was lower when adults, presumably females, were present. Careful opening of nests and handling of eggs did not increase the number of attacks on black caiman nests. Nest opening by a predator appeared to increase the chances of a subsequent attack because most of the attacks on nests occurred soon after a predator first opened the nest. However, attacks by another species of predator do not appear to be necessary to initiate attacks by any other species of predator. Results based on camera traps and vestiges differed, but use of vestiges was adequate for identifying the principal predators on eggs in black caiman nests and, in many circumstances, the vestiges may be better for estimating predation by humans. In this study, opening nests and handling eggs did not increase the number of attacks on black caiman nests.

  11. Fear of predation drives stable and differentiated social relationships in guppies

    OpenAIRE

    Heathcote, Robert J. P.; Darden, Safi K.; Franks, Daniel Wayne; Indar W. Ramnarine; Darren P Croft

    2017-01-01

    Social relationships can have important consequences for fitness in animals. Whilst numerous studies have shown that individuals often join larger groups in response to perceived predation risk (i.e. fear of predation), the importance of predation risk in driving the formation and stability of social relationships within groups has been relatively ignored. We experimentally tested how predation threat influenced fine-scale social network structure using Trinidadian guppies (Poecilia reticulat...

  12. High trees increase sunflower seed predation by birds in an agricultural landscape of Israel

    Directory of Open Access Journals (Sweden)

    Jessica eSchäckermann

    2014-07-01

    Full Text Available Natural habitats in agricultural landscapes promote agro-ecosystem services but little is known about negative effects (dis-services derived by natural habitats such as crop seed predation. Birds are important seed predators and use high landscape structures to perch and hide. High trees in agricultural landscapes may therefore drive seed predation. We examined if the presence, the distance and the percentages of high trees (tree height >5 m and the percentages of natural habitat surrounding sunflower fields, increased seed predation by birds in Israel. At the field scale, we assessed seed predation across a sample grid of an entire field. At the landscape scale, we assessed seed predation at the field margins and interiors of 20 sunflower fields. Seed predation was estimated as the percentage of removed seeds from sunflower heads. Distances of sample points to the closest high tree and percentage of natural habitat and of high trees in a 1km radius surrounding the fields were measured.We found that seed predation increased with decreasing distance to the closest high tree at the field and landscape scale. At the landscape scale, the percentage of high trees and natural habitat did not increase seed predation. Seed predation in the fields increased by 37 %, with a maximum seed predation of 92 %, when a high tree was available within zero to 50 m to the sunflower fields. If the closest high tree was further away, seed predation was less than 5 %. Sunflower seed predation by birds can be reduced, when avoiding sowing sunflowers within a radius of 50 m to high trees. Farmers should plan to grow crops, not sensitive to bird seed predation, closer to trees to eventually benefit from ecosystem services provided by birds, such as predation of pest insects, while avoiding these locations for growing crops sensitive to bird seed predation. Such management recommendations are directing towards sustainable agricultural landscapes.

  13. Impact of predation on the polychaete Hediste diversicolor in estuarine intertidal flats

    Science.gov (United States)

    Rosa, Susana; Granadeiro, José Pedro; Vinagre, Catarina; França, Susana; Cabral, Henrique N.; Palmeirim, Jorge M.

    2008-07-01

    In estuarine sediment flats benthic macroinvertebrates are intensively consumed by a variety of predators, such as aquatic birds and nekton (mostly fish and crustaceans). However, there is still a lack of conclusive studies that evaluate if this predation has a relevant impact on the populations of those invertebrates, which are a key element of the estuarine food chain. In the Tagus estuary we experimentally tested and quantified the impact of predation on the polychaete Hediste diversicolor, one of the most important prey for a variety of predators in many estuaries. Using an exclusion experiment, we compared the seasonal variation in the densities of H. diversicolor from February to November in sediment plots (1) available to both bird and nekton predators, (2) just to nekton, and (3) without predators. We also followed changes in the abundance of potential predators throughout the study. The lowest densities were systematically observed in the plots accessible to all predators, followed by those which excluded just birds, and finally by those that excluded all predators. The exclosures were in place for 9 months, at the end of which the average density of H. diversicolor in the plots protected from all predators was eight times greater than in those without any protection. These results demonstrate that predation had a major impact on the densities of H. diversicolor. The relative importance of bird and nekton predation varied along the study, and this seems to be determined by different peaks of abundance of the two types of predators. However, when present in high densities, birds and nekton seem to have a similar impact on H. diversicolor. Our results suggest that predation is a key factor on the population dynamics of H. diversicolor. In addition, the levels of predation that we observed suggest that this polychaete can be a limited resource, and this could have major ecological consequences for predators for which it is a key prey.

  14. Evolution of juvenile growth rates in female guppies (Poecilia reticulata): predator regime or resource level?

    Science.gov (United States)

    Arendt, Jeffrey D; Reznick, David N

    2005-02-07

    Recent theoretical and empirical work argues that growth rate can evolve and be optimized, rather than always being maximized. Chronically low resource availability is predicted to favour the evolution of slow growth, whereas attaining a size-refuge from mortality risk is predicted to favour the evolution of rapid growth. Guppies (Poecilia reticulata) evolve differences in behaviour, morphology and life-history traits in response to predation, thus demonstrating that predators are potent agents of selection. Predators in low-predation environments prey preferentially on small guppies, but those in high-predation environments appear to be non-selective. Because guppies can outgrow their main predator in low- but not high-predation localities, we predict that predation will select for higher growth rates in the low-predation environments.However, low-predation localities also tend to have lower productivity than high-predation localities, yield-ing the prediction that guppies from these sites should have slower growth rates. Here we compare the growth rates of the second laboratory-born generation of guppies from paired high- and low-predation localities from four different drainages. In two out of four comparisons, guppies from high-predation sites grew significantly faster than their low-predation counterparts. We also compare laboratory born descendants from a field introduction experiment and show that guppies introduced to a low-predation environment evolved slower growth rates after 13 years, although this was evident only at the high food level. The weight of the evidence suggests that resource availability plays a more important role than predation in shaping the evolution of growth rates.

  15. Impact of cannibalism on predator-prey dynamics: size-structured interactions and apparent mutualism.

    Science.gov (United States)

    Rudolf, Volker H W

    2008-06-01

    Direct and indirect interactions between two prey species can strongly alter the dynamics of predator-prey systems. Most predators are cannibalistic, and as a consequence, even systems with only one predator and one prey include two prey types: conspecifics and heterospecifics. The effects of the complex direct and indirect interactions that emerge in such cannibalistic systems are still poorly understood. This study examined how the indirect interaction between conspecific and heterospecific prey affects cannibalism and predation rates and how the direct interactions between both species indirectly alter the effect of the cannibalistic predator. I tested for these effects using larvae of the stream salamanders Eurycea cirrigera (prey) and Pseudotriton ruber (cannibalistic predator) by manipulating the relative densities of the conspecific and heterospecific prey in the presence and absence of the predator in experimental streams. The rates of cannibalism and heterospecific predation were proportional to the respective densities and negatively correlated, indicating a positive indirect interaction between conspecific and heterospecific prey, similar to "apparent mutualism." Direct interactions between prey species did not alter the effect of the predator. Although both types of prey showed a similar 30% reduction in night activity and switch in microhabitat use in response to the presence of the predator, cannibalism rates were three times higher than heterospecific predation rates irrespective of the relative densities of the two types of prey. Cumulative predation risks differed even more due to the 48% lower growth rate of conspecific prey. Detailed laboratory experiments suggest that the 3:1 difference in cannibalism and predation rate was due to the higher efficiency of heterospecific prey in escaping immediate attacks. However, no difference was observed when the predator was a closely related salamander species, Gyrinophilus porphyriticus, indicating that

  16. 76 FR 70009 - Head Start Program

    Science.gov (United States)

    2011-11-09

    ..., health, nutritional, and social needs of the children and families they serve and meet program and... administered by the Office of Head Start (OHS), Administration for Children and Families (ACF), Department of... that indicate the great importance of the early years of a child's growth and development. On December...

  17. 30 CFR 75.1913 - Starting aids.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Starting aids. 75.1913 Section 75.1913 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE SAFETY AND HEALTH MANDATORY... required; (2) Used in the presence of open flames or burning flame safety lamps, or when welding or cutting...

  18. Starting wages respond to employer's risk

    NARCIS (Netherlands)

    Berkhout, P.; Hartog, J.; van Ophem, H

    2009-01-01

    Firms hiring fresh graduates face uncertainty on the future productivity of workers. Theory suggests that starting wages reflect this, with lower pay for greater uncertainty. We use the dispersion of exam grades within a field of education as an indicator of the unobserved heterogeneity that

  19. Addressing Tooth Decay in Head Start Children

    Science.gov (United States)

    Knowlden, Adam P.; Hill, Lawrence F.; Alles-White, Monica L.; Cottrell, Randall R.

    2012-01-01

    Tooth decay is the most prevalent chronic disease of childhood. Oral health education and dental services are crucial to reducing the number of children afflicted with dental cavities. Due to limited access to preventative care, Head Start children are particularly vulnerable to tooth decay. This article outlines practical implications of a…

  20. How to Start Intergenerational Programs in Communities.

    Science.gov (United States)

    2002

    This document is designed for use by community organizers in creating, developing and maintaining an intergenerational program. Starting with a brief overview of the Maryland Intergenerational Coalition, the document describes (in short, bulleted entries) the activities and accomplishments of various intergenerational programs in Maryland, such as…

  1. START to Get Ready for Breastfeeding

    Science.gov (United States)

    Breastfeeding is a great way to give your baby the nutrients he or she needs to grow and develop. Breastfeeding also can help you and your baby form a special bond. Breastfeeding can be good for both of you if you know where to S-T-A-R-T.

  2. Systematic clustering of transcription start site landscapes

    DEFF Research Database (Denmark)

    Zhao, Xiaobei; Valen, Eivind; Parker, Brian J

    2011-01-01

    Genome-wide, high-throughput methods for transcription start site (TSS) detection have shown that most promoters have an array of neighboring TSSs where some are used more than others, forming a distribution of initiation propensities. TSS distributions (TSSDs) vary widely between promoters...

  3. Can Students Predict Starting Salaries? Yes!

    Science.gov (United States)

    Webbink, Dinand; Hartog, Joop

    2004-01-01

    We use Dutch panel data in which students have been asked to state their expected starting salary and confront these with realisations four years later. Both level and structure of expectations and realisations are remarkably close: we barely find systematic under- or overestimation effects.

  4. Verifying the INF and START treaties

    Energy Technology Data Exchange (ETDEWEB)

    Ifft, Edward [School of Foreign Service, Georgetown University, Washington, DC 20057 (United States)

    2014-05-09

    The INF and START Treaties form the basis for constraints on nuclear weapons. Their verification provisions are one of the great success stories of modern arms control and will be an important part of the foundation upon which the verification regime for further constraints on nuclear weapons will be constructed.

  5. From Jam to Start-up

    DEFF Research Database (Denmark)

    Bering Kjæhr, Emil; Lyngbye Hvid Jensen, Jane; Schoenau-Fog, Henrik

    2015-01-01

    the foundation for new start-up companies. There are, however, an even larger group of very creative and innovative games and artifacts with great potential that go unpublished. This potentially leads to a loss of entrepreneurial opportunities and ultimately the jobs and careers such games could have fostered...

  6. Single phase induction motor with starting performance

    Energy Technology Data Exchange (ETDEWEB)

    Popescu, M.; Demeter, E. [Research Institute for Electrical Machines, ICPE-ME, Bucharest (Romania); Navrapescu, V. [University `Politehnica` Bucharest, Electrical Engineering Faculty Splaiul Independentei, Bucharest (Romania)

    1997-12-31

    The paper presents problems related to a special type of single phase induction motor. The main novelty consists in the use of a conducting (aluminium casted) shell distributed on the periferic region of the rotor. As a result the starting performance, as well as the rated ones, is much improved in comparison with the conventional construction. (orig.) 4 refs.

  7. Start-Up Success: Collection Development

    Science.gov (United States)

    Awe, Susan C.

    2010-01-01

    All those who dream of working for themselves and being their own boss, whether they are fresh college graduates, recently unemployed, or newly retired from one career, have a thousand questions about where and how to begin. New entrepreneurs especially will need professional, expert help to start and run a small business effectively and…

  8. Getting started with OrientDB

    CERN Document Server

    Tesoriero, Claudio

    2013-01-01

    A standard tutorial aimed at making you an OrientDB expert, through the use of practical examples, explained in a step-by-step format.Getting Started with OrientDB 1.3.0 is great for database designers, developers, and systems engineers. It is assumed that you are familiar with NoSQL concepts, Java, and networking principles.

  9. Start-up incentives the Netherlands

    NARCIS (Netherlands)

    Bekker, S.; van den Eijnden, J.

    2014-01-01

    Generally, there are three different types of start-up incentive for unemployed and inactive people in the Netherlands. The first is a set of incentives for potential entrepreneurs receiving Unemployment Benefits (UB) (Werloosheidwet - WW). Such incentives have existed since 2006 and were adjusted

  10. Starting Salary Outcomes of Cooperative Education Graduates.

    Science.gov (United States)

    Gardner, Philip D.; And Others

    1992-01-01

    Comparison of 370 engineering co-op graduates with 1,037 nonco-op engineering graduates showed that co-op participants had higher starting salaries; 5 or fewer terms of co-op had better effects. Women, especially electrical, mechanical, or chemical majors, had substantially better salaries with co-op experience. (SK)

  11. Predator and prey perception in copepods due to hydromechanical signals

    DEFF Research Database (Denmark)

    Kiørboe, Thomas; Visser, Andre

    1999-01-01

    large and rapidly swimming/sinking prey particles, and (4) that the model can accommodate the 3 orders of magnitude variation in clearance rates observed in the copepod Oithona similis feeding on motile protists and sinking particles. We finally discuss the implications of hydromechanical predator...... and prey perception to trophic interactions and vertical particle fluxes, and suggest important research questions that may be addressed....

  12. Parasite and predator risk assessment: nuanced use of olfactory cues.

    Science.gov (United States)

    Sharp, John G; Garnick, Sarah; Elgar, Mark A; Coulson, Graeme

    2015-10-22

    Foraging herbivores face twin threats of predation and parasite infection, but the risk of predation has received much more attention. We evaluated, experimentally, the role of olfactory cues in predator and parasite risk assessment on the foraging behaviour of a population of marked, free-ranging, red-necked wallabies (Macropus rufogriseus). The wallabies adjusted their behaviour according to these olfactory cues. They foraged less, were more vigilant and spent less time at feeders placed in the vicinity of faeces from dogs that had consumed wallaby or kangaroo meat compared with that of dogs feeding on sheep, rabbit or possum meat. Wallabies also showed a species-specific faecal aversion by consuming less food from feeders contaminated with wallaby faeces compared with sympatric kangaroo faeces, whose gastrointestinal parasite fauna differs from that of the wallabies. Combining both parasite and predation cues in a single field experiment revealed that these risks had an additive effect, rather than the wallabies compromising their response to one risk at the expense of the other. © 2015 The Author(s).

  13. The effect of cat Felis catus predation on three breeding ...

    African Journals Online (AJOL)

    Breeding success of Pterodroma macroptera, Procellaria aequinoctialis and Pachyptila vittata salvini in three cat-free and three control areas were used to evaluate the effects of cat Felis catus predation on the avifauna of Marion Island. Breeding success of all three species was significantly higher in the combined cat-free ...

  14. How to Protect Children from Internet Predators: A Phenomenological Study

    Science.gov (United States)

    Alexander, Rodney T.

    2012-01-01

    Teenage Internet users are the fastest growing segment in the Internet user population. These teenagers are at risk of sexual assault from Internet predators. This phenomenological study explored teacher and counselors' perceptions of how to prevent this sexual assault. Twenty-five teacher and counselor participants were interviewed. A…

  15. The effect of cat Felis catus predation on three breeding ...

    African Journals Online (AJOL)

    1987-05-08

    May 8, 1987 ... Breeding success of Pterodroma macroptera, Procellaria aequinoctialis and Pachyptila vittata salvini in three cat-free and three control areas were used to evaluate the effects of cat Felis catus predation on the avifauna of Marion Island. Breeding success of all three species was significantly higher in the ...

  16. Conservation implications when the next predators are known. Chapter 2

    Science.gov (United States)

    Frank R., III Thompson; Christine A. Ribic

    2012-01-01

    Conservation and management of passerines has largely focused on habitat manipulation or restoration because the natural communities on which these birds depend have been destroyed and fragmented. However, productivity is another important aspect of avian conservation, and nest predation can be a large source of nesting mortality for passerines. Recent studies using...

  17. Predation on the angulate tortoise Chersina angulata by the kelp ...

    African Journals Online (AJOL)

    1989-07-25

    Jul 25, 1989 ... parasitism. 3. The high density of gulls on the Island during the breeding season in early summer, may lead to in- creased piracy thus making tortoise predation unre- warding. Siegfried (1977) noted that owing to the loss of prey to piracy by other gulls, mussels are seldom dropped from heights above 3-4 m ...

  18. Parasitology: Parasite survives predation on its host

    DEFF Research Database (Denmark)

    Ponton, Fleur; Lebarbenchon, Camille; Lefèvre, Thierry

    2006-01-01

    As prisoners in their living habitat, parasites should be vulnerable to destruction by the predators of their hosts. But we show here that the parasitic gordian worm Paragordius tricuspidatus is able to escape not only from its insect host after ingestion by a fish or frog but also from the diges...

  19. THE DYNAMICS OF REINTRODUCING, SUPPLEMENTING AND CONTROLLING ENDANGERED PREDATOR POPULATIONS

    OpenAIRE

    Rondeau, Daniel

    1998-01-01

    A dynamic model is developed to analyze the reintroduction of endangered predators. Non-convexities and the conditions under which reintroduction is sub-optimal are studied. Following reintroduction, costly population control should be initiated before marginal animals impose net costs, providing an economic interpretation to changes in the sign of the shadow price.

  20. Using Artificial Nests to Study Nest Predation in Birds

    Science.gov (United States)

    Belthoff, James R.

    2005-01-01

    A simple and effective field exercise that demonstrates factors affecting predation on bird nests is described. With instructor guidance, students in high school biology or college-level biology, ecology, animal behavior, wildlife management or ornithology laboratory courses can collaborate to design field experiments related to nest depredation.

  1. Interactions between predation and disturbances shape prey communities.

    Science.gov (United States)

    Karakoç, Canan; Radchuk, Viktoriia; Harms, Hauke; Chatzinotas, Antonis

    2018-02-14

    Ecological disturbances are important drivers of biodiversity patterns. Many biodiversity studies rely on endpoint measurements instead of following the dynamics that lead to those outcomes and testing ecological drivers individually, often considering only a single trophic level. Manipulating multiple factors (biotic and abiotic) in controlled settings and measuring multiple descriptors of multi-trophic communities could enlighten our understanding of the context dependency of ecological disturbances. Using model microbial communities, we experimentally tested the effects of imposed disturbances (i.e. increased dilution simulating density-independent mortality as press or pulse disturbances coupled with resource deprivation) on bacterial abundance, diversity and community structure in the absence or presence of a protist predator. We monitored the communities immediately before and after imposing the disturbance and four days after resuming the pre-disturbance dilution regime to infer resistance and recovery properties. The results highlight that bacterial abundance, diversity and community composition were more affected by predation than by disturbance type, resource loss or the interaction of these factors. Predator abundance was strongly affected by the type of disturbance imposed, causing temporary relief of predation pressure. Importantly, prey community composition differed significantly at different phases, emphasizing that endpoint measurements are insufficient for understanding the recovery of communities.

  2. Abundance and distribution of avian and marine mammal predators ...

    African Journals Online (AJOL)

    The principal predators associated with this activity were common dolphins Delphinus capensis and Cape gannets Morus capensis, and their nearshore distribution was associated with sardine and East Coast round herring E. teres. Few clupeoids were encountered along the KwaZulu-Natal continental shelf, although ...

  3. Aspidoscelis deppii (Black-bellied Racerunner). Predation by Great Egrets

    Science.gov (United States)

    Reynolds, Robert P.; Whatton, James F.; Gebhard, Christina A.

    2014-01-01

    Aspidoscelis deppii) is widely distributed from Veracruz and Michoacan, Mexico to Costa Rica (Köhler et al. 2006. The Amphibians and Reptiles of El Salvador. Krieger Publishing Co., Malabar, Florida. 238 pp.). Neotropical lizards are abundant and common prey to all classes of terrestrial vertebrates, and bird predation of lizards is well known.

  4. Quantifying predation on Baltic cod early life stages

    DEFF Research Database (Denmark)

    Neumann, Viola; Schaber, Matthias; Eero, Margit

    2017-01-01

    Predation on cod (Gadus morhua) eggs by sprat (Sprattus sprattus) and herring (Clupea harengus) is known to be one of the processes influencing reproductive success of the eastern Baltic cod and has been reported to have contributed to lack of recovery of the stock in the 1990s. This study...

  5. Predation and prey selectivity by Argyrosomus h%/epidotus ...

    African Journals Online (AJOL)

    Argyrosomus hololepidotus (kob) is a top predator in the shallow marine environment of the .... damage to gear. Stations deeper than 30 m were excluded, as this is the maximum depth from which stomach contents were collected. Of the four quarterly surveys, catches made in February and May were combined and ...

  6. Effects of frequent fish predation on corals in Hawaii

    Science.gov (United States)

    Jayewardene, D.; Donahue, M. J.; Birkeland, C.

    2009-06-01

    The abundance of lesions from fish bites on corals was quantified at nine shallow reefs in the main Hawaiian Islands. There were on average 117 bite scars m-2 on Pocillopora meandrina tissue from the barred filefish Cantherhines dumerilii, 69 bites m-2 on Porites compressa tissue, and 4 bites m-2 on Porites lobata tissue from the spotted puffer Arothron meleagris. Across sites, the frequency of A. meleagris bites on P. compressa per unit area of living coral cover declined exponentially with increasing coral cover. P. compressa nubbins in two size classes (1-2 cm and 4-5 cm) were transplanted onto six study reefs. Nubbins in the small size class were entirely removed by bites from A. meleagris, while nubbins ≥4 cm were only partially consumed, leaving them able to recover. At sites with abundant P. compressa, predation had little effect on transplanted nubbins; at sites where P. compressa comprised less than 5% of living cover, all nubbins were preyed upon. A. meleagris bite lesions on P. compressa were monitored through time and fully recovered in 42 ± 4 days. A model of the risk of over-predation (a second predation event before the first is healed) decreased exponentially with increasing coral cover and increased linearly with increasing lesion healing time. The increased risk of over-predation at low coral cover could indicate an Allee effect limiting the recovery of coral populations if coral cover is substantially reduced by natural or anthropogenic disturbances.

  7. Short Communications Predation on tent tortoise and leopard ...

    African Journals Online (AJOL)

    Curator of Herpetology. Port Elizabeth Museum. P.O. Box. 13147, Humewood. 6013. Received 26 June 1991; accepted 9 September 1991. Predation by the pale chanting goshawk Melierax canorus on. Psammobates tentorius and Geoche/one pardalis hatchlings oorrelates with the habitat preference of these tortoise spe-.

  8. Effects of predation danger on migration strategies of sandpipers

    NARCIS (Netherlands)

    Lank, D.B.; Butler, R.W.; Ireland, J.; Ydenberg, R.C.

    2003-01-01

    We examine the potential selective importance of predation danger on the evolution of migration strategies of arctic-breeding calidrid sandpipers. Adult calidrids truncate parental care for reasons not obviously related to levels of food abundance on the breeding areas or at migratory stopover

  9. Effects of seed and seedling predation by small mammals on ...

    African Journals Online (AJOL)

    Seed and seedling predation by small mammals, thought to be significant factors controlling the recruitment of Proteaceae in fynbos shrublands, were studied in a fynbos shrubland before and after a fire in March 1987. Seeds of Protea neriifolia R.Br. were planted inside and outside 14 mm mesh exclosures. The abundance ...

  10. Predator associated morphology in Galaxias platei in Patagonian lakes

    DEFF Research Database (Denmark)

    Milano, D.; Cussac, V.E.; Macchi, P.J.

    2002-01-01

    Among 158 Galaxias platei individuals, collected from nine deep Andean lakes and from one shallow lake on the Patagonian steppe. morphological characters associated with caudal fin length ere negatively correlated with predation intensity as measured by the incidence of piscivory. Fish from lakes...

  11. Stationary Patterns in One-Predator Two-Prey Models

    DEFF Research Database (Denmark)

    Pedersen, Michael; Zhigui, Lin

    1999-01-01

    Weakly-coupled elliptic system decribing models of simple three-species food webs such as the one-predator, two-prey modelis discussed. We show thatthere is no non-constant solution if diffusions or inter-specific competitions are strong, or if the intrinsic growths of the prey are slow...

  12. Stationary Patterns in One-Predator Two-Prey Models

    DEFF Research Database (Denmark)

    Pedersen, Michael; Zhigui, Lin

    1999-01-01

    Weakly-coupled elliptic system decribing models of simple three-species food webs such as the one-predator, two-prey model is discussed. We show that there is no non-constant solution if diffusions or inter-specific competitions are strong, or if the intrinsic growths of the prey are slow...

  13. Fruit Removal and Seed Predation in Two African Trees (Lannea ...

    African Journals Online (AJOL)

    Most L. welwitschii fruits were removed during and after maturation but predispersal seed predation by H. rufobrachium left only 19.9% of the total crop to potential seed dispersal. In contrast, H. rufobrachium rarely fed on L. acida seeds. Sun squirrels consumed about twice (L. acida) to 10 times as much (L. welwitschii) fruits ...

  14. Predation and landscape characteristics independently affect reef fish community organization.

    Science.gov (United States)

    Stier, Adrian C; Hanson, Katharine M; Holbrook, Sally J; Schmitt, Russell J; Brooks, Andrew J

    2014-05-01

    Trophic island biogeography theory predicts that the effects of predators on prey diversity are context dependent in heterogeneous landscapes. Specifically, models predict that the positive effect of habitat area on prey diversity should decline in the presence of predators, and that predators should modify the partitioning of alpha and beta diversity across patchy landscapes. However, experimental tests of the predicted context dependency in top-down control remain limited. Using a factorial field experiment we quantify the effects of a focal predatory fish species (grouper) and habitat characteristics (patch size, fragmentation) on the partitioning of diversity and assembly of coral reef fish communities. We found independent effects of groupers and patch characteristics on prey communities. Groupers reduced prey abundance by 50% and gamma diversity by 45%, with a disproportionate removal of rare species relative to common species (64% and 36% reduction, respectively; an oddity effect). Further, there was a 77% reduction in beta diversity. Null model analysis demonstrated that groupers increased the importance of stochastic community assembly relative to patches without groupers. With regard to patch size, larger patches contained more fishes, but a doubling of patch size led to a modest (36%) increase in prey abundance. Patch size had no effect on prey diversity; however, fragmented patches had 50% higher species richness and modified species composition relative to unfragmented patches. Our findings suggest two different pathways (i.e., habitat or predator shifts) by which natural and/or anthropogenic processes can drive variation in fish biodiversity and community assembly.

  15. First observations of attempted nudibranch predation by sea anemones

    NARCIS (Netherlands)

    Meij, van der S.E.T.; Reijnen, B.T.

    2011-01-01

    On two separate occasions during fieldwork in Semporna (eastern Sabah, Malaysia), sea anemones of the family Edwardsiidae were observed attempting to feed on the nudibranch species Nembrotha lineolata and Phyllidia ocellata. These are the first in situ observations of nudibranch predation by sea

  16. Laricobius osakensis, a hemlock wooly adelgid predator from Japan

    Science.gov (United States)

    Ashley Lamb; Michael E. Montgomery; Ligia Cota Viera; Shigehiko Shiyake; Scott. Salom

    2011-01-01

    The approach for the biological control of hemlock woolly adelgid (HWA), Adelges tsugae Annand, has been to release multiple species of host-specific predators in order to reduce HWA populations below damaging thresholds. Beetles in the genus Laricobius prey excusively on adelgids and have life histories matched closely to that of...

  17. Predation life history responses to increased temperature variability.

    Directory of Open Access Journals (Sweden)

    Miguel Barbosa

    Full Text Available The evolution of life history traits is regulated by energy expenditure, which is, in turn, governed by temperature. The forecasted increase in temperature variability is expected to impose greater stress to organisms, in turn influencing the balance of energy expenditure and consequently life history responses. Here we examine how increased temperature variability affects life history responses to predation. Individuals reared under constant temperatures responded to different levels of predation risk as appropriate: namely, by producing greater number of neonates of smaller sizes and reducing the time to first brood. In contrast, we detected no response to predation regime when temperature was more variable. In addition, population growth rate was slowest among individuals reared under variable temperatures. Increased temperature variability also affected the development of inducible defenses. The combined effects of failing to respond to predation risk, slower growth rate and the miss-match development of morphological defenses supports suggestions that increased variability in temperature poses a greater risk for species adaptation than that posed by a mean shift in temperature.

  18. Killing for Girls: Predation Play and Female Empowerment

    Science.gov (United States)

    Bertozzi, Elena

    2012-01-01

    Predation games--games in which the player is actively encouraged and often required to hunt and kill in order to survive--have historically been the purview of male players. Females, though now much more involved in digital games than before, generally play games that stress traditionally feminine values such as socializing with others, shopping,…

  19. Predation on the angulate tortoise Chersina angulata by the kelp ...

    African Journals Online (AJOL)

    The kelp gull (Larus dominicanus) is an important predator on the angulate tortoise (Chersina angulata) on Dassen Island, Western Cape, South Africa. Tortoise shell fragments (n= 142) were collected and measured. Using regression curves based on 184 live tortoises measured on the island, the size class of tortoises ...

  20. Effects of seed and seedling predation by small mammals on ...

    African Journals Online (AJOL)

    1991-03-04

    Mar 4, 1991 ... Leaf litter may inhibit seed germination (Mc-. Pherson & Muller 1969; Manders 1987) or hinder seed ... was consumed) or drought (where the leaves and stem had wilted). Seasonal predation. In order to ..... The remaining pre-fife mortality was due to herbivory, indicating that herbivory by invertebrates was.

  1. Temporal dynamics of top predators interactions in the Barents Sea.

    Directory of Open Access Journals (Sweden)

    Joël M Durant

    Full Text Available The Barents Sea system is often depicted as a simple food web in terms of number of dominant feeding links. The most conspicuous feeding link is between the Northeast Arctic cod Gadus morhua, the world's largest cod stock which is presently at a historical high level, and capelin Mallotus villosus. The system also holds diverse seabird and marine mammal communities. Previous diet studies may suggest that these top predators (cod, bird and sea mammals compete for food particularly with respect to pelagic fish such as capelin and juvenile herring (Clupea harengus, and krill. In this paper we explored the diet of some Barents Sea top predators (cod, Black-legged kittiwake Rissa tridactyla, Common guillemot Uria aalge, and Minke whale Balaenoptera acutorostrata. We developed a GAM modelling approach to analyse the temporal variation diet composition within and between predators, to explore intra- and inter-specific interactions. The GAM models demonstrated that the seabird diet is temperature dependent while the diet of Minke whale and cod is prey dependent; Minke whale and cod diets depend on the abundance of herring and capelin, respectively. There was significant diet overlap between cod and Minke whale, and between kittiwake and guillemot. In general, the diet overlap between predators increased with changes in herring and krill abundances. The diet overlap models developed in this study may help to identify inter-specific interactions and their dynamics that potentially affect the stocks targeted by fisheries.

  2. Yellowhammers get fatter in the presence of a predator.

    Science.gov (United States)

    Lilliendahl

    1998-05-01

    According to predictions from theoretical models, body mass and the daily foraging pattern of small birds in winter should be sensitive to predation risk. With increased risk of predation birds are expected to lower their body mass and shift their foraging to the afternoons. I studied the effect of predator presence on daily mass gain in captive yellowhammers, Emberiza citrinella. The birds were tested in unisex pairs, one bird being dominant over the other. In the first treatment the amount of food was restricted, and the daily pattern of mass gain was recorded. The second treatment was identical to the first, but, in addition, a stuffed sparrowhawk, Accipiter nisus, was displayed to the birds in the morning. Contrary to predictions from some theoretical models and other studies, the birds gained weight on days when the hawk was shown. Furthermore, the increased foraging happened mainly in the first half of the day, which also contradicts predictions from models. These results could be explained as a response to interrupted foraging, decreasing the probability of the birds acquiring the critical evening body mass. Alternatively, the birds increased their body reserves in preparation to leave a dangerous situation. Both dominance classes showed a similar response. The results suggest that the effects of predators on foraging interruptions should be included in models of daily routines of reserve accumulation. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

  3. Predation of Indianmeal moth larvae by Lyctocoris campestris(F.) (Hemiptera: Anthocoridae) in different stored commodities

    Science.gov (United States)

    Predation rates for the anthocorid predator Lyctocoris campestris (F.) against varying densities of late-instar Plodia interpunctello (Hubner) were compared in whole corn, whole wheat, or folled oat stored commodities. More prey were attacked in corn and wheat than in oats, and female predators gene...

  4. Instream cover and shade mediate avian predation on trout in semi-natural streams

    Science.gov (United States)

    Brooke E. Penaluna; Jason B. Dunham; David L. G. Noakes

    2015-01-01

    Piscivory by birds can be significant, particularly on fish in small streams and during seasonal low flow when available cover from predators can be limited. Yet, how varying amounts of cover may change the extent of predation mortality from avian predators on fish is not clear. We evaluated size-selective survival of coastal cutthroat trout (Oncorhynchus...

  5. Evidence of indirect impacts of introduced trout on native amphibians via facilitation of a shared predator

    Science.gov (United States)

    Karen L. Pope; Justin M. Garwood; Hartwell H. Welsh Jr.; Sharon P. Lawler

    2008-01-01

    Hyperpredation occurs when non-native prey facilitate invasive predators, which then suppress native prey. Direct impacts of introduced fish on amphibians are well studied, but the role of fish in supporting shared predators has not been considered. We present evidence for indirect effects of trout on amphibians through snake predation. Analyses of the diet,...

  6. What Cues Do Ungulates Use to Assess Predation Risk in Dense Temperate Forests?

    NARCIS (Netherlands)

    Kuijper, D.P.J.; Verwijmeren, M.|info:eu-repo/dai/nl/380491796; Churski, M.; Zbyryt, A.; Schmidt, K.; Jedrzejewska, B.; Smit, C.

    2014-01-01

    Anti-predator responses by ungulates can be based on habitat features or on the near-imminent threat of predators. In dense forest, cues that ungulates use to assess predation risk likely differ from half-open landscapes, as scent relative to sight is predicted to be more important. We studied, in

  7. What cues do ungulates use to assess predation risk in dense temperate forests?

    NARCIS (Netherlands)

    Kuijper, Dries P.J.; Verwijmeren, Mart; Churski, Marcin; Zbyryt, Adam; Schmidt, Krzysztof; Jędrzejewska, Bogumiła; Smit, Chris

    2014-01-01

    Anti-predator responses by ungulates can be based on habitat features or on the near-imminent threat of predators. In dense forest, cues that ungulates use to assess predation risk likely differ from half-open landscapes, as scent relative to sight is predicted to be more important. We studied, in

  8. Use of artificial nests to investigate predation on freshwater turtle nests

    Science.gov (United States)

    Michael N. Marchand; John A. Litvaitis; Thomas J. Maier; Richard M. DeGraaf

    2002-01-01

    Habitat fragmentation has raised concerns that populations of generalist predators have increased and are affecting a diverse group of prey. Previous research has included the use of artificial nests to investigate the role of predation on birds that nest on or near the ground. Because predation also is a major factor limiting populations of freshwater turtles, we...

  9. Differences in predators of artificial and real songbirds nests: Evidence of bias in artificial nest studies

    Science.gov (United States)

    Frank R. Thompson; Dirk E. Burhans

    2004-01-01

    In the past two decades, many researchers have used artificial nest to measure relative rates of nest predation. Recent comparisons show that real and artificial nests may not be depredated at the same rate, but no one has examined the mechanisms underlying these patterns. We determined differences in predator-specific predation rates of real and artificial nests. we...

  10. Seed predation and climate impacts on reproductive variation in temperate forests of the southeastern USA

    Science.gov (United States)

    David M. Bell; James S. Clark

    2016-01-01

    Climatic effects on tree recruitment will be determined by the interactive effects of fecundity and seed predation. Evaluating how insect and vertebrate seed predators mediate tree reproductive responses to climate depends on long-term studies of seed production, development, and predation. In this study, our objectives were to (1) assess the effects of...

  11. Variation in nest predation among arid-zone birds | Lloyd | Ostrich ...

    African Journals Online (AJOL)

    Differences in predator avoidance behaviour (deserting the nest vs sitting tight) may explain markedly different daily nest predation risk experienced by the Double-banded Courser Rhinoptilus africanus (0.5%) and Namaqua Sandgrouse Pterocles namaqua (9.2%). Nest predation was inversely related to nest density, but ...

  12. How avian nest site selection responds to predation risk: Testing an 'adaptive peak hypothesis'

    Science.gov (United States)

    Quresh S. Latif; Sacha K. Heath; John T. Rotenberry

    2012-01-01

    1. Nest predation limits avian fitness, so birds should favour nest sites that minimize predation risk. Nevertheless, preferred nest microhabitat features are often uncorrelated with apparent variation in predation rates. 2. This lack of congruence between theory-based expectation and empirical data may arise when birds already occupy ‘adaptive peaks’. If birds nest...

  13. Light-induced migration behaviour of Daphnia modified by food and predator kairamones

    NARCIS (Netherlands)

    Van Gool, E.; Ringelberg, J.

    1998-01-01

    Lake-dwelling waterfleas, Daphnia, often face a dilemma;Food availability is highest, near the water surface, but predation by visually hunting predators is also most severe. Swimming downward at dawn reduces predation risk, but food availability and temperature also decrease with depth. We tested

  14. A functional response model of a predator population foraging in a patchy habitat

    DEFF Research Database (Denmark)

    Nachman, Gösta

    2006-01-01

    1. Functional response models (e.g. Holling's disc equation) that do not take the spatial distributions of prey and predators into account are likely to produce biased estimates of predation rates. 2. To investigate the consequences of ignoring prey distribution and predator aggregation, a general...

  15. Common, but Commonly Overlooked: Red-bellied Woodpeckers as Songbird Nest Predators

    Science.gov (United States)

    Kirsten R. Hazler; Dawn E.W. Drumtra; Matthew R. Marshall; Robert J. Cooper; Paul B. Hamel

    2004-01-01

    Woodpeckers in North America are not widely recognized as nest predators. In this paper, we describe several eyewitness accounts of songbird nest predation by Red-bellied Woodpeckers (Melanerpes carolinus), document evidence that songbirds recognize woodpeckers as nest predators, and show that our observations are consistent with previously published...

  16. Effect of downed woody debris on small mammal anti-predator behavior

    Science.gov (United States)

    Travis M. Hinkelman; John L. Orrock; Susan C Loeb

    2011-01-01

    Anti-Predator behavior can affect prey growth, reproduction, survival, and generate emergent effects in food webs. Small mammals often lower the cost of predation by altering their behavior in response to shrubs, but the importance of other microhabitat features, such as downed woody debris, for anti-predator behavior is unknown. We used giving-up densities to quantify...

  17. Pesticide impacts on predator-prey interactions across two levels of organisation

    DEFF Research Database (Denmark)

    Rasmussen, Jes Jessen; Nørum, Ulrik; Rygaard Jerris, Morten

    2013-01-01

    In this study, we aimed to evaluate the effects of a short pulse exposure of the pyrethroid lambdacyhalothrin (LC) on the predator and anti-predator behaviour of the same species; Gammartts pulex. Predator behaviour, at the level of the individual, was studied in indoor microcosms using video tra...

  18. Avoiding the nest : responses of field sparrows to the threat of nest predation

    Science.gov (United States)

    Dirk E. Burhans

    2000-01-01

    Nest predation is a major source of reproductive failure in birds (Ricklefs 1969, Martin 1992). Birds confronted with an enemy near the nest may use behaviors to deter the prospect of nest predation. The benefits of nest defense have been shown for many agressive species (Martin 1992), but smaller birds that cannot deter predators may need to resort to other behaviors...

  19. Predator in First: A prophylactic biological control strategy for management of multiple pests of pepper

    Science.gov (United States)

    The establishment of biocontrol agents is critical for success of biological control strategies. Predator-In-First (PIF) is a prophylactic control strategy that aims to establish predators before the appearance of pests in an agro-ecosystem. Predator-In-First uses the characteristics of generalist p...

  20. Multiple fish predators : Effects of identity, density, and nutrients on lower trophic levels

    NARCIS (Netherlands)

    Reiss, Katrin; Herriot, Micah B.; Eriksson, Britas Klemens

    2014-01-01

    The ongoing loss of predators is changing the composition of food webs, with largely unknown consequences. In particular, the effects of multiple fish predators on food webs are difficult to predict due to the prevalence of omnivory and intra guild predation. At the same time, many ecosystems

  1. On local(ly) ESS of a pair of prey-predator system with predatory switching.

    Science.gov (United States)

    Mukherjee, D; Roy, A B

    1998-08-01

    This paper concentrates on the study of ecological stability for guaranteeing evolutionary stable strategies (ESS) in a two pre-predator system taking into consideration of handling time, with predatory switching. Here predators are polyphagous in nature. The conditions for ESS of the model system are obtained at the equivalence point. We also derive the invasion conditions of a mutant predator.

  2. Increased pollinator habitat enhances cacao fruit set and predator conservation.

    Science.gov (United States)

    Forbes, Samantha J; Northfield, Tobin D

    2017-04-01

    The unique benefits of wild pollinators to the productivity of agricultural crops have become increasingly recognized in recent decades. However, declines in populations of wild pollinator species, largely driven by the conversion of natural habitat to agricultural land and broad-spectrum pesticide use often lead reductions in the provision of pollination services and crop production. With growing evidence that targeted pollinator conservation improves crop yield and/or quality, particularly for pollination specialist crops, efforts are increasing to substitute agriculturally intensive practices with those that alleviate some of the negative impacts of agriculture on pollinators and the pollination services they provide, in part through the provision of suitable pollinator habitat. Further, similarities between the responses of some pollinators and predators to habitat management suggest that efforts to conserve pollinators may also encourage predator densities. We evaluated the effects of one habitat management practice, the addition of cacao fruit husks to a monoculture cacao farm, on the provision of pollination services and the densities of two groups of entomophagous predators. We also evaluated the impacts of cacao fruit husk addition on pollen limitation, by crossing this habitat manipulation with pollen supplementation treatments. The addition of cacao fruit husks increased the number of fruits per tree and along with hand pollination treatments, increased final yields indicating a promotion of the pollination ecosystem service provided by the specialist pollinators, midges. We also found that cacao fruit husk addition increased the densities of two predator groups, spiders and skinks. Further, the conservation of these predators did not inhibit pollination through pollinator capture or deterrence. The findings show that, with moderate habitat management, both pollinator and predator conservation can be compatible goals within a highly specialized plant

  3. Early Start DENVER Model: A Meta - analysis

    Directory of Open Access Journals (Sweden)

    Jane P. Canoy

    2015-11-01

    Full Text Available Each child with Autism Spectrum Disorder has different symptoms, skills and types of impairment or disorder with other children. This is why the word “spectrum” is included in this disorder. Eapen, Crncec, and Walter, 2013 claimed that there was an emerging evidence that early interventions gives the greatest capacity of child’s development during their first years of life as “brain plasticity” are high during this period. With this, the only intervention program model for children as young as 18 months that has been validated in a randomized clinical trial is “Early Start Denver Model” (ESDM. This study aimed to determine the effectiveness of the outcome of “Early Start Denver Model” (ESDM towards young children with Autism Spectrum Disorders. This study made use of meta-analysis method. In this study, the researcher utilized studies related to “Early Start Denver Model (ESDM” which is published in a refereed journal which are all available online. There were five studies included which totals 149 children exposed to ESDM. To examine the “pooled effects” of ESDM in a variety of outcomes, a meta-analytic procedure was performed after the extraction of data of the concrete outcomes. Comprehensive Meta Analysis Version 3.3.070 was used to analyze the data.  The effectiveness of the outcome of “Early Start Denver Model” towards young children with Autism Spectrum Disorders (ASD highly depends on the intensity of intervention and the younger child age. This study would provide the basis in effectively implementing an early intervention to children with autism such as the “Early Start Denver Model” (ESDM that would show great outcome effects to those children that has “Autism Spectrum Disorder”.

  4. Nonconsumptive effects of a predator weaken then rebound over time.

    Science.gov (United States)

    Kimbro, David L; Grabowski, Jonathan H; Hughes, A Randall; Piehler, Michael F; White, J Wilson

    2017-03-01

    Predators can influence prey traits and behavior (nonconsumptive effects [NCEs]), often with cascading effects for basal resources and ecosystem function. But critiques of NCE experiments suggest that their duration and design produce results that describe the potential importance of NCEs rather than their actual importance. In light of these critiques, we re-evaluated a toadfish (predator), crab (prey), and oyster (resource) NCE-mediated trophic cascade. In a 4-month field experiment, we varied toadfish cue (NCE) and crab density (approximating variation in predator consumptive effects, CE). Toadfish initially benefitted oyster survival by causing crabs to reduce consumption. But this NCE weakened over time (possibly due to prey hunger), so that after 2 months, crab density (CE) dictated oyster survivorship, regardless of cue. However, the NCE ultimately re-emerged on reefs with a toadfish cue, increasing oyster survivorship. At no point did the effect of toadfish cue on mud crab foraging behavior alter oyster population growth or sediment organic matter on the reef, which is a measure of benthic-pelagic coupling. Instead, both decreased with increasing crab density. Thus, within a system shown to exhibit strong NCEs in short-term experiments (days) our study supported predictions from theoretical models: (a) within the generation of individual prey, the relative influence of NCEs appears to cycle over longer time periods (months); and (b) predator CEs, not NCEs, drive longer-term resource dynamics and ecosystem function. Thus, our study implies that the impacts of removing top predators via activities such as hunting and overfishing will cascade to basal resources and ecosystem properties primarily through density-mediated interactions. © 2016 by the Ecological Society of America.

  5. Learning rate and temperament in a high predation risk environment

    Science.gov (United States)

    DePasquale, C.; Wagner, Tyler; Archard, G.A.; Ferguson, B.; Braithwaite, V.A.

    2014-01-01

    Living in challenging environments can influence the behavior of animals in a number of ways. For instance, populations of prey fish that experience frequent, nonlethal interactions with predators have a high proportion of individuals that express greater reaction to risk and increased activity and exploration—collectively known as temperament traits. Temperament traits are often correlated, such that individuals that are risk-prone also tend to be active and explore more. Spatial learning, which requires the integration of many sensory cues, has also been shown to vary in fish exposed to different levels of predation threat. Fish from areas of low predation risk learn to solve spatial tasks faster than fish from high predation areas. However, it is not yet known whether simpler forms of learning, such as learning associations between two events, are similarly influenced. Simple forms of associative learning are likely to be affected by temperament because a willingness to approach and explore novel situations could provide animals with a learning advantage. However, it is possible that routine-forming and inflexible traits associated with risk-prone and increased exploratory behavior may act in the opposite way and make risk-prone individuals poorer at learning associations. To investigate this, we measured temperament in Panamanian bishop fish (Brachyrhaphis episcopi) sampled from a site known to contain many predators. The B. episcopi were then tested with an associative learning task. Within this population, fish that explored more were faster at learning a cue that predicted access to food, indicating a link between temperament and basic learning abilities.

  6. Learning rate and temperament in a high predation risk environment.

    Science.gov (United States)

    DePasquale, C; Wagner, T; Archard, G A; Ferguson, B; Braithwaite, V A

    2014-11-01

    Living in challenging environments can influence the behavior of animals in a number of ways. For instance, populations of prey fish that experience frequent, nonlethal interactions with predators have a high proportion of individuals that express greater reaction to risk and increased activity and exploration-collectively known as temperament traits. Temperament traits are often correlated, such that individuals that are risk-prone also tend to be active and explore more. Spatial learning, which requires the integration of many sensory cues, has also been shown to vary in fish exposed to different levels of predation threat. Fish from areas of low predation risk learn to solve spatial tasks faster than fish from high predation areas. However, it is not yet known whether simpler forms of learning, such as learning associations between two events, are similarly influenced. Simple forms of associative learning are likely to be affected by temperament because a willingness to approach and explore novel situations could provide animals with a learning advantage. However, it is possible that routine-forming and inflexible traits associated with risk-prone and increased exploratory behavior may act in the opposite way and make risk-prone individuals poorer at learning associations. To investigate this, we measured temperament in Panamanian bishop fish (Brachyrhaphis episcopi) sampled from a site known to contain many predators. The B. episcopi were then tested with an associative learning task. Within this population, fish that explored more were faster at learning a cue that predicted access to food, indicating a link between temperament and basic learning abilities.

  7. Study on screening of anti-predator rhizosphere bacterium against Caenorhabditis elegans and its anti predation mechanism

    Directory of Open Access Journals (Sweden)

    HE Qingling

    2016-08-01

    Full Text Available Althoughmicrobial fertilizer is multi-effect,environmental friendly and long-term efficient,its practical application effect is but decreased for being prey by the other creators living in soil frequently.Many bacterium have developed their mechanisms that expel or kill worms to defend themselves from predators.Screening of anti-predator rhizosphere bacterium helps us to find out competitive plant growth promoting rhizobacteria(PGPR.Using Caenorhabditis elegans as sample,this study roughly observed two strains of biocontrol:Pseudomonas aurantiaca JD37 and Pseudomonas fluorescens P13.Using Escherichia coli OP50 as control group,we find the preference order of worms,from highest to lowest,is P13,OP50 and JD37.In slow killing assay,the death rate of worms for JD37 and P13 are 26.12% and 18.66% respectively.The activity and reproduction rate of C.elegans decrease when it is fed on JD37.The results of chemical and micro-biological study show that JD37 cannot produce any currently studied second metabolites which kill worms,while P13 can produce Hydrogen cyanide (HCN.All these results show that JD37 has the ability of anti-predator,and is more competitive under predation pressure,which suggests its broad application prospect as microbial fertilizer.

  8. Does fear beget fear? Risk-mediated habitat selection triggers predator avoidance at lower trophic levels.

    Science.gov (United States)

    Blubaugh, Carmen K; Widick, Ivy V; Kaplan, Ian

    2017-07-20

    Non-consumptive effects (NCEs) of predators are ubiquitous in food webs with well-detailed impacts on trophic cascades over multiple levels. However, integrating NCEs with other predator-mediated interactions, like intraguild predation, as well as context-specific habitat factors that shape top-down pressure, remains a challenge. Focusing on two common seed predators, mice (Peromyscus spp.) and carabid beetles (Coleoptera: Carabidae), we quantify trophic and behavioral consequences of predation risk and availability of refuge vegetation on both intraguild predators (mice) and intraguild prey (beetles). In a 2-year field experiment, we manipulated refuge habitat (red clover), small mammal access, and moonlight, which small mammals use as an indirect cue of predation risk. We found that avoidance of predation risk by mice in simulated moonlight reduced carabid activity density in vegetation by up to 50% compared to exposed habitat, but had no cascading effects on seed predation. We linked patterns observed in the field with behavioral mechanisms by observing beetle foraging activity, and found that exposure to both indirect and direct vertebrate predator cues reduced movement by 50%, consistent with predator-mediated activity reductions observed in the field. However, predation risk increased carabid seed consumption by 43%. Thus, weak effects of predation risk on seed removal in the field may be explained by overcompensatory seed feeding by beetles. This work demonstrates that predators elicit responses that cascade over multiple trophic levels, triggering behavioral changes in species lower on the food chain. These behavior-mediated cascades are controlled by their spatiotemporal context and have important downstream impacts on predator-prey dynamics.

  9. Starting apparatus for internal combustion engines

    Science.gov (United States)

    Dyches, Gregory M.; Dudar, Aed M.

    1997-01-01

    An internal combustion engine starting apparatus uses a signal from a curt sensor to determine when the engine is energized and the starter motor should be de-energized. One embodiment comprises a transmitter, receiver, computer processing unit, current sensor and relays to energize a starter motor and subsequently de-energize the same when the engine is running. Another embodiment comprises a switch, current transducer, low-pass filter, gain/comparator, relay and a plurality of switches to energize and de-energize a starter motor. Both embodiments contain an indicator lamp or speaker which alerts an operator as to whether a successful engine start has been achieved. Both embodiments also contain circuitry to protect the starter and to de-energize the engine.

  10. Sustainability of hatchery-dependent salmonine fisheries in Lake Ontario: The conflict between predator demand and predator supply

    Science.gov (United States)

    Jones, Michael L.; Koonce, Joseph F.; O'Gorman, Robert

    1993-01-01

    The offshore fish community of Lake Ontario is presently dominated by intensively managed, nonnative species: Alewife Alosa pseudoharengus and rainbow smelt Osmerus mordax at the planktivore level and stocked salmonines at the piscivore level. Salmonine stocking rates per unit area of Lake Ontario are the highest in the Great Lakes, and fishery managers are concerned about the sustainability of the fishery under present stocking policies, particularly with the recent collapse of the Lake Michigan fishery for chinook salmon Oncorhynchus tshawytscha. In this paper, we describe and present the results of a simulation model that integrates predator demand estimates derived from bioenergetics, prey and predator population dynamics, and a predation model based on the multiple-species functional response, Model reconstructions of historical alewife biomass trends and salmonine diets corresponded reasonably well with existing data for the period 1978–1992. The simulations suggest that current predator demand does not exceed the threshold beyond which alewife biomass cannot be sustained, but they indicate that the sustainability of the prey fish community is extremely sensitive to fluctuations in overwinter survival of alewife; an additional mortality of 25% in a single winter would be sufficient to cause the collapse of the alewife population. The model includes a number of assumptions and simplifications with a limited empirical basis; better estimates of salmonine survival rates, an evaluation of the importance of spatial and temporal interactions among predators and prey, and incorporation of the effects of recently observed declines in system productivity at lower trophic levels would significantly increase confidence in the model's projections.

  11. Complexity and Chaos in Surgical Start Times

    Directory of Open Access Journals (Sweden)

    Dennis J. Baumgardner

    2016-08-01

    Full Text Available In discussing an article investigating the causes for delay of first-case operating room start times included in this issue of the Journal of Patient-Centered Research and Reviews, the editor uses elements of complexity science and chaos theory to explain that such stubborn problems rarely stem from one of a few isolated causes. Taking a whole systems approach that utilizes flexibility, cross training, enhanced communication, common sense and perhaps mathematical models is suggested to effect positive change.

  12. Starting and developing a surveying business

    CERN Document Server

    Imber, Austen

    2013-01-01

    Starting and Developing a Surveying Business shows how surveyors can develop their own successful small business. For surveyors thinking of taking this step, guidance is provided on the pros and cons which will help the right decision to be made, and the key factors which help see the business through its early stages. For surveyors already running their own small business, consideration is given to factors which will help profitability and growth potential.

  13. New START: The Contentious Road to Ratification

    Directory of Open Access Journals (Sweden)

    Elizabeth Zolotukhina

    2011-01-01

    Full Text Available Senate ratification of the New START treaty re-established effective bilateral inspection and monitoring of American and Russian nuclear holdings and has the potential to further enhance U.S.-Russian cooperation on key issues, including containing the Iranian nuclear program, and further reductions in the two countries' arsenals. Although the accord was widely heralded as a foreign policy success of the Obama administration, the contentious Senate ratification may impede future progress on arms control.

  14. The 2002 Starting Artificial Intelligence Researchers Symposium

    OpenAIRE

    Vidal, Thierry

    2003-01-01

    During the 2002 European Conference on Artificial Intelligence (ECAI-02) was introduced the Starting Artificial Intelligence Researchers Symposium STAIRS), the first-ever international symposium specifically aimed at Ph.D. students in AI. The outcome was a thorough, high-quality, and successful event, with all the features one usually finds in the best international conferences: large international committees, comprehensive coverage, published proceedings, renowned speakers and panelists, sub...

  15. Getting started with nopCommerce

    CERN Document Server

    Atkinson, Brandon

    2013-01-01

    A friendly, tutorial style book, which will help you learn your way through creating a live storefront with nopCommerce in a step-by-step manner.Getting Started with nopCommerce is for anyone who wants to sell products online using nopCommerce. If you are a non-technical person and are discouraged by the complexity of this powerful e-commerce application, then this book is for you.

  16. New Start of “Psychological Thought”

    Directory of Open Access Journals (Sweden)

    Stanislava Stoyanova

    2012-05-01

    Full Text Available The history and the mission of Psychological Thought are presented. The scientific journal “Psychological Thought” started its existence as an idea of the colleagues at the Department of Psychology at South-West University “Neofit Rilski” in 2006. Seven print issues were published from 2006 to 2009 (2 issues per year. Each issue included average ten articles published in Bulgarian or in English.

  17. "Go" signal intensity influences the sprint start.

    Science.gov (United States)

    Brown, Alexander M; Kenwell, Zoltan R; Maraj, Brian K V; Collins, David F

    2008-06-01

    Loud sounds can decrease reaction time (RT) and increase force generated during voluntary contractions. Accordingly, we hypothesized that the loud starter's pistol at the Olympic Games allows runners closer to the starter to react sooner and stronger than runners farther away. RT for the 100/110 m athletics events at the 2004 Olympics were obtained from International Association of Athletics Federations archives and binned by lane. Additionally, 12 untrained participants and four trained sprinters performed sprint starts from starting blocks modified to measure horizontal force. The "go" signal, a recorded gunshot, was randomly presented at 80-100-120 dB. Runners closest to the starter at the Olympics had significantly lower RT than those further away. Mean RT for lane 1 (160 ms) was significantly lower than for lanes 2-8 (175 +/- 5 ms), and RT for lane 2 was significantly lower than that for lane 7. Experimentally, increasing "go" signal intensity from 80-100-120 dB significantly decreased RT from 138 +/- 30 to 128 +/- 25 to 120 +/- 20 ms, respectively. Peak force was not influenced by sound intensity. However, time to peak force was significantly lower for the 120 dB compared to the 80-dB "go" signal for untrained but not trained participants. When a startle response was evoked, RT was 18 ms lower than for starts with no startle. Startle did not alter peak force or time to peak force. Graded decreases in RT may reflect a summation-mediated reduction in audiomotor transmission time, whereas step-like decreases associated with startle may reflect a bypassing of specific cortical circuits. We suggest that procedures presently used to start the Olympic sprint events afford runners closer to the starter the advantage of hearing the "go" signal louder; consequently, they react sooner but not more strongly than their competitors.

  18. Getting started with MariaDB

    CERN Document Server

    Bartholomew, Daniel

    2013-01-01

    A practical, hands-on, beginner-friendly guide to installing and using MariaDB.Getting Started with MariaDB is for anyone who wants to learn more about databases in general or MariaDB in particular. No prior database experience is required. It is assumed that you have basic knowledge of software installation, editing files with a text editor, and using the command line and terminal.

  19. Grass fields as reservoirs for polyphagous predators (Arthropoda) of aphids (Homopt., Aphididae)

    DEFF Research Database (Denmark)

    Gravesen, Eigil Vestergaard; Toft, Søren

    1987-01-01

    , and an unaccessible, fenced area. Numbers of polyphagous predators and aphids were recorded throughout the growing season. In the unfenced areas with high numbers of predators, aphid populations reached only one third the size in the fenced, predator-low areas. June-numbers of several predator groups and species were...... negatively correlated to three measures of aphid population development. Also, carabids as a group and two carabid species showed an aggregative response to aphid densities. For comparison, predators were positively correlated with Collembola numbers in spring, and also showed an aggregative response...

  20. Odour cues influence predation risk at artificial bat roosts in urban bushland.

    Science.gov (United States)

    Threlfall, Caragh; Law, Bradley; Banks, Peter B

    2013-06-23

    Odours that accumulate from roosting can attract predators and increase predation risk. Consequently, selection should favour strategies that allow prey to evade detection by predators, including changing roosts. Insectivorous bats that roost in tree hollows regularly switch roosts and roost in different sized groups, strategies that would alter the accumulation of roost odours and are hypothesized to reduce predation risk. We experimentally manipulated the amount and refresh rate of roosting odour cues at 90 artificial bat roosts in Sydney, Australia, to test the hypothesis that odours increase predator visitation. Predators visited roosts with bat faeces significantly more often than untreated control roosts. Roosts with small amounts of faeces mimicking sites used by solitary bats had the greatest rate of visitation. This suggests that bats roosting alone, rather than in groups, have a greater likelihood of disturbance or predation. Roost switching probably decreases the predictability of finding occupied roosts; however, we show that all roosts (those currently or recently occupied) were visited by predators, suggesting generalist urban predators readily investigate potential roosts. This is the first demonstration that bat odours are attractive to predators that use olfactory cues, showing that bats are at risk of predation in visually cryptic roosts.

  1. Fear of predation alters clone-specific performance in phloem-feeding prey.

    Science.gov (United States)

    Khudr, Mouhammad Shadi; Buzhdygan, Oksana Y; Petermann, Jana S; Wurst, Susanne

    2017-08-09

    Fear of predation has been shown to affect prey fitness and behaviour, however, to date little is known about the underlying genetics of responses to predator-associated risk. In an effort to fill this gap we exposed four naïve clones of green peach aphid (Myzus persicae), maintained on the model crop Brassica oleracea, to different types of cues from aphid lion (Chrysoperla carnea). The respective predation risks, we termed Fear Factors, were either lethal (consumption by predator), or non-lethal (non-consumptive predator-associated cues: plant-tethered predator cadavers and homogenised shoot-sprayed or soil-infused blends of predator remains). Our results show that the non-lethal risk cues differentially impeded prey reproductive success that varied by clone, suggesting genotype-specific response to fear of predation. Furthermore, whether plants were perceived as being safe or risky influenced prey responses as avoidance behaviour in prey depended on clone type. Our findings highlight that intra-specific genetic variation underlies prey responses to consumptive and non-consumptive effects of predation. This allows selection to act on anti-predator responses to fear of predation that may ramify and influence higher trophic levels in model agroecosystems.

  2. Escape and surveillance asymmetries in locusts exposed to a Guinea fowl-mimicking robot predator.

    Science.gov (United States)

    Romano, Donato; Benelli, Giovanni; Stefanini, Cesare

    2017-10-09

    Escape and surveillance responses to predators are lateralized in several vertebrate species. However, little is known on the laterality of escapes and predator surveillance in arthropods. In this study, we investigated the lateralization of escape and surveillance responses in young instars and adults of Locusta migratoria during biomimetic interactions with a robot-predator inspired to the Guinea fowl, Numida meleagris. Results showed individual-level lateralization in the jumping escape of locusts exposed to the robot-predator attack. The laterality of this response was higher in L. migratoria adults over young instars. Furthermore, population-level lateralization of predator surveillance was found testing both L. migratoria adults and young instars; locusts used the right compound eye to oversee the robot-predator. Right-biased individuals were more stationary over left-biased ones during surveillance of the robot-predator. Individual-level lateralization could avoid predictability during the jumping escape. Population-level lateralization may improve coordination in the swarm during specific group tasks such as predator surveillance. To the best of our knowledge, this is the first report of lateralized predator-prey interactions in insects. Our findings outline the possibility of using biomimetic robots to study predator-prey interaction, avoiding the use of real predators, thus achieving standardized experimental conditions to investigate complex and flexible behaviours.

  3. Behavioural responses of feral and domestic guppies (Poecilia reticulata) to predators and their cues.

    Science.gov (United States)

    Swaney, William T; Cabrera-Álvarez, María J; Reader, Simon M

    2015-09-01

    Predation is an important factor during adaptation to novel environments, and the feralisation of introduced domestic species often involves responding appropriately to allopatric predators despite a background of domestication and inbreeding. Twenty years ago, domestic guppies were introduced to a semi-natural environment at Burgers' Zoo in the Netherlands, where they have since been exposed to avian predation. We compared predation-linked behaviours in this feral population and in domestic guppies akin to the original founders. We found that both populations responded to a novel predator and to conspecific alarm cues. However, shoaling, an important anti-predator behaviour, was higher among feral guppies both at baseline and when exposed to the novel predator. We did not observe a linked suite of anti-predator behaviours across shoaling, predator inspection, alarm substance sensitivity and boldness, suggesting that these responses may be decoupled from one another depending on local predation regimes. As we compared two populations, we cannot identify the causal factors determining population differences, however, our results do suggest that shoaling is either a particularly consequential anti-predator adaptation or the most labile of the behaviours we tested. Finally, the behavioural adaptability of domestic guppies may help to explain their success as an invasive species. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. The effects of different predator species on antipredator behavior in the Trinidadian guppy, Poecilia reticulata

    Science.gov (United States)

    Botham, M. S.; Kerfoot, C. J.; Louca, V.; Krause, J.

    2006-09-01

    Different types of predators often elicit different antipredator responses in a common type of prey. Alternatively, some prey species may adopt a general response, which provides limited protection from many different types of predator. The Trinidadian guppy, Poecilia reticulata, is faced with a wide range of different predators throughout its range and is known to display varying levels of antipredator behavior depending on the predator assemblage. Pike cichlids, Crenicichla frenata, are regarded as the primary aquatic guppy predator in streams in the northern mountain range in Trinidad. As such, they are seen to be responsible for many of the differences in morphology, life history traits, and behavior between guppy populations from areas with few predators and those from areas with many pike cichlids. In this study we investigated how guppies responded when faced with different predator species using three common aquatic predators. We exposed shoals of ten guppies to one out of four treatments: no predator (control), pike cichlid, acara cichlid ( Aequidens pulcher), and wolf fish ( Hoplias malabaricus); and we made behavioral observations on both focal individuals and the shoal as a whole. Guppies showed significantly greater levels of predator inspection and shoaling behavior, foraged less, spent more time in the surface water, and stayed in significantly larger shoals when faced with pike cichlids than in other treatments. We discuss these results in the context of multiple predator effects.

  5. Predation cues rather than resource availability promote cryptic behaviour in a habitat-forming sea urchin.

    Science.gov (United States)

    Spyksma, Arie J P; Taylor, Richard B; Shears, Nick T

    2017-03-01

    It is well known that predators often influence the foraging behaviour of prey through the so-called "fear effect". However, it is also possible that predators could change prey behaviour indirectly by altering the prey's food supply through a trophic cascade. The predator-sea urchin-kelp trophic cascade is widely assumed to be driven by the removal of sea urchins by predators, but changes in sea urchin behaviour in response to predators or increased food availability could also play an important role. We tested whether increased crevice occupancy by herbivorous sea urchins in the presence of abundant predatory fishes and lobsters is a response to the increased risk of predation, or an indirect response to higher kelp abundances. Inside two New Zealand marine reserves with abundant predators and kelp, individuals of the sea urchin Evechinus chloroticus were rarer and remained cryptic (i.e. found in crevices) to larger sizes than on adjacent fished coasts where predators and kelp are rare. In a mesocosm experiment, cryptic behaviour was induced by simulated predation (the addition of crushed conspecifics), but the addition of food in the form of drift kelp did not induce cryptic behaviour. These findings demonstrate that the 'fear' of predators is more important than food availability in promoting sea urchin cryptic behaviour and suggest that both density- and behaviourally mediated interactions are important in the predator-sea urchin-kelp trophic cascade.

  6. Lake Pend Oreille Predation Research, Annual Report 2002-2003.

    Energy Technology Data Exchange (ETDEWEB)

    Bassista, Thomas

    2004-02-01

    During August 2002 we conducted a hydroacoustic survey to enumerate pelagic fish >406 mm in Lake Pend Oreille, Idaho. The purpose of this survey was to determine a collective lakewide biomass estimate of pelagic bull trout Salvelinus confluentus, rainbow trout Oncorhynchus mykiss, and lake trout S. namaycush and compare it to pelagic prey (kokanee salmon O. nerka) biomass. By developing hydroacoustic techniques to determine the pelagic predator to prey ratio, we can annually monitor their balance. Hydroacoustic surveys were also performed during December 2002 and February 2003 to investigate the effectiveness of autumn and winter surveys for pelagic predators. The inherent problem associated with hydroacoustic sampling is the inability to directly identify fish species. Therefore, we utilized sonic tracking techniques to describe rainbow trout and lake trout habitat use during our winter hydroacoustic survey to help identify fish targets from the hydroacoustic echograms. During August 2002 we estimated there were 39,044 pelagic fish >406 mm in Lake Pend Oreille (1.84 f/ha). Based on temperature and depth utilization, two distinct groups of pelagic fish >406 mm were located during August; one group was located between 10 and 35 m and the other between 40 and 70 m. The biomass for pelagic fish >406 mm during August 2002 was 73 t (metric ton). This would account for a ratio of 1 kg of pelagic predator for every 2.63 kg of kokanee prey, assuming all pelagic fish >406 mm are predators. During our late fall and winter hydroacoustic surveys, pelagic fish >406 mm were observed at lake depths between 20 and 90 m. During late fall and winter, we tracked three rainbow trout (168 habitat observations) and found that they mostly occupied pelagic areas and predominantly stayed within the top 10 m of the water column. During late fall (one lake trout) and winter (four lake trout), we found that lake trout (184 habitat observations) utilized benthic-nearshore areas 65% of the time

  7. Do mammalian nest predators follow human scent trails in the shortgrass prairie?

    Science.gov (United States)

    Skagen, S.K.; Stanley, T.R.; Dillon, M.B.

    1999-01-01

    Nest predation, the major cause of nest failure in passerines, has exerted a strong influence on the evolution of life history traits of birds. Because human disturbance during nest monitoring may alter predation rates, we investigated whether human scent affected the survival of artificial ground nests in shortgrass prairie. Our experiment consisted of two treatments, one in which there was no attempt to mask human scent along travel routes between artificial nests, and one in which we masked human scent with cow manure, a scent familiar to mammalian predators in the study area. We found no evidence that human scent influenced predation rates, nor that mammalian predators followed human trails between nests. We conclude that scent trails made by investigators do not result in lower nesting success of passerines of the shortgrass prairie where vegetation trampling is minimal, mammalian predators predominate, and avian predators are rare.

  8. One-prey two-predator model with prey harvesting in a food chain interaction

    Science.gov (United States)

    Sayekti, I. M.; Malik, M.; Aldila, D.

    2017-07-01

    The interaction between prey, secondary predator, and primary predator as a mathematical model of the one-prey and two-predator system with constant harvesting in prey population will be introduced in this article. Their interaction might describe as a food pyramid, with the preys is in the lowest level of the pyramid, secondary predators in the middle, and primary predators in the top of the pyramid. Human intervention to controlling prey population is needed and will be analyzed how this will effect on the existence of secondary predator and primary predator population. Equilibrium points and their existence criteria will be analyzed to find a threshold that will guarantee the coexistence of this system. Some numerical simulation will be given to illustrate the analytical results. We find that as long as harvesting rate in prey population is smaller than prey intrinsic growth rate, coexistence might achieve.

  9. Evolutionary Diversification of Prey and Predator Species Facilitated by Asymmetric Interactions.

    Directory of Open Access Journals (Sweden)

    Jian Zu

    Full Text Available We investigate the influence of asymmetric interactions on coevolutionary dynamics of a predator-prey system by using the theory of adaptive dynamics. We assume that the defense ability of prey and the attack ability of predators all can adaptively evolve, either caused by phenotypic plasticity or by behavioral choice, but there are certain costs in terms of their growth rate or death rate. The coevolutionary model is constructed from a deterministic approximation of random mutation-selection process. To sum up, if prey's trade-off curve is globally weakly concave, then five outcomes of coevolution are demonstrated, which depend on the intensity and shape of asymmetric predator-prey interactions and predator's trade-off shape. Firstly, we find that if there is a weakly decelerating cost and a weakly accelerating benefit for predator species, then evolutionary branching in the predator species may occur, but after branching further coevolution may lead to extinction of the predator species with a larger trait value. However, if there is a weakly accelerating cost and a weakly accelerating benefit for predator species, then evolutionary branching in the predator species is also possible and after branching the dimorphic predator can evolutionarily stably coexist with a monomorphic prey species. Secondly, if the asymmetric interactions become a little strong, then prey and predators will evolve to an evolutionarily stable equilibrium, at which they can stably coexist on a long-term timescale of evolution. Thirdly, if there is a weakly accelerating cost and a relatively strongly accelerating benefit for prey species, then evolutionary branching in the prey species is possible and the finally coevolutionary outcome contains a dimorphic prey and a monomorphic predator species. Fourthly, if the asymmetric interactions become more stronger, then predator-prey coevolution may lead to cycles in both traits and equilibrium population densities. The Red

  10. Landscape-moderated bird nest predation in hedges and forest edges

    Science.gov (United States)

    Ludwig, Martin; Schlinkert, Hella; Holzschuh, Andrea; Fischer, Christina; Scherber, Christoph; Trnka, Alfréd; Tscharntke, Teja; Batáry, Péter

    2012-11-01

    Landscape-scale agricultural intensification has caused severe declines in biodiversity. Hedges and forest remnants may mitigate biodiversity loss by enhancing landscape heterogeneity and providing habitat to a wide range of species, including birds. However, nest predation, the major cause of reproductive failure of birds, has been shown to be higher in forest edges than in forest interiors. Little is known about how spatial arrangement (configuration) of hedges affects the avian nest predation. We performed an experiment with artificial ground and elevated nests (resembling yellowhammer and whitethroat nests) baited with quail and plasticine eggs. Nests were placed in three habitat types with different degrees of isolation from forests: forest edges, hedges connected to forests and hedges isolated from forests. Nest predation was highest in forest edges, lowest in hedges connected to forests and intermediate in isolated hedges. In the early breeding season, we found similar nest predation on ground and elevated nests, but in the late breeding season nest predation was higher on ground nests than on elevated nests. Small mammals were the main predators of ground nests and appeared to be responsible for the increase in predation from early to late breeding season, whereas the elevated nests were mainly depredated by small birds and small mammals. High predation pressure at forest edges was probably caused by both forest and open-landscape predators. The influence of forest predators may be lower at hedges, leading to lower predation pressure than in forest edges. Higher predation pressure in isolated than connected hedges might be an effect of concentration of predators in these isolated habitats. We conclude that landscape configuration of hedges is important in nest predation, with connected hedges allowing higher survival than isolated hedges and forest edges.

  11. Tests of landscape influence: Nest predation and brood parasitism in fragmented ecosystems

    Science.gov (United States)

    Tewksbury, J.J.; Garner, L.; Garner, S.; Lloyd, J.D.; Saab, V.; Martin, T.E.

    2006-01-01

    The effects of landscape fragmentation on nest predation and brood parasitism, the two primary causes of avian reproductive failure, have been difficult to generalize across landscapes, yet few studies have clearly considered the context and spatial scale of fragmentation. Working in two river systems fragmented by agricultural and rural-housing development, we tracked nesting success and brood parasitism in >2500 bird nests in 38 patches of deciduous riparian woodland. Patches on both river systems were embedded in one of two local contexts (buffered from agriculture by coniferous forest, or adjacent to agriculture), but the abundance of agriculture and human habitation within 1 km of each patch was highly variable. We examined evidence for three models of landscape effects on nest predation based on (1) the relative importance of generalist agricultural nest predators, (2) predators associated with the natural habitats typically removed by agricultural development, or (3) an additive combination of these two predator communities. We found strong support for an additive predation model in which landscape features affect nest predation differently at different spatial scales. Riparian habitat with forest buffers had higher nest predation rates than sites adjacent to agriculture, but nest predation also increased with increasing agriculture in the larger landscape surrounding each site. These results suggest that predators living in remnant woodland buffers, as well as generalist nest predators associated with agriculture, affect nest predation rates, but they appear to respond at different spatial scales. Brood parasitism, in contrast, was unrelated to agricultural abundance on the landscape, but showed a strong nonlinear relationship with farm and house density, indicating a critical point at which increased human habitat causes increased brood parasitism. Accurate predictions regarding landscape effects on nest predation and brood parasitism will require an

  12. Interactions between multiple recruitment drivers: post-settlement predation mortality and flow-mediated recruitment.

    Directory of Open Access Journals (Sweden)

    Antony M Knights

    Full Text Available BACKGROUND: Dispersal is a primary driver in shaping the future distribution of species in both terrestrial and marine systems. Physical transport by advection can regulate the distance travelled and rate of propagule supply to a habitat but post-settlement processes such as predation can decouple supply from recruitment. The effect of flow-mediated recruitment and predation on the recruitment success of an intertidal species, the eastern oyster Crassostrea virginica was evaluated in two-replicated field experiments. Two key crab species were manipulated to test predator identity effects on oyster mortality. FINDINGS: Recruitment was ∼58% higher in high flow compared to low flow, but predation masked those differences. Predation mortality was primarily attributed to the blue crab Callinectes sapidus, whilst the mud crab Panopeus herbstii had no effect on recruit mortality. Recruit mortality from predation was high when recruit densities were high, but when recruit density was low, predation effects were not seen. Under high recruitment (supply, predation determined maximum population size and in low flow environments, recruitment success is likely determined by a combination of recruitment and resource limitation but not predation. CONCLUSIONS: Four processes are demonstrated: (1 Increases in flow rate positively affect recruitment success; (2 In high flow (recruitment environments, resource availability is less important than predation; (3 predation is an important source of recruit mortality, but is dependent upon recruit density; and (4 recruitment and/or resource limitation is likely a major driver of population structure and functioning, modifying the interaction between predators and prey. Simultaneous testing of flow-mediated recruitment and predation was required to differentiate between the role of each process in determining population size. Our results reinforce the importance of propagule pressure, predation and post

  13. Predator-induced changes of female mating preferences: innate and experiential effects

    Directory of Open Access Journals (Sweden)

    Indy Jeane

    2011-07-01

    Full Text Available Abstract Background In many species males face a higher predation risk than females because males display elaborate traits that evolved under sexual selection, which may attract not only females but also predators. Females are, therefore, predicted to avoid such conspicuous males under predation risk. The present study was designed to investigate predator-induced changes of female mating preferences in Atlantic mollies (Poecilia mexicana. Males of this species show a pronounced polymorphism in body size and coloration, and females prefer large, colorful males in the absence of predators. Results In dichotomous choice tests predator-naïve (lab-reared females altered their initial preference for larger males in the presence of the cichlid Cichlasoma salvini, a natural predator of P. mexicana, and preferred small males instead. This effect was considerably weaker when females were confronted visually with the non-piscivorous cichlid Vieja bifasciata or the introduced non-piscivorous Nile tilapia (Oreochromis niloticus. In contrast, predator experienced (wild-caught females did not respond to the same extent to the presence of a predator, most likely due to a learned ability to evaluate their predators' motivation to prey. Conclusions Our study highlights that (a predatory fish can have a profound influence on the expression of mating preferences of their prey (thus potentially affecting the strength of sexual selection, and females may alter their mate choice behavior strategically to reduce their own exposure to predators. (b Prey species can evolve visual predator recognition mechanisms and alter their mate choice only when a natural predator is present. (c Finally, experiential effects can play an important role, and prey species may learn to evaluate the motivational state of their predators.

  14. 76 FR 50813 - Major Capital Investment Projects; Guidance on News Starts/Small Starts Policies and Procedures

    Science.gov (United States)

    2011-08-16

    ... Federal Transit Administration Major Capital Investment Projects; Guidance on News Starts/Small Starts... policy guidance on the New and Small Starts capital project review and evaluation process and criteria...) published by FTA in June 2010, which sought public comment on the New Starts and Small Starts project...

  15. Is the reaction to chemical cues of predators affected by age or experience in fire salamanders (Salamandra salamandra)

    NARCIS (Netherlands)

    Ibanez, A.; Caspers, B.A.; Lopez, P.; Martin, J.; Krause, E.T.

    2014-01-01

    Predation is one of the strongest forces driving natural selection. Predator success reduces future prey fitness to zero. Thus, recognition and avoidance of a potential predator is an essential fitness-relevant skill for prey. Being well equipped in the predator-prey arms race is highly adaptive. In

  16. Different nest predator faunas and nest predation risk on ground and shrub nests at forest ecotones: an experiment and a review.

    Science.gov (United States)

    Söderström, Bo; Pärt, Tomas; Rydén, Johan

    1998-11-01

    This study examined predator faunas of artificial ground and shrub nests and whether nest predation risk was influenced by nest site, proximity to forest edge, and habitat structure in 38 grassland plots in south-central Sweden. There was a clear separation of predator faunas between shrub and ground nests as identified from marks in plasticine eggs. Corvids accounted for almost all predation on shrub nests whereas mammals mainly depredated ground nests. Nest predation risk was significantly greater for shrub than for ground nests at all distances (i.e. 0, 15 and 30 m) from the forest edge. However, nest predation risk was not significantly related to distance to forest edge, but significantly increased with decreasing distance to the nearest tree. Different corvid species robbed nests at different distances from the forest edge, with jays robbing nests closest to edges. We conclude that the relationship between the predation risk of grassland bird nests and distance to the forest edge mainly depends on the relative importance of different nest predator species and on the structure of the forest edge zone. A review of published articles on artificial shrub and ground nest predation in the temperate zone corroborated the results of our own study, namely that shrub nests experienced higher rates of depredation in open habitats close to the forest edge and that avian predators predominantly robbed shrub nests. Furthermore, the review results showed that predation rates on nests in general are highest <50 m inside the forest and lower in open as well as forest interior habitats (≥50 m from the edge).

  17. Preliminary Estimates of Loss of Juvenile Anadromous Salmonids to Predators in John Day Reservoir and Development of a Predation Model : Interim Report, 1986.

    Energy Technology Data Exchange (ETDEWEB)

    Rieman, Bruce E.

    1986-03-01

    We made preliminary estimates of the loss of juvenile salmonids to predation by walleye, Stizostedion v. vitreum, and northern squawfish, Ptychocheilus oregonensis, in John Day Reservoir in 1984 and 1985 using estimates of predator abundance and daily prey consumption rates. Preliminary estimates may be biased and may be adjusted as much as 30%, but indications are that predation could account for the majority of unexplained loss of juvenile salmonids in John Day Reservoir. Total loss was estimated at 4.1 million in 1984 and 3.3 million in 1985. Northern squawfish consumed 76% and 92% of these totals, respectively. The majority of loss occurred in mid reservoir areas, but loss in a small area, the boat-restricted zone immediately below McNary Dam, was disproportionately large. Peaks in loss in May and July corresponded with peaks in availability of salmonids. Estimated mortality from predation for April through June in 1984 and 1985 was 9% and 7% respectively, for chinook salmon, Oncorhynchus tshawytscha, and 10% and 15% for steelhead, Salmogairdneri. Mortality was variable with time but tended to increase over the period of migration. Mortality of chinook was estimated at 26% to 55% during July and August. A model of predation in John Day Reservoir is outlined. The model includes a predation submodel that can calculate loss from predator number and consumption rate; a population submodel that can relate predator abundance and population structure to recruitment, exploitation, natural mortality and growth; and a distribution submodel that can apportion predators among areas of the reservoir over time. Applications of the model are discussed for projecting expected changes in predation over time and identifying management alternatives that might limit the impact of predation.

  18. Nutrient regulation in a predator, the wolf spider Pardosa prativaga

    DEFF Research Database (Denmark)

    Jensen, Kim; Mayntz, David; Toft, Søren

    2011-01-01

    Nutrient balancing is well known in herbivores and omnivores, but has only recently been demonstrated in predators. To test how a predator might regulate nutrients when the prey varies in nutrient composition, we restricted juvenile Pardosa prativaga wolf spiders to diets of one of six fruit fly......, Drosophila melanogaster, prey types varying in lipid:protein composition during their second instar. We collected all fly remnants to estimate food and nutrient intake over each meal. The spiders adjusted their capture rate and nutrient extraction in response to prey mass and nutrient composition...... irrespective of energy intake. Intake was initially regulated to a constant lipid plus protein mass, but later spiders fed on prey with high proportions of protein increased consumption relative to spiders fed on other prey types. This pattern indicates that the spiders were prepared to overconsume vast...

  19. Predator deterrence by mandibular gland secretions of bees (Hymenoptera: Apoidea).

    Science.gov (United States)

    Cane, J H

    1986-06-01

    Volatile lipids from the mandibular gland secretions of bees (Hymenoptera: Apoidea) are potent olfactory repellents of foraging ants (Formica, Crematogaster) in biologically relevant contexts and quantities. In contrast, differential success in capture of bee and fly prey by predatory asilid flies (Efferia), reduviid bugs (Apiomerus), and arachnids (Agelenopsis, Argiope) is better explained by prey size than by chemical repellence, aposematism, or possession of a sting. Supernormal doses of some allomones, applied to worker honeybees (Apis mellifera) that were fed toArgiope aurantia spiders, elicted more frequent preenvenomation pauses following ensnarement but did not significantly increase other prey-handling times. These pauses merely delayed the bee's demise. Mandibular gland secretions of solitary bees augment their other secondary defenses in at least two contexts: (1) during intranest encounters when repelling intruding ants, and (2) retaliation delivered to their arthropodan predators which, if the bee is nearly too large for the predator to handle, may allow the bee to escape.

  20. Bifurcation Behavior Analysis in a Predator-Prey Model

    Directory of Open Access Journals (Sweden)

    Nan Wang

    2016-01-01

    Full Text Available A predator-prey model is studied mathematically and numerically. The aim is to explore how some key factors influence dynamic evolutionary mechanism of steady conversion and bifurcation behavior in predator-prey model. The theoretical works have been pursuing the investigation of the existence and stability of the equilibria, as well as the occurrence of bifurcation behaviors (transcritical bifurcation, saddle-node bifurcation, and Hopf bifurcation, which can deduce a standard parameter controlled relationship and in turn provide a theoretical basis for the numerical simulation. Numerical analysis ensures reliability of the theoretical results and illustrates that three stable equilibria will arise simultaneously in the model. It testifies the existence of Bogdanov-Takens bifurcation, too. It should also be stressed that the dynamic evolutionary mechanism of steady conversion and bifurcation behavior mainly depend on a specific key parameter. In a word, all these results are expected to be of use in the study of the dynamic complexity of ecosystems.

  1. Wolf predation in the Burwash caribou herd, southwest Yukon

    Directory of Open Access Journals (Sweden)

    David A. Gauthier

    1986-06-01

    Full Text Available The role of wolf predation as a proximate mortality factor influencing caribou herd growth was assessed in the Burwash herd (400 animals in the southwest Yukon between 1980 - 1982. Ten to 14 wolves in two packs preyed primarily on caribou (Rangifer tarandus caribou and moose (Alces alces with disproportionate consumption of caribou (relative to available biomass in the rut and winter periods. Wolf predation was responsible for 72% of total annual mortality in 1980 - 1981 and 46% in 1981 - 1982. Losses due to human harvest varied between 7 to 13%. Additional limited data on climatic factors and winter forage indicated forage-climate were not major proximate mortality factors in 1980 - 1981, but that early-calving climate may have been a factor in increased calf mortality in 1982.

  2. Sea urchins, their predators and prey in SW Portugal

    Directory of Open Access Journals (Sweden)

    Nuno Mamede

    2014-06-01

    Full Text Available Sea urchins play a key role structuring benthic communities of rocky shores through an intense herbivory. The most abundant sea urchin species on shallow rocky subtidal habitats of the SW coast of Portugal is Paracentrotus lividus (Echinodermata: Echinoidea. It is considered a key species in various locations throughout its geographical distribution by affecting the structure of macroalgae communities and may cause the abrupt transformation of habitats dominated by foliose algae to habitats dominated by encrusting algae - the urchin barrens. The removal of P. lividus predators by recreational and commercial fishing is considered a major cause of this phenomenon by affecting the trophic relationships between predators, sea urchins and algae communities. Marine protected areas (MPAs usually lead to the recovery of important predator species that control sea urchin populations and restore habitats dominated by foliose macroalgae. Therefore, MPAs provide a good opportunity to test cascading effects and indirect impacts of fishing at the ecosystem level. The ecological role of P. lividus was studied on rocky subtidal habitats of the SW coast of Portugal (Alentejo considering three trophic levels: population of P. lividus, their predators (fish and shellfish and their prey (macroalgae communities. Several studies were conducted: (1 a non-destructive observational study on the abundance and distribution patterns of P. lividus, their predators and preys, comparing areas with different protection; (2 a manipulative in situ study with cages to assess the role of P. lividus as an herbivore and the influence of predation; (3 a descriptive study of P. lividus predators based on underwater filming; (4 and a study of human perception on these trophic relationships and other issues on sea urchin ecology and fishery, based on surveys made to fishermen and divers. Subtidal studies were performed with SCUBA diving at 3-12 m deep. Results indicate that in the

  3. Parasitism, predation and the evolution of animal personalities.

    Science.gov (United States)

    Kortet, Raine; Hedrick, Ann V; Vainikka, Anssi

    2010-12-01

    Trade-offs between behavioural traits promoting high life-history productivity and mortality may fuel the evolution of animal personalities. We propose that parasites, including pathogens, impose fitness costs comparable to those from predators, and influence the adaptiveness of personality traits associated with productivity (PAPs). Whether personality traits are adaptive or not may also depend on individual immunological capacity. We illustrate this using a conceptual example in which the optimal level of PAPs depends on predation, parasitism and host compensation (resistance and tolerance) of parasitism's negative effects. We assert that inherent differences in host immune function can produce positive feedback loops between resource intake and compensation of parasitism's costs, thereby providing variation underlying the evolution of stable personalities. Our approach acknowledges the condition dependence of immune function and co-evolutionary dynamics between hosts and parasites. © 2010 Blackwell Publishing Ltd/CNRS.

  4. Grey seal predation on forage fish in the Baltic Sea

    DEFF Research Database (Denmark)

    Eero, Aro; Neuenfeldt, Stefan; Aho, Teija

    has increased accordingly. The diet of grey seal in the Baltic consists of ca. 20 fish species. The most abundant prey items in the Baltic proper are Baltic herring, sprat, and cod, and in the Bothnian Sea and Bothnian Bay Baltic herring, Coregonus sp., Baltic salmon, and sea trout. An adult seal...... consumes on average round 4.5 kg fish per day, of which 55% are clupeoids in the Baltic Main basin and 70% in the Bothnian Sea and Bothnian Bay. According to acoustic estimates, predator– prey distribution patterns, migration patterns, and multispecies analysis (SMS), the predation effect of grey seals...... on Baltic herring and sprat stocks is still at a very low level. Hence, with present grey seal stock sizes, the impact of seal predation can be ignored in whole Baltic‐scale herring and sprat stock management considerations. Locally, however, grey seal–fishery interactions play an important role and should...

  5. Industrial melanism in Biston betularia: the role of selective predation

    Energy Technology Data Exchange (ETDEWEB)

    Lees, D.R.; Creed, E.R.

    1975-02-01

    A large amount of information is available on the distribution of the melanic morphs of B. betularia in Britain. High melanic frequencies are associated with areas of intense air pollution but are also found in parts of eastern England which are relatively unpolluted. In order to ascertain whether bird predation could account for these high frequencies, it was decided to carry out a predation experiment in East Anglia where it was found that, apart from a possible decrease in foliose lichen cover, the trees were little affected by atmospheric pollution and their bark was generally light in color. A similar experiment was conducted in the wood near the heavily industrialized Birmingham conurbation; this provided a control and a direct comparison with earlier results. 35 references.

  6. Power plant start-up demands productive methods and practices

    Energy Technology Data Exchange (ETDEWEB)

    Follett, R.E.

    1993-05-01

    This article examines the factors affecting power plant start-up. The article addresses cogeneration plants in particular. The topics of the article include the start-up schedule, start-up program administration, safety tagging procedure, system boundary identification, mechanical test procedures, electrical test procedures, pre-operational tests, loop calibration reports, performance test procedure, instrument calibration, checkout philosophy, plant start-up organization, plant start-up sequence, operator training, and typical plant start-up conditions.

  7. Take Control of Getting Started with Dreamweaver

    CERN Document Server

    Keller, Arnie

    2009-01-01

    Learn fundamental Web design principles and become comfortable working in Dreamweaver's complex interface! Dreamweaver 8 is a great Web design tool for pros, but newcomers may be overwhelmed by its interface or want to know more about how to work creatively and intelligently in the program. Help is at hand in Take Control of Getting Started with Dreamweaver, which offers a detailed tutorial for making your first site in Dreamweaver. Author Arnie Keller, who teaches Web design at the University of Victoria, shows you how to style type the smart way with CSS, create a sophisticated page layout

  8. Getting started with Zurb Foundation 4

    CERN Document Server

    Patterson, Andrew D

    2013-01-01

    The book starts with the basics of Foundation and helps you build your skills as you advance from installation to design, configuration, and customization with examples at every step.This book will be of great benefit to web architects, designers, and builders. While it helps to be a programmer, it isn't necessary for this book. You should be familiar with the basic principles of responsive web design and have a desire to create a professional website that looks great on both mobile devices and regular displays.

  9. Getting started with the Lazarus IDE

    CERN Document Server

    Person, Roderick

    2013-01-01

    This book is written in a simple, easy-to-understand format with lots of screenshots and step-by-step explanations.This book is geared toward developers that have a familiarity with Delphi or Free Pascal and would like to start using the open source Lazarus Integrated Development Environment. You should have knowledge of creating a console and GUI applications as well as creating basic components. Example source code and projects are provided to help learn the differences between Delphi and Lazarus projects.

  10. Getting started with ownCloud

    CERN Document Server

    Patawari, Aditya

    2013-01-01

    This is a standard, precise, and short tutorial for setting up ownCloud and includes advanced topics like encryption, user management, and server security. This ownCloud book would be an ideal starting point for anyone who wants to store their data and also share it.This book is for first time users as well as administrators who are interested or responsible for managing an ownCloud instance. You do not need any prior experience with any of the technology, including Linux/Windows, Apache/IIS, SQLite/MySQL, or even PHP. It is a beginner-friendly book, written with a first time user in mind.

  11. Successful start-ups & key success factors

    OpenAIRE

    Brillois, Bertrand

    2000-01-01

    Almost everyday we can read about or listen to the radio the creation of a new company, which is of course successfull and just started several months ago. One succeed but for how many other failures. In our everyday life we only know the companies which exist. We never consider all the high number of companies that have failed. In addition to that, by analyzing some cases, we can notice that some"good"companies, with good team, good concept can failed too. In order to understand the views th...

  12. Start your own information marketing business

    CERN Document Server

    Skrob, Robert

    2013-01-01

    Breaking down the information marketing world from A to Z, the undisputed info marketing expert offers professional strategies to set up a successful information marketing business. These businesses are easy to start, can be run from home, don't require any employees, need little cash outlay, can be run part-time, and can produce millions of dollars a year. Readers learn everything they need to jump into this lucrative field, creating an entirely new business that gives them added income or replaces their current salary entirely.

  13. Getting started with FortiGate

    CERN Document Server

    Fabbri, Rosato

    2013-01-01

    This book is a step-by-step tutorial that will teach you everything you need to know about the deployment and management of FortiGate, including high availability, complex routing, various kinds of VPN working, user authentication, security rules and controls on applications, and mail and Internet access.This book is intended for network administrators, security managers, and IT pros. It is a great starting point if you have to administer or configure a FortiGate unit, especially if you have no previous experience. For people that have never managed a FortiGate unit, the book helpfully walks t

  14. Getting started in 3D with Maya

    CERN Document Server

    Watkins, Adam

    2012-01-01

    Deliver professional-level 3D content in no time with this comprehensive guide to 3D animation with Maya. With over 12 years of training experience, plus several award winning students under his belt, author Adam Watkins is the ideal mentor to get you up to speed with 3D in Maya. Using a structured and pragmatic approach Getting Started in 3D with Maya begins with basic theory of fundamental techniques, then builds on this knowledge using practical examples and projects to put your new skills to the test. Prepared so that you can learn in an organic fashion, each chapter builds on the know

  15. EU Emission Trading: Starting with Carbon Dioxide

    DEFF Research Database (Denmark)

    Vesterdal, Morten; Svendsen, Gert Tinggaard

    2003-01-01

    The Commission of the European Union wants to start a limited emission trading scheme by 2005 within the Community to enable "learning-by-doing" prior to the Kyoto Protocol. This to accomplish the desired 8% target level for six different greenhouse gases. However, in the EU it is not clear whether...... all the six relevant greenhouse gases or only CO2 should be traded. What is the simplest and most practicable solution? We argue in favour of the latter option for three main reasons: the possible dominating global warming potential of CO2, expected future developments in CO2 emissions and the fact...

  16. Do top predators cue on sound production by mesopelagic prey?

    Science.gov (United States)

    Baumann-Pickering, S.; Checkley, D. M., Jr.; Demer, D. A.

    2016-02-01

    Deep-scattering layer (DSL) organisms, comprising a variety of mesopelagic fishes, and squids, siphonophores, crustaceans, and other invertebrates, are preferred prey for numerous large marine predators, e.g. cetaceans, seabirds, and fishes. Some of the DSL species migrate from depth during daylight to feed near the surface at night, transitioning during dusk and dawn. We investigated if any DSL organisms create sound, particularly during the crepuscular periods. Over several nights in summer 2015, underwater sound was recorded in the San Diego Trough using a high-frequency acoustic recording package (HARP, 10 Hz to 100 kHz), suspended from a drifting surface float. Acoustic backscatter from the DSL was monitored nearby using a calibrated multiple-frequency (38, 70, 120, and 200 kHz) split-beam echosounder (Simrad EK60) on a small boat. DSL organisms produced sound, between 300 and 1000 Hz, and the received levels were highest when the animals migrated past the recorder during ascent and descent. The DSL are globally present, so the observed acoustic phenomenon, if also ubiquitous, has wide-reaching implications. Sound travels farther than light or chemicals and thus can be sensed at greater distances by predators, prey, and mates. If sound is a characteristic feature of pelagic ecosystems, it likely plays a role in predator-prey relationships and overall ecosystem dynamics. Our new finding inspires numerous questions such as: Which, how, and why have DSL organisms evolved to create sound, for what do they use it and under what circumstances? Is sound production by DSL organisms truly ubiquitous, or does it depend on the local environment and species composition? How may sound production and perception be adapted to a changing environment? Do predators react to changes in sound? Can sound be used to quantify the composition of mixed-species assemblages, component densities and abundances, and hence be used in stock assessment or predictive modeling?

  17. Parthenocarpy and seed predation by insects in Bursera morelensis.

    Science.gov (United States)

    Ramos-Ordoñez, María F; Márquez-Guzmán, Judith; Del Coro Arizmendi, Ma

    2008-11-01

    While parthenocarpy (meaning the production of fruits without seeds) may limit fecundity in many plants, its function is not clear; it has been proposed, however, that it might be associated with a strategy to avoid seed predation. Bursera morelensis is a dioecious endemic plant that produces fruits with and without seeds, and its fruits are parasitized by insects. Its reproductive system is not well described and no published evidence of parthenocarpy exists for the species. The purpose of this work was to describe the breeding system of B. morelensis and its relationship to seed predation by insects. The breeding system was described using pollination experiments, verifying the presence of parthenocarpic fruits and apomictic seeds. Reproductive structures from flower buds to mature fruits were quantified. For fruits, an anatomical and histological characterization was made. The number of fruits in which seeds had been predated by insects was correlated with parthenocarpic fruit production. The major abortion of reproductive structures occurred during fruit set. The results discard the formation of apomictic seeds. Flowers that were not pollinated formed parthenocarpic fruits and these could be distinguished during early developmental stages. In parthenocarpic fruits in the first stages of development, an unusual spread of internal walls of the ovary occurred invading the locule and preventing ovule development. Unlike fruits with seeds, parthenocarpic fruits do not have calcium oxalate crystals in the ovary wall. Both fruit types can be separated in the field at fruit maturity by the presence of dehiscence, complete in seeded and partial in parthenocarpic fruits. Trees with more parthenocarpic fruits had more parasitized fruits. This is the first time the anatomy of parthenocarpic fruits in Burseraceae has been described. Parthenocarpic fruits in B. morelensis might function as a deceit strategy for insect seed predators as they are unprotected both chemically

  18. Predation and selection for antibiotic resistance in natural environments

    DEFF Research Database (Denmark)

    Leisner, Jørgen; Jørgensen, Niels O. G.; Middelboe, Mathias

    2016-01-01

    Genes encoding resistance to antibiotics appear, like the antibiotics themselves, to be ancient, originating long before the rise of the era of anthropogenic antibiotics. However, detailed understanding of the specific biological advantages of antibiotic resistance in natural environments is still......, predation is potentially an important mechanism for driving antibiotic resistance during slow or stationary phase of growth when nutrients are deprived. This adds to explain the ancient nature and widespread occurrence of antibiotic resistance in natural environments unaffected by anthropogenic antibiotics...

  19. Autumn predation of northern red oak seed crops

    Science.gov (United States)

    Kim C. Steiner

    1995-01-01

    Production and autumn predation of northern red oak acorns was measured over four years in five Pennsylvania stands dominated by this species. Mean annual production was 41,779/acre, of which an average of 7.9% was destroyed by insects or decay following insect attack, and an average of 38.6% was destroyed or removed by vertebrates. White-tailed deer appeared to be the...

  20. Cascade of complexity in evolving predator-prey dynamics.

    Science.gov (United States)

    Guttenberg, Nicholas; Goldenfeld, Nigel

    2008-02-08

    We simulate an individual-based model that represents both the phenotype and genome of digital organisms with predator-prey interactions. We show how open-ended growth of complexity arises from the invariance of genetic evolution operators with respect to changes in the complexity, and that the dynamics which emerges shows scaling indicative of a nonequilibrium critical point. The mechanism is analogous to the development of the cascade in fluid turbulence.