Dissertations / Theses: 'Predator of'

1

Garza, Mark Isaac. "Predator induced defenses in prey with diverse predators." Texas A&M University, 2005. http://hdl.handle.net/1969.1/3309.

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Phenotypic plasticity is an environmentally based change in phenotype and can be adaptive. Often, the change in an organism's phenotype is induced by the presence of a predator and serves as a defense against that predator. Defensive phenotypes are induced in freshwater physid snails in response to both crayfish and molluscivorous fish. Alternative morphologies are produced depending on which of these two predators snails are raised with, thus protecting them from each of these predators' unique mode of predation. Snails and other mollusks have been shown to produce thicker, differently shaped shells when found with predators relative to those found without predators. This production of thicker, differently shaped shells offers better protection against predators because of increased predator resistance. The first study in this thesis explores costs and limits to plasticity using the snailfish- crayfish system. I exposed juvenile physid snails (using a family structure) to either early or late shifts in predation regimes to assess whether developmental flexibility is equally possible early and late in development. Physid snails were observed to produce alternative defensive morphologies when raised in the presence of each of the two predators. All families responded similarly to the environment in which they were raised. Morphology was found to be heritable, but plasticity itself was not heritable. Morphology was found to become less flexible as snails progressed along their respective developmental pathways. In the second study, I raised physid snails with and without shell-crushing sunfish and examined the differences in shell thickness, shell mass, shell size and shell microstructural properties between the two treatment groups. Shells of snails raised with predators were found to be larger, thicker and more massive than those raised without predators, but differences in microstructure were found to be insignificant. I conclude that the observed shell thickening is accomplished by the snails' depositing more of the same material into their shells and not by producing a more complex shell composition.

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2

Powell, Adam. "Predation and scavenging by the generalist predator, Pterostichus melanarius." Thesis, Cardiff University, 2011. http://orca.cf.ac.uk/54182/.

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The research reported in this thesis investigated the ability of P. melanarius to control slug populations, and the impacts that alternative prey, particularly carrion, has on the efficacy of this predator as an agent of slug pest control. A suite of laboratory- and field-based experiments were conducted to achieve those ends. The main findings were: (1) Prey vital status was significant in determining the feeding preference hierarchy of P. melanarius. The mucus defence of live slugs (Deroceras reticulatum) deterred attacks by beetles, but feeding on dead D. reticulatum emphasized a preference for this prey type by P. melanarius. (2) The survival rate of D. reticulatum bitten by P. melanarius was not different to that of non-attacked control slugs. Attacking bites by P. melanarius, visited upon live slugs, did not yield slug DNA-positive results during molecular analysis of beetle foregut contents. (3) Pterostichus melanarius was not able to detect by olfaction the presence of live or 12 h-decayed dead D. reticulatum. (4) The feeding history of P. melanarius had a significant influence on subsequent prey selection. However, the effect interacted with an innate, overarching prey preference hierarchy. (5) A large-scale semi-field experiment identified that P. melanarius fed upon slugs, but the effect of predation pressure was not sufficient to induce negative growth in slug population density. The presence of alternative prey, and the increasing mass of individual slugs exerted rate-limiting effects on slug-predation by P. melanarius.

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3

Bolohan, Noah. "Seasonal Variation in a Predator-Predator-Prey Model." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/40899.

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Seasonal shifts in predation habits, from a generalist in the summer to a specialist in the winter, have been documented for the great horned owl (Bulbo virginialis) in the boreal forest. This shift occurs largely due to varying prey availability. There is little study of this switching behaviour in the current literature. Since season length is predicted to change under future climate scenarios, it is important to understand resulting effects on species dynamics. Previous work has been done on a two-species seasonal model for the great horned owl and its focal prey, the snowshoe hare (Lepus americanus). In this thesis, we extend the model by adding one of the hare's most important predators, the Canadian lynx (Lynx canadensis). We study the qualitative behaviour of this model as season length changes using tools and techniques from dynamical systems. Our main approach is to determine when the lynx and the owl may invade the system at low density and ask whether mutual invasion of the predators implies stable coexistence in the three-species model. We observe that, as summer length increases, mutual invasion is less likely, and we expect to see extinction of the lynx. However, in all cases where mutual invasion was satisfied, the three species stably coexist.

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Connors, Matthew J. "Quantifying spatial and temporal heterogeneity in predator activity and predation risk /." Available to subscribers only, 2005. http://proquest.umi.com/pqdweb?did=1104973781&sid=3&Fmt=2&clientId=1509&RQT=309&VName=PQD.

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5

Bodey, T. W. "Impacts of predator manipulations on island predator and prey populations." Thesis, Queen's University Belfast, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515898.

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6

Griswold, Marcus W. "Predator-mediated coexistence and multiple predator effects in a treehole community." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0004288.

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McKnight, Julie L. "Predator and prey population dynamics and distribution, effects of predation and competition." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ58428.pdf.

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8

Burgener, Joel Ryan. "Predation on meadow voles: predator response to vole abundance and vole response to predator exclusion in Red Rock Lakes National Wildlife Refuge, Montana." Montana State University, 2011. http://etd.lib.montana.edu/etd/2011/burgener/BurgenerJ0811.pdf.

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Small mammals such as meadow voles exhibit complex and puzzling multi-annual population cycles. Predators can have an effect on these cycles though the precise relationship is not completely understood. I undertook this study to 1) quantify the response of predators to small mammal abundance and 2) determine the relative roles of mammalian meso-predators and raptors on abundance and survivorship of small mammals in wet meadow habitat at Red Rock Lakes National Wildlife Refuge, southwest Montana. as well as the response by predators to different levels of small mammal abundance. Two randomly placed trapping grids were placed inside three adjacent grazing units. Two additional treatment trapping grids were placed inside one of the grazing units with an electrified polywire fence to exclude mesopredators. The trapping occurred in July and August of 2010 on the Refuge. The trapping occurred in three primary sessions with four individual trapping days (secondary sessions) per primary session in each grazing unit. Predators were monitored by conducting visual raptor surveys and camera trapping. My results indicated that partial predator exclusion did not improve vole survivorship in fact some raptors used the fence posts as supplemental perches, as some bore signs of use. My results also did not support the hypothesis that raptor abundance tracked vole abundance. However, vole abundance was significantly higher during 2010 than in previous years. The increase in vole abundance resulted in other factors driving habitat selection by raptors. The camera traps did not provide any information about the use of the wet meadow by mammalian predators, however other signs of mammalian predators were observed in the trapping area during the study. Further study may shed more light on the use of supplemental perches by raptors and how mammalian predators are using the wet meadow habitat on the Refuge.

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9

Lewis, Danny. "Effects of abiotic stress and predator refuge on terrestrial predator-prey interactions." College Park, Md.: University of Maryland, 2009. http://hdl.handle.net/1903/9125.

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Thesis (Ph. D.) -- University of Maryland, College Park, 2009.
Thesis research directed by: Dept of Entomology. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

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Connolly, Lauren E. "Effect of predator diet on foraging behavior of panopeus herbstII in response to predator urine cues." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/53392.

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The ability of prey to detect and respond appropriately to predator risk is important to overall prey fitness. Many aquatic organisms assess risk through the use of chemical cues that can change with predator diet. Two variable characteristics of diet are: 1. prey type and 2. prey mass. To assess the effect of these two characteristics on the assessment of risk by the mud crab Panopeus herbstii, I exposed mud crabs to the urine of the blue crab Callinectes sapidus fed one of 5 diet treatments: 10g of oyster shell free wet mass, 5g of oyster shell free wet mass, 10g crushed mud crabs, 5g crushed mud crabs, and a mix of 5g of oyster shell free wet mass and 5g crushed mud crab. Effects on P. herbstii foraging were tested in a previously developed bioassay by measuring shrimp consumption over a 4 hour period. I hypothesized that P. herbstii would have a larger magnitude response to urine from C. sapidus fed a diet of crushed mud crabs than to urine from C. sapidus fed a diet of oysters. I further hypothesized that P. herbstii would have a larger magnitude response to urine from C. sapidus fed a high mass diet relative to a lower mass diet. Contrary to expectations there was no observed effect of urine on P. herbstii foraging in any of the treatments. Results suggest that bioassay protocol may be unreliable suggesting further replication to determine the difference between this study and previous results. Future studies examining how P. herbstii varies with urine concentration will aid in understanding the ecological scale of this predator cue system. Determining the role of other potential cue sources will improve the predictive abilities of these studies.

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Hiorth, Ole Henrik, and Jan Kristian Borgen. "Return of Predator X." Thesis, Norges teknisk-naturvitenskapelige universitet, Fakultet for arkitektur og billedkunst, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13798.

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12

Brouillette, Amber Noelle. "Sex-Biased Predation on Taricha by a Novel Predator in Annadel State Park." DigitalCommons@USU, 2008. https://digitalcommons.usu.edu/etd/111.

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Newts of the genus Taricha have long been studied due to the powerful neurotoxin found in their skin. Tetrodotoxin (TTX) acts by blocking receptors in sodium channels, ultimately resulting in death via asphyxiation. The only documented predators of species in this genus have been snakes of the genus Thamnophis. Recently, predation on Taricha in Ledson Marsh in Annadel State Park, Santa Rosa, CA was discovered. Predation was in the form of laceration or evisceration, and tracking of predation from 1998-2008 showed that it was male-biased. Two species of Taricha were found living sympatrically at this location, the California newt (T. torosa) and the rough-skinned newt (T. granulosa). Fluorometric High Phase Liquid Chromatography (HPLC) analysis was used in order to quantify TTX levels in the skin of ten male and ten female newts of each species. Quantification of TTX was done to determine the influence, if any, that TTX levels may have on sex-biased predation in this population. I predicted that levels of TTX would be greater in females than males, and greater in T. granulosa than T. torosa since very few T. granulosa were preyed upon during the study period. My results indicated that there were significant differences between the sexes, and T. torosa were significantly more toxic than T. granulosa. An in-depth ecological study of relative abundances of both species and identification of the predator are needed at this site to obtain a clear picture of the predator-prey dynamics at Ledson Marsh

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13

Wrinn, Kerri M. "Impacts of an herbicide and predator cues on a generalist predator in agricultural systems." Oxford, Ohio : Miami University, 2010. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=miami1272569523.

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14

Carlson, Nora. "Anti-predator behaviour in UK tit species : information encoding, predator recognition, and individual variation." Thesis, University of St Andrews, 2017. http://hdl.handle.net/10023/11366.

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To combat the ever-present threat of predation many species produce anti-predator vocalizations and behaviours (mobbing) designed to drive predators away. These vocalizations can encode a predator's threat level, and many species within a community will eavesdrop on this information. To determine how prey species produce, use, and respond to anti-predator information and how individual, social, and phylogenetic factors of different species may influence this behaviour, I conducted a series of robotic-predator presentation and anti-predator vocalization playback experiments in the wild and lab. I predicted that UK Paridae would encode information the same as previously studied species. I found that UK Paridae encode predator information in different ways, and that neither phylogeny nor ecology explained the patterns of similarity in how different species encode predator threat in their calls. Flock structure appeared to affect how species encoded predator threat and while multiple species may be sources of information for familiar flock mates, only blue and great tits met the criteria to be community informants. As blue and great tits need prior experience to recognize novel predators and juvenile great tits avoid novel predators only after seeing adults mob them, tits may use mobbing calls to learn about novel predators. While they responded to mobbing calls, juvenile blue and great tits did not engage in mobbing behaviour although they appear capable of doing so. Furthermore, while individuals varied in their responses to aerial alarm calls this variation was not explained by either their proximity to the call nor their personality. In this close examination of how anti-predator vocalizations are produced and used by UK Paridae, I found variation in these signals. This challenges previous assumptions about how Paridae encode information, raising questions as to the sources of this variation.

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15

Funderburk, James. "Modern Variation in Predation Intensity: Constraints on Assessing Predator-Prey Relationships in Paleoecologic Reconstructions." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3491.

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The complex interaction between predators and their prey is rarely preserved in the fossil record. However, predation of marine mollusks by drilling gastropods leaves a diagnostic hole in the shell of the prey, possibly allowing for quantitative analysis of this ecological interaction. Drilling frequency, as measured in marine mollusks both in the Modern and fossil record, has been heralded as a potential opportunity to quantify these ecological interactions and use these values in the testing of hypotheses. This study employed the collection, tallying, and analysis of bulk samples derived from shelly deposits on 45 Modern beaches along the contiguous coast of the southeast United States (Virginia Beach, VA to Port Isabella, TX). The tallying scheme allowed for pooling and reduction of the data to compare drilling frequencies at several taxonomic and geographic scales. In addition, multivariate clustering analyses was used to generate groups of similar taxonomic abundances for direct comparison. Understanding potential spatial variation in the natural environment is paramount to using quantified values of drilling frequency in temporal and spatial studies in the fossil record. Calculated drilling frequencies for bulk (location) samples ranged from 0 to over 100%. Similar ranges of drilling frequency were observed in more finely defined taxonomic groups. Calculated drilling frequency was higher in the Carolinian province as compared to the Gulf-Louisianian and Virginian provinces. No correlation between drilling frequency and latitude was observed at any scale. An area of substantially increased drilling frequency was observed along the Carolina coast, at the ecotone between the Carolinian and Virginian provinces, suggesting that some environmental condition is present and responsible for the local increase in drilling frequency. Finally, little attention has been paid to sampling techniques and their subsequent impact on the analysis of drilling frequency. As the bulk samples represent aggregate accumulations of shells from a myriad of environments, this introduces pronounced variation in the analysis that has not been previously accounted for. Statistically, much larger abundances of specimens in individual taxa, approaching 450 values for bivalves, are needed to effectively constrain this variability.

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Rhisiart, Alun ap. "Communication and anti-predator behaviour." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333182.

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17

Liu, Shouzong. "AGE-STRUCTURED PREDATOR-PREY MODELS." OpenSIUC, 2018. https://opensiuc.lib.siu.edu/dissertations/1577.

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In this thesis, we study the population dynamics of predator-prey interactions described by mathematical models with age/stage structures. We first consider fixed development times for predators and prey and develop a stage-structured predator-prey model with Holling type II functional response. The analysis shows that the threshold dynamics holds. That is, the predator-extinction equilibrium is globally stable if the net reproductive number of the predator $\mathcal{R}_0$ is less than $1$, while the predator population persists if $\mathcal{R}_0$ is greater than $1$. Numerical simulations are carried out to demonstrate and extend our theoretical results. A general maturation function for predators is then assumed, and an age-structured predator-prey model with no age structure for prey is formulated. Conditions for the existence and local stabilities of equilibria are obtained. The global stability of the predator-extinction equilibrium is proved by constructing a Lyapunov functional. Finally, we consider a special case of the maturation function discussed before. More specifically, we assume that the development times of predators follow a shifted Gamma distribution and then transfer the previous model into a system of differential-integral equations. We consider the existence and local stabilities of equilibria. Conditions for existence of Hopf bifurcation are given when the shape parameters of Gamma distributions are $1$ and $2$.

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Lindström, Torsten. "Predator-prey systems and applications." Licentiate thesis, Luleå tekniska universitet, 1991. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25928.

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Brodin, Tomas. "Predator effects on behaviour and life-history of prey." Doctoral thesis, Umeå : Dept. of Ecology and Environmental Science, Univ, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-629.

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20

Rodgers, Brandon. "Poecilia reticulata predation on Aedes aegypti larvae : effects of predator body size and vegetation density." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100206.

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In this study, predation efficiency of three guppy ( Poecilia reticulata) size classes was evaluated at various vegetation densities in a series of circular aquaria containing plastic plants closely resembling Ceratophyllum demersum. The effect of vegetation density was most apparent among large fish where predation efficiency greatly diminished from 12.35 mosquito larvae (Aedes aegypti) to 4.68 as vegetation densities rose from 3 to 19 plants/700 cm2. Over that same range of increasing vegetation densities, predation among small fish remained unchanged, whereas among fish of intermediate size predation declined significantly but less precipitously than for large individuals. When presented with a choice between second and fourth mosquito larvae, small fish preferred to prey on second instars, whereas large fish preferred fourth instar larvae. Fish of intermediate size did not show a statistically significant preference. The functional response of fish to increasing prey densities, as measured over a 12-h period, was of Type III.

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Bromilow, Amanda Marie. "Juvenile Blue Crab Survival in Nursery Habitats: Predator Identification and Predation Impacts in Chesapeake Bay." W&M ScholarWorks, 2017. https://scholarworks.wm.edu/etd/1516639467.

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Predator populations can have significant impacts on prey recruitment success and prey population dynamics through consumption. Young, inexperienced prey are often most vulnerable to predation due to their small size and limited evasion capabilities. to reduce the risk of predation, new recruits and young juveniles typically settle in structured nursery habitats, such as seagrass beds, which promote higher survival by acting as refuges from predators. Thus, successful recruitment to the adult portion of the population is often dependent on the availability of suitable nursery habitat. In this thesis, I used field tethering experiments and gut content analyses to assess the role of habitat, body size, finfish predation, and cannibalism on the survival of one of the most ecologically and economically important species in Chesapeake Bay: the blue crab Callinectes sapidus. In field tethering experiments, survival probability of juvenile blue crabs in York River nursery habitats (i.e. seagrass beds, sand flats) increased significantly and additively with crab size and SAV cover. Images of predation events during tethering experiments revealed cannibalism by adult blue crabs to be a major source of juvenile mortality. Gut content analyses from three field studies identified seven predators of juvenile blue crabs in lower Chesapeake Bay nursery habitats: adult blue crabs, striped bass Morone saxatilis, red drum Sciaenops ocellatus, silver perch Bairdiella chrysoura, weakfish Cynoscion regalis, Atlantic croaker Micropogonias undulatus, and oyster toadfish Opsanus tau. Using frequency of consumption and diet proportion metrics, I determined striped bass, red drum, and silver perch to be the most impactful finfish predators on juvenile mortality, in addition to cannibalism. Atlantic croaker and oyster toadfish play minor roles in juvenile mortality in Chesapeake Bay nursery habitats. The probability of juvenile crabs being present in a predator’s gut was also significantly higher in seagrass beds than in unvegetated sand flats. Food web dynamics are an important aspect of ecosystem-based fisheries management. Understanding the ecological interactions between populations, and their environment, can provide insight into natural population fluctuations of valuable fishery species such as the blue crab. This thesis demonstrated the positive effects of body size and SAV cover on juvenile crab survival, indicating the importance of seagrass nursery habitat for blue crab population dynamics in Chesapeake Bay. However, despite the predator refuge offered by SAV, high densities of predators and prey in seagrass beds resulted in greater consumption of juveniles in those habitats. Key predators of juvenile blue crabs were also identified and their relative impacts were estimated. The predator-prey relationships revealed in this thesis were integrated into a revised food web for blue crabs in Chesapeake Bay, in the hopes of informing future ecosystem-based management efforts.

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El, Balaa Rayan. "Effect of Predator Diet on Predator-induced Changes in Life History and Performance of Anuran Larvae." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/22790.

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Phenotypic plasticity allows some animals to change their behavioural, morphological, performance, and life history traits in response to changes in environmental conditions such as the presence of predators. These changes can enhance survival, but come at a cost. Some of these phenotypic changes are predator and diet specific. I examined the effects of predator diet on the performance, life-history, and morphology of developing Northern Leopard Frog (Lithobates pipiens) tadpoles. Tadpoles were either exposed to cues from fish free water, cues from Brown Bullhead (Ameiurus nebulosus) fed a diet of trout pellets, or cues from A. nebulosus fed a L. pipiens tadpoles diet. Tadpoles exposed to predatory fish cues had smaller bodies, deeper tail fins, slower growth and development rates, and better rotational performance than tadpoles that were not exposed to predatory fish cues. Moreover, tadpoles appeared to differentiate between predatory fish diet and produced diet-specific responses in tail morphology and activity, although the latter effect was only marginally significant. Hatching, metamorphosis rates, and linear performance were not affected by the treatments. These results suggest that A. nebulosus can induce phenotypic changes in L. pipiens tadpoles, with some of these changes being diet specific.

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Pasanen, Mortensen Marianne. "Anthropogenic impact on predator guilds and ecosystem processes : Apex predator extinctions, land use and climate change." Doctoral thesis, Stockholms universitet, Zoologiska institutionen, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-100720.

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Humans affect ecosystems by changing species compositions, landscape and climate. This thesis aims to increase our understanding of anthropogenic effects on mesopredator abundance due to changes in apex predator status, landscape and climate. I show that in Eurasia the abundance of a mesopredator, the red fox (Vulpes vulpes), is limited top-down by the Eurasian lynx (Lynx lynx) and bottom-up by winter severity. However, where lynx has been eradicated, fox abundance is instead related to bottom-factors such as cropland (paper I, II). Fox abundance was highest when croplands constituted 25% of the landscape (paper II). I also project red fox abundance in Sweden over the past 200 years and in future scenarios in relation to lynx density, land use and climate change. The projected fox abundance was highest in 1920, when lynx was eradicated and the proportion of cropland was 22%. In 2010, when lynx had recolonised, the projected fox abundance was lower than in 1920, but higher than in 1830. Future scenarios indicated that lynx abundance must increase in respond to climate change to keep fox at the same density as today. The results suggest a mesopredator release when lynx was eradicated, boosted by land use and climate change, and that changes in bottom-up factors can modify the relative strength of top-down factors (paper IV). From 1846-1922, lynx, wolverine (Gulo gulo) and grey wolf (Canis lupus) declined in Scandinavia due to persecution; however I show that the change in wolverine abundance was positively related to the changes in lynx and wolf abundance. This indicates that wolverine is subsidized by carrions from lynx and wolf kills rather than limited top-down by them (paper III). This thesis illustrates how mesopredator abundance is determined by a combination of top-down and bottom-up processes, and how anthropogenic impacts not only can change the structures of predator guilds, but also may modify top-down processes through changes in bottom-up factors.

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: Submitted. Paper 4: Manuscript.

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Ddumba, Hassan. "Repulsive-attractive models for the impact of two predators on prey species varying in anti-predator response." Thesis, Nelson Mandela Metropolitan University, 2011. http://hdl.handle.net/10948/d1010995.

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This study considers the dynamical interaction of two predatory carnivores (Lions (Panthera leo) and Spotted Hyaenas (Crocuta crocuta)) and three of their common prey (Buffalo (Syncerus caffer), Warthog (Phacochoerus africanus) and Kudu (Tragelaphus strepsiceros)). The dependence on spatial structure of species’ interaction stimulated the author to formulate reaction-diffusion models to explain the dynamics of predator-prey relationships in ecology. These models were used to predict and explain the effect of threshold populations, predator additional food and prey refuge on the general species’ dynamics. Vital parameters that model additional food to predators, prey refuge and population thresholds were given due attention in the analyses. The stability of a predator-prey model for an ecosystem faced with a prey out-flux which is analogous to and modelled as an Allee effect was investigated. The results highlight the bounds for the conversion efficiency of prey biomass to predator biomass (fertility gain) for which stability of the three species ecosystem model can be attained. Global stability analysis results showed that the prey (warthog) population density should exceed the sum of its carrying capacity and threshold value minus its equilibrium value i.e., W >(Kw + $) −W . This result shows that the warthog’s equilibrium population density is bounded above by population thresholds, i.e., W < (Kw+$). Besides showing the occurrence under parameter space of the so-called paradox of enrichment, early indicators of chaos can also be deduced. In addition, numerical results revealed stable oscillatory behaviour and stable spirals of the species as predator fertility rate, mortality rate and prey threshold were varied. The stabilising effect of prey refuge due to variations in predator fertility and proportion of prey in the refuge was studied. Formulation and analysis of a robust mathematical model for two predators having an overlapping dietary niche were also done. The Beddington-DeAngelis functional and numerical responses which are relevant in addressing the Principle of Competitive Exclusion as species interact were incorporated in the model. The stabilizing effect of additional food in relation to the relative diffusivity D, and wave number k, was investigated. Stability, dissipativity, permanence, persistence and periodicity of the model were studied using the routine and limit cycle perturbation methods. The periodic solutions (b 1 and b 3), which influence the dispersal rate (') of the interacting species, have been shown to be controlled by the wave number. For stability, and in order to overcome predator natural mortality, the nutritional value of predator additional food has been shown to be of high quality that can enhance predator fertility gain. The threshold relationships between various ecosystem parameters and the carrying capacity of the game park for the prey species were also deduced to ensure ecosystem persistence. Besides revealing irregular periodic travelling wave behaviour due to predator interference, numerical results also show oscillatory temporal dynamics resulting from additional food supplements combined with high predation rates.

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Gourley, Stephen Alexander. "Nonlocal effects in predator prey systems." Thesis, University of Bath, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332378.

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Dall, Sasha Raoul Xola. "Information and the generalist predator problem." Thesis, University of Bristol, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296398.

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Chrobok, Viktor. "Harvesting in the Predator - Prey Model." Master's thesis, Vysoká škola ekonomická v Praze, 2009. http://www.nusl.cz/ntk/nusl-10510.

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The paper is focused on the Predator-Prey model modified in the case of harvesting one or both populations. Firstly there is given a short description of the basic model and the sensitivity analysis. The first essential modification is percentage harvesting. This model could be easily converted to the basic one using a substitution. The next modification is constant harvesting. Solving this system requires linearization, which was properly done and brought valuable results applicable even for the basic or the percentage harvesting model. The next chapter describes regulation models, which could be used especially in applying environmental policies. All reasonable regulation models are shown after distinguishing between discrete and continuous harvesting. The last chapter contains an algorithm for maximizing the profit of a harvester using econometrical modelling tools.

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28

Johannesen, Asa. "Predator-prey interactions in aquatic environments." Thesis, University of Leeds, 2013. http://etheses.whiterose.ac.uk/7556/.

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In the first half of this thesis, I have focused on predator ability to locate prey using olfaction and how prey aggregation and turbulence affect prey detection. In chapter 2 I investigate the ability of three spined sticklebacks to compensate for loss of visual cues by using olfaction and find that they can use olfactory cues but that these most likely help the fish detect prey rather than locate prey. In chapter 3 I explore the effect of prey aggregation as an anti-predator strategy when avoiding an olfactory predator and find that aggregated prey survive longer than do dispersed prey. In order to further investigate why this may be, I carried out an experiment using Gammarus pulex as the predator where I recorded search time as a function of prey group size. I found that similarly to detection distance, search time relates to the square root of the number of prey. Finally, I investigate the effect that turbulence in flowing water may have on prey group detection using three spined sticklebacks in a y-maze. I find that risk of detection increases with prey group size but that turbulence lowers this risk. This may mean that there are thresholds below which size prey groups can benefit from turbulence as a ‘sensory refuge’ thus avoiding predators. In the second part of my thesis I focus on the interactions between a cleaner fish and a parasite in an aquaculture setting focusing on whether said fish is useful as a cleaner in industry. I carry out experiments to investigate the use of lumpfish as salmon cleaners in terms of cleaning efficiency and behaviour. I find that while some lumpfish do clean salmon, the required circumstances are still unknown and that further work including selective breeding, personality and effects of tanks is necessary.

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Kotschwar, Mary Wynne. "Variation in predator communities and anti-predator behaviors of Milne-Edwards' sifakas (Propithecus edwardsi) in southeastern Madagascar." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/34266.

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To advance conservation in the increasingly fragmented landscape of Madagascar, we must examine the persistence and interactions of species in human-disturbed habitats. I investigated lemur-predator interactions in southeastern Madagascar through a comparison of predator communities and anti-predator behaviors of Milne-Edwards' sifakas (Propithecus edwardsi) in the continuous rainforest of Ranomafana National Park, and the forest fragments of Ialatsara Forest Station. I confirmed the presence of potential aerial predators at each site, but the sifakas' confirmed native mammalian predator, fossa (Cryptoprocta ferox), was absent from the fragmented site. Playbacks of predator vocalizations did not suggest that fragment-living sifakas have weakened anti-predator responses, but that their responses may be less specific than those of conspecifics in the continuous forest. I found that fragment-living sifakas displayed less downward vigilance and more frequently used low canopy heights; these behaviors may increase their vulnerability to recolonizing ground predators. I investigated local ecological knowledge (LEK) of carnivore ecology in communities 0–20 km from continuous forest to explore the potential for such recolonization. My findings from 182 interviews in 17 communities suggest that the fossa is especially sensitive to anthropogenic disturbance; it was only observed in communities ≤ 2.5 km from the continuous forest within the last five years. In contrast, the introduced small Indian civet (Viverricula indica) and wild cat (Felis silvestris) were distributed ubiquitously and displayed an affinity to human-dominated habitats. LEK surveys can provide information on the poorly understood responses of the Malagasy carnivores to the threats they face in a changing landscape.
Master of Science

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30

Waterworth, Rebeccah Anne. "Overcoming barriers to predation effect of alternative management practices on predator-herbivore dynamics in production nurseries /." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/2936.

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Thesis (M.S.) -- University of Maryland, College Park, 2005.
Thesis research directed by: Dept. of Entomology. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

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Lourenço, Rui Nascimento Fazenda. "Predatory interactions among vertebrate top predators superpredation and intraguild predation by large raptors." Doctoral thesis, Universidade de Évora, 2011. http://hdl.handle.net/10174/14789.

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Nesta tese estudaram-se as interacções predatórias entre vertebrados predadores de topo (predação intraguilda e superpredação), utilizando quatro aves de rapina de grande porte como modelos de superpredadores: Bufo-real, Açor, Águia-real, e Águia de Bonelli. A superpredação em aves de rapina é um fenómeno abrangente, que pode variar entre espécies, e mais frequente em paisagens mais humanizadas. Os meso-predadores não são recursos energeticamente relevantes para as aves de rapina, e o seu consumo está associado à diversificação da dieta resultante da diminuição das presas habituais. A eliminação de competidores e potenciais predadores são outros factores que podem aumentar a frequência da superpredação. O aumento da percentagem de meso-predadores na dieta está associado a menor sucesso reprodutor e maiores níveis de acumulação de mercúrio nas aves de rapina. O risco de predação pode levar um meso-predador (Coruja-do-mato) a diminuir a sua actividade vocal de modo a estar menos exposto ao predador intraguilda; ABSTRACT: This thesis analyses predatory interactions among vertebrate top predadores (intraguild predation and superpredation), using four large raptors as superpredator models: eagle owl, goshawk, golden eagle and Bonelli's eagle. Superpredation in raptors is a widespread phenomenon, that can vary between species, and that is more frequent in human-altered landscapes. Mesopredators are not energetically relevant resources for raptors, and their consumption is related to diet diversification as a result of the decline of staple prey. Competitor and predator removal are additional factors that can cause an increase in superpredation rates. The increase of mesopredators in the diet of raptors is associated to lower breeding success and higher levels of mercury contamination. Predation risk can drive a mesopredator (tawny owl) to reduce its vocal activity in order to be less exposed to its intraguild predator.

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Cox, Martin James. "Acoustic and ecological investigations into predator-prey interactions between Antarctic krill (Euphausia superba) and seal and bird predators." Thesis, St Andrews, 2008. http://hdl.handle.net/10023/579.

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Grason, Emily W. Miner Benjamin G. "Alien vs. predator : effects of a native predator on two invasive oyster drills and oysters in Washington State /." Online version, 2010. http://content.wwu.edu/cdm4/item_viewer.php?CISOROOT=/theses&CISOPTR=360&CISOBOX=1&REC=5.

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Kearns, Laura J. "Avian Responses to Predator Communities in Fragmented, Urbanizing Landscapes." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1338319171.

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Supriatna, Asep K. "Optimal harvesting theory for predator-prey metapopulations /." Title page, contents and abstract only, 1998. http://web4.library.adelaide.edu.au/theses/09PH/09phs959.pdf.

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Leone, Stacy E. "Predator induced plasticity in barnacle shell morphology /." Abstract Full Text (HTML) Full Text (PDF), 2008. http://eprints.ccsu.edu/archive/00000496/02/1952FT.htm.

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Thesis (M.A.) -- Central Connecticut State University, 2008.
Thesis advisor: Jeremiah Jarrett. "... in partial fulfillment of the requirements for the degree of Master of Arts in Biology." Includes bibliographical references (leaves 27-29). Also available via the World Wide Web.

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Van, Leeuwen Edwin. "Mathmatical Modelling of Predator-Multiple Prey Interactions." Thesis, Royal Holloway, University of London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.499202.

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Siekmann, Ivo. "Mathematical modelling of pathogen-prey-predator interactions." München Verl. Dr. Hut, 2009. http://d-nb.info/99326039X/04.

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39

Jiang, Yiting. "Anti-predator Behavior of Birds and Conservation." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS076/document.

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Prey s'appuie sur les décisions d'évasion lorsqu'il est confronté à des prédateurs pour maximiser les avantages de rester en place tout en réduisant les coûts de la prédation. Ce compromis de l'histoire de vie peut être reflété par la distance d'initiation de vol (FID), la distance à laquelle un individu prend son envol lorsqu'il est approché par un humain. J'ai abordé les facteurs potentiels expliquant la variation FID avec des données d'espèces d'oiseaux en Europe. La variabilité génétique était liée au risque de prédation FID; les espèces d'oiseaux menacées avaient généralement une FID plus longue que les espèces proches non menacées; le caractère distinctif de l'évolution (ED), un indicateur reflétant l'isolement phylogénétique des taxons, était positivement lié à la FID chez les oiseaux d'eau; La FID moyenne de différentes espèces d'oiseaux était positivement corrélée avec les niveaux spécifiques de MDA (malondialdéhyde qui est un indice de stress oxydatif) et UA (acide urique, qui est une mesure de la capacité antioxydante) et FID augmentée avec la taille du troupeau chez les espèces grégaires mais pas chez les espèces non grégaires. Ces résultats peuvent contribuer à la compréhension des causes et des conséquences des différences interspécifiques dans le comportement de fuite des prédateurs contre les prédateurs, et, plus important encore, ils peuvent fournir des moyens de résoudre les problèmes de conservation. Mots-clés : masse corporelle, taille du cerveau, taille effective de la population, modèle linéaire phylogénétique, stress oxydatif, comportement social
Prey rely on escape decisions when confronted with predators to maximize the benefits of staying put while reducing the costs of predation. This life history compromise can be reflected by flight initiation distance (FID), the distance at which an individual takes flight when approached by a human. I addressed potential factors explaining variation FID with data from bird species in Europe. Genetic variability was related to predation risk FID; threatened bird species generally had a longer FID than non-threatened closely related species; evolutionary distinctiveness (ED), an indicator reflecting the phylogenetic isolation of taxa, was positively related to FID in waterbirds; mean FID of different species of birds was positively correlated with species-specific levels of MDA (malondialdehyde which is an index of oxidative stress) and UA (uric acid, which is a metric of antioxidant capacity) and FID increased with flock size in gregarious species but not in non-gregarious species. These findings may contribute to the understanding of the causes and consequences of interspecific differences in anti-predator escape behavior of birds, and, more importantly they may provide means for resolving conservation problems. Key words: body mass, brain size, effective population size, phylogenetic linear model, oxidative stress, social behavior

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Maran, Audrey M. "Predator Contributions to Belowground Responses to Warming." Bowling Green State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1434114404.

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Penning, David A. "The Mechanisms of a Successful Intraguild Predator." Thesis, University of Louisiana at Lafayette, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10243639.

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The objective of this research was to quantify and better understand the mechanisms of performance in constricting snakes. Many non-venomous snakes use constriction to subdue and kill different types, sizes, and quantities of prey. Using eastern kingsnakes (Lampropeltis getula), I measured the effects of prey size and repeated feeding on constriction performance. I found that prey size alone did not affect constriction performance, but when kingsnakes encountered additional prey of medium and large sizes, they experienced significant reductions in the length of the body used and peak constriction pressure. In addition to feeding on a variety of different mammalian prey, kingsnakes (Lampropeltis spp.) are known to feed on other snakes, including other constrictors (Pantherophis ssp.). To begin addressing how this is possible, I studied the scaling of muscle cross-sectional area, pulling force as an indicator of escape performance, and constriction pressure as a measure of predation performance across the ontogeny of six species of snakes (three kingsnake and three ratsnake species). Muscle cross-sectional area and pulling force scaled similarly for all snakes, but all kingsnakes were able to exert significantly higher peak constriction pressures on their prey than ratsnakes. The ability to exert higher pressures suggests that kingsnakes may have differences in muscle anatomy and physiology that have gone untested. In another experiment, I described and quantified nine different muscles in speckled kingsnakes (L. holbrooki) and western ratsnakes (P. obsoletus) in order to better compare their anatomy. There were no significant differences in quantitative measures of musculature between these two species. Finally, I compared individual muscle performance between kingsnakes and ratsnakes by testing in vivo muscle force production and endurance. There was no difference between muscle force and endurance in our sample of kingsnakes and ratsnakes. The results from all chapters together indicate that kingsnakes are able to produce significantly higher constriction pressures because of their consistent coil posture (behavior) and not because of differences in their muscle anatomy or physiology. Integrated studies of behavior and its underlying mechanisms, such as in these chapters, are critical to making strong inferences about relationships in predator–prey interactions and their outcomes.

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Castro, Tatiane Marie Martins Gomes de [UNESP]. "Estudos taxonômicos e biológicos de Cunaxidae (Acari: Prostigmata) do Brasil." Universidade Estadual Paulista (UNESP), 2008. http://hdl.handle.net/11449/102306.

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Made available in DSpace on 2014-06-11T19:32:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-10-09Bitstream added on 2014-06-13T20:02:59Z : No. of bitstreams: 1 castro_tmmg_dr_jabo.pdf: 840130 bytes, checksum: 0cdb1be7253f471f413f5af3250d46f2 (MD5)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Os ácaros Cunaxidae são predadores de ácaros fitófagos, outros pequenos artrópodes e nematóides. O objetivo foi conhecer as espécies de Cunaxidae de ocorrência no solo e em plantas de dois ecossistemas naturais do Estado de São Paulo, Cerrado e Mata Atlântica e os aspectos biológicos de uma das espécies coletadas. Estudos sobre a diversidade desse grupo em ecossistemas naturais são importantes como uma informação a mais para justificar a conservação desses ecossistemas e também para uma possível utilização prática desses predadores como agentes de controle biológico de pragas em ecossistemas agrícolas. De um total de 561 espécimes de cunaxídeos, 42 espécies foram estudadas. Dentre essas espécies, 12 eram conhecidas e 30 eram espécies novas para a ciência. Portanto, cerca de 70% da diversidade consistia em espécies novas. Dentre as espécies conhecidas, apenas uma já havia sido constatada no Brasil. Por meio desse estudo, foi possível verificar uma grande diversidade de cunaxídeos em ecossistemas naturais do Estado de São Paulo. Dentre os táxons novos, 3 gêneros novos e 10 espécies novas foram descritos neste estudo. Uma das espécies novas, Cunaxatricha tarsospinosa, encontrada em plantas da vegetação natural (Mata Atlântica) e na cultura da seringueira do Estado do Mato Grosso do Sul e de São Paulo, teve seus aspectos biológicos avaliados quando alimentada com Tenuipalpus heveae.
The Cunaxidae mites are predators of phytophagous mites, other small arthropods and nematodes. The objective was to know the species of Cunaxidae occurring in the soil and on the plants of two natural ecosystems of the State of São Paulo, Cerrado and Atlantic Forest and the biological aspects of one of the species collected. Studies about the diversity of this group in natural ecosystems are important as additional inforrnation to justify the conservation of those ecosystems and for the possible practical use af these predatory mites as biological control agent of pests in agroecosystems. Df a total of 561 specimens of cunaxids, 42 species were studied. Among these species, 12 were known and 30 were new species to science. Therefore, about 70% of the diversity consisted in new species. Among the known species, just one was already known fram Brazil. Trough this study was possible to verify a high diversity of the cunaxid in the natural ecosystems of the State of São Paulo. Among the new taxa found, 3 new genera and 10 new species were described in this study. One of the new species, Cunaxatricha tarsospinosa, found on plants of the natural vegetation (Atlantic Forest) and on the rubber tree plantation of the State of Mato Grosso do Sul and São Paulo, has their biological aspects evaluated when fed with Tenuipalpus heveae.

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Hay, Alexandra Morag. "Foraging behaviour of the ruffe (Gymnocephalus cernuus) and predator avoidance by freshwater isopod Asellus aquaticus : implications for predator-prey interactions." Thesis, University of Glasgow, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312702.

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Becker, Matthew Smith. "Applying predator-prey theory to evaluate large mammal dynamics wolf predation in a newly-established multiple-prey system /." Thesis, Montana State University, 2008. http://etd.lib.montana.edu/etd/2008/becker/BeckerM1208.pdf.

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I studied wolf prey selection and kill rates during 1996-97 through 2006-07 winters in a newly established two-prey system in central Yellowstone National Park. Prey differed substantially in their vulnerability to wolf (Canis lupus) predation and wolves preyed primarily on elk (Cervus elaphus) but also used bison (Bison bison) to varying degrees within and among winters and packs. Winter severity, wolf abundance, distribution, and prey selection varied during the study, concurrent with variations in the demography, distribution, and behavior of elk and bison. A total of 759 wolf-killed ungulates were detected and prey selection by wolves was influenced by the absolute and relative abundance of prey types, the abundance of predators, and the duration of snow pack. Wolves strongly preferred elk calves relative to all other prey types, and elk calf abundance was inversely related to the occurrence of bison in wolf diets. Increasing wolf numbers also broadened prey selection from elk calves, and predation on bison and adult elk increased with increasing snow pack accumulation and duration, likely due to its long-term debilitating influence. Elk abundance and wolf pack size best explained variation in kill rates for elk while bison calf abundance and snow pack duration best explained kill rates of bison. The functional response of wolves for elk was best described by a Type II ratio-dependent model, indicating significant predator dependence. Prey-switching evaluations indicated increasing selection of bison with increasing bison:elk ratios, however no concurrent decrease in elk predation occurred. Increased bison predation is not solely dependent on relative abundance of the two prey species; therefore it is unlikely at this time that wolf prey-switching will stabilize the system.

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45

Nellis, Shelley. "EFFECTS OF ALTERNATIVE PREY AS A BUFFER TO PREDATION OF CHANNEL CATFISH (ICTALURUS PUNCTATUS) BY LARGEMOUTH BASS (MICROPTERUS SALMOIDES)." VCU Scholars Compass, 2010. http://scholarscompass.vcu.edu/etd/129.

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Channel catfish have pectoral spines that lock to defend against gape-limited predators such as largemouth bass. Previous work indicated that spines increase survival of channel catfish exposed to bass but did not determine whether bass avoid catfish if less dangerous species are available. We presented bass with channel catfish and two alternatives, bluegill and goldfish, and compared order of ingestion, ingestion time, percent of successful strikes, and time spent chasing each prey species. We also presented the three species in a jar study that standardized position in the water column as well as in a net-pen study. The order of ingestion was suggestive of a preference for goldfish, then bluegill and finally channel catfish. Handling time was greater for channel catfish, less for bluegill, and the least for goldfish. Fewer catfish were eaten when other prey were available. Bass appear to avoid channel catfish if alternative prey is available.

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Lindmark, Barbro. "Modulators of Vibrio cholerae predator interaction and virulence." Doctoral thesis, Umeå universitet, Molekylärbiologi (Medicinska fakulteten), 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-30211.

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Vibrio cholerae, the causal agent of cholera typically encodes two critical virulence factors: cholera toxin (CT), which is primarily responsible for the diarrhoeal purge, and toxin-co-regulated pilus (TCP), an essential colonisation factor. Nontoxigenic strains expressing TCP can efficiently acquire the CT gene through lysogenic conversion with CTXΦ, a filamentous phage that encodes CT and uses TCP as a receptor. V. cholerae is a Gram-negative bacterium and a natural inhabitant of estuarine and coastal waters throughout both temperate and tropical regions of the world. In the aquatic environment, V. cholerae encounters several environmental stresses, such as change in salinity, UV stress, nutrient limitation, temperature fluctuations, viral infections and protozoan predation. To fully understand the pathogenic and virulence potential of V. cholerae, knowledge is required of its interactions with, not only human, but also environmental factors. By using the nematode Caenorhabditis elegans as host model, we were able to identify a previously uncharacterised protein, the extracellular protease PrtV. PrtV was shown to be required for the killing of. elegans and also necessary for survival from grazing by the ciliate Tetrahymena pyriformis and the flagellate Cafeteria roenbergensis. The PrtV protein, which belongs to a M6 family of metallopeptidases was cloned and purified for further characterisations. The purified PrtV was cytotoxic against the human intestinal cell line HCT8. By using human blood plasma, fibrinogen, fibronectin and plasminogen were identified as candidate substrates for the PrtV protease. Outer membrane vesicles (OMVs) are released to the surroundings by most Gram-negative bacteria through “bulging and pinching” of the outer membrane. OMVs have been shown to contain many virulence factors important in pathogenesis. Therefore, we investigated the association of PrtV with OMVs. PrtV was not associated with OMVs from the wild type O1 strain. In contrast, in an LPS mutant lacking two sugar chains in the core oligosaccharide PrtV was found to be associated with the OMVs. The OMV-associated PrtV was shown to be proteolytically and cytotoxically active. V. cholerae strains are grouped into >200 serogroups. Only the O1 and O139 serogroups have been associated with pandemic cholera, a severe diarrhoeal disease. All other serogroups are collectively referred to as non-O1 non-O139 V. cholerae. Non-O1 non-O139 V. cholerae can cause gastroenteritis and extraintestinal infections, but unlike O1 and O139 strains of V. cholerae, little is known about the virulence gene content and their potential to become human pathogens. We analysed clinical and environmental non-O1 non-O139 isolates for their putative virulence traits. None of them carry the genes encoding CT or the TCP, but other putative virulence factors were present in these isolates. The incidence of serum resistance was found to vary considerably and was independent of encapsulation. Three strains were strongly serum-resistant, and these same strains could also kill C. elegans.

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Lagesson, Annelie. "Predator-induced morphological defences in a freshwater snail." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-44386.

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The ability of a certain genotype to express different phenotypes depending on variations in the environment is called phenotypic plasticity. Predator induced defences are among the most studied and wide spread examples of phenotypic plasticity. For example, in freshwaters, predators are constantly shaping communities with their presence and a plethora of defensive adaptations in prey have evolved.In this study, I have analyzed if the freshwater snail Radix balthica show any induced morphological defence when exposed to the molluscivoruos fishes, crusian carp (Carassius carassius) and tench (Tinca tinca). Two treatments were used; without predator and with a non-lethal predator (fish cues), to examine if the snails exposed to predators changed their shells in size, thickness and shape. The study contained snails from both northern Sweden (Umeå) and from southern Sweden (Lund).The experiment conducted on the northern snails of R. balthica did not confirm my hypothesis that snails threatened by a predator (fish cues) express inducible defences. However, there were tendencies pointing in that direction. In contrast, the R. balthica snails from southern Sweden, exposed to fish cues from tench, showed a strong response. Shells were thicker and showed a more rounded shape, i.e. a wider shell and lower apex in the presence of fish compared to in the absence of fish. The rounder shells are more resistant to crushing by molluscivorous fish, due to the fact that the crushing force is more evenly spread over the shell. Thickness and size of the shell also influences the crushing resistance. Shell crushing fish obviously have a strong effect on gastropod communities and are therefore likely to drive the evolution of induced morphological defence in their prey.

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Blixt, Torbjörn. "The behavioural response of mice to predator odours." Thesis, Linköpings universitet, Biologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-79068.

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The ability to detect and react to a predator odour is crucial for prey species. In the present study 10 mice (Mus musculus) were used to test the behavioural response of mice towards two predator odours (3-methyl-1-butanethiol and 3-mercapto-3-methyl-butan-1-ol) and one fruity odour (n-pentyl acetate). All three odours were tested against a near odourless blank stimulus (diethyl phthalate). The animals were individually placed in a test chamber of two equally sized compartments divided by a vertical Plexiglas wall with a semicircular opening. Their proximity to the odours, placed beneath the floor in petri dishes in each compartment, was measured continuously with stop watches. The mice spent less time in proximity to 3-methyl-1-butanethiol and n-pentyl acetate compared to diethyl phthalate (P<0,05). The mice did not prefer any specific compartment in the test with 3-mercapto-3-methyl-butan-1-ol compared to diethyl phthalate (P>0,05). The avoidance of 3-methyl-1-butanethiol and n-pentyl acetate can be explained either by neophobia, or in the case of 3-methyl-1-butanethiol that it contains sulphur. The lack of behavioural response towards 3-mercapto-3-methyl-butan-1-ol may be due to its loss of intensity over time. From this study it is not certain if mice have an innate fear of predator odours.

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Merchant, Sandra M. "Spatiotemporal patterns in mathematical models for predator invasions." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/17988.

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Much attention has been given to oscillatory reaction-diffusion predator-prey systems recently because, in the wake of predator invasions, they can exhibit complex spatiotemporal patterns, notably wave trains and associated irregular spatiotemporal oscillations, thought to occur in natural systems. This thesis considers the generation and stability of spatiotemporal patterns behind invasion in these models and an extension that includes non-local intraspecific prey competition. In the first part, we study the mechanism by which a single member is selected from a continuous family of wave train solutions behind the invasion. This was first studied by Sherratt (1998), where the author develops a selection criterion that is valid near a supercritical Hopf bifurcation in the kinetics and when the predator and prey diffuse at equal rates. We formulate a ``pacemaker" selection criterion that generalizes the criterion of Sherratt (1998), but does not depend on these assumptions. We test this pacemaker criterion on three sample systems and show that it provides a more accurate approximation and can apply to unequal diffusion coefficients. In the second part of the thesis, we study the effect of including non-local intraspecific prey competition in these systems. We first study the qualitative effect of non-local competition on the spatiotemporal patterns behind predator invasions in these models, and in a related caricature system. We find that non-local prey competition increases the parameter range for spatiotemporal pattern formation behind invasion, and that this effect is greater for lower kurtosis competition kernels. We also find that sufficiently non-local competition allows the formation of stationary spatially periodic patterns behind invasion. Second, we revisit the selection and stability of wave train solutions. We modify the selection criterion from the first part, also applying it to the non-local system, and study how the properties of selected wave trains vary with the standard deviation of the non-local prey competition kernel. We find that the wavelength of selected wave trains decreases with the standard deviation of the non-local kernel and also that unstable wave trains are selected for a larger parameter range, suggesting that spatiotemporal chaos may be more common in highly non-local systems.

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Östergård, Hannah. "Plant-seed predator interactions – ecological and evolutionary aspects." Doctoral thesis, Stockholm University, Department of Botany, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-7537.

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Plant-animal interactions are affected by both abundance and distribution of interacting species and the community context in which they occur. However, the relative importance of these factors is poorly known. I examined the effects of predator host range, environmental factors, host plant populations, plant traits and fruit abortion on the intensity of pre-dispersal seed predation in 46 host populations of the perennial herb Lathyrus vernus. I recorded damage by beetle pre-dispersal seed predators, mainly Apion opeticum and Bruchus atomarius with different host ranges on L. vernus as well as on two additional host plants. Local seed predator population size was mainly influenced by plant population size, current seed production and beetle population size in the previous year, but was not strongly affected by connectivity. The monophagous seed predator was less abundant and had lower densities than the oligophagous. Both predator species had a strong ability to track fluctuations in seed production; intensity of predation increased with relative increases in seed production. Oligophagous predation on L. vernus increased with the abundance of alternative hosts, but presence of L. vernus did not affect predation on alternative hosts. Abundances and trait preferences differed among three co-occurring seed predators, but were also associated with the abundance of the other species. Overall, seed predation influenced selection on flower number. I found clear indications of seed predator offence but no obvious plant defence. The pattern of fruit abortion was associated with reduced plant fitness since the seed predator had an advanced ability to locate fruits with high probability of retention. Taken together, different factors influencing abundance of the seed predator species, different preferences, and context dependent trait selection are likely to result in complex spatio-temporal variation in overall seed losses and trait selection in the common host plant.

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Dissertations / Theses on the topic 'Predator of'

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