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1
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 <italic> P. melanarius</italic> 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 <italic> P. melanarius.</italic> The mucus defence of live slugs (<italic>Deroceras reticulatum)</italic> deterred attacks by beetles, but feeding on dead <italic> D. reticulatum</italic> emphasized a preference for this prey type by <italic> P. melanarius.</italic> (2) The survival rate of <italic>D. reticulatum</italic> bitten by <italic>P. melanarius</italic> was not different to that of non-attacked control slugs. Attacking bites by <italic>P. melanarius,</italic> visited upon live slugs, did not yield slug DNA-positive results during molecular analysis of beetle foregut contents. (3) <italic>Pterostichus melanarius</italic> was not able to detect by olfaction the presence of live or 12 h-decayed dead <italic> D. reticulatum.</italic> (4) The feeding history of <italic>P. melanarius </italic> 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 <italic>P. melanarius </italic> 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 <italic>P. melanarius</italic>.
2
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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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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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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Latif, Quresh S. "How predation risk shapes avian nest site selection and processes underlying nest predation patterns." Diss., [Riverside, Calif.] : University of California, Riverside, 2009. http://proquest.umi.com/pqdweb?index=0&did=1957706911&SrchMode=2&sid=4&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1268765320&clientId=48051.
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Thesis (Ph. D.)--University of California, Riverside, 2009.<br>Includes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed March 16, 2010). Includes bibliographical references. Also issued in print.
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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.
7
Songjang, Khemika. "Peptides to inhibit crop predation." Thesis, University of Reading, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428155.
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Low, Petah Alexandra. "The ecology and behaviour of eucalypt-feeding caterpillars in response to predation risk." Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/15898.
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It was traditionally assumed that predator effects were lethally transmitted, however there is now increasing evidence of the importance of their non-consumptive effects. I outline a conceptual framework that integrates both the consumptive and non-consumptive pathways for predator effects on insect herbivores. Using this framework, I aimed to improve our understanding of predator effects on insect herbivores in the Eucalyptus system. First I investigated how the plant traits- leaf age and location- affect predation risk, and also whether this risk varied with type of predator. I found no evidence for a difference in risk. I then manipulated head capsule stacks on Uraba lugens larvae to investigate their putative defensive function. I found that the retention of moulted head capsules provides some protection against natural enemies by serving as a false target as well as a weapon to fend off attackers. Next I investigated the behavioural responses of caterpillars to variation in a direct physical cue of predation risk, non-lethal predator attacks varying in location and frequency. I found that the type and extent of response varied according to the location and frequency of attack, suggesting that these caterpillars have the capacity to distinguish different levels of risk. I also investigated how both the behaviour and physiology of caterpillars are influenced by multiple cues of predation risk. I found that the direct physical cue invoked both short term behavioural responses and long-term physiological ones, while the indirect chemical cue invoked only short-term physiological responses. Finally my thesis also addressed a number of methodological aims regarding the use of model prey. I confirmed the validity of models as surrogates for real prey in a field setting. I also collated a comprehensive reference collection of attack marks and established guidelines for identifying predators responsible for attacks on models.
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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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Tomaszewska, Ewa. "Testing for predation in airline markets." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq23078.pdf.
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Speed, Michael Patrick. "Mimicry and the psychology of predation." Thesis, University of Leeds, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278364.
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Wright, David Andrew. "Protozoan predation of bacteria in soil." Thesis, University of Aberdeen, 1994. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU068158.
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Survival of P. fluorescens 10586s FAC510 was studied in liquid culture and soil microcosms in the presence of the ciliate C. steinii and the flagellate Cercomonas sp. Both protozoa caused a reduction in bacterial viable cell concentration, however the ciliate caused a greater decrease in abundance. Starvation of the bacterial prey caused a reduction in grazing rates of both the ciliate and flagellate, indicating the lower nutrional quality of starved as opposed to non-starved cells. Manipulation of the physiological state of prey cells, by starvation, had much the same effect as observed when bacterial prey resources are reduced. Luminescence provided a valuable marker for monitoring P. fluorescens 10586s FAC510 in liquid culture and soil, since detection by luminometry provided a sensitive, rapid, and non-extractive technique for measurement of microbial activity. In the presence of C. steinii, bacterial activity increased, whilst predation by Cercomonas sp. caused a reduction. The different responses of the bacterial inoculum may reflect the divergent balance between bacterial turnover, leading to nutrient regeneration, and grazing strategies, which are selective of the two protozoa. The distribution of bacterial cells in the soil pore network was manipulated by adjustment of the antecedant matric potential prior to inoculation. The ability to predominantly place bacterial and protozan cells in specific pore size classes was confirmed by partial chloroform fumigation and resin impregnated sections of soil.
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Sundell, Janne. "Vole population dynamics : experiments on predation." Helsinki : University of Helsinki, 2002. http://ethesis.helsinki.fi/julkaisut/mat/ekolo/vk/sundell/.
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Johnson, Kevin Brett. "Predation on planktonic marine invertebrate larvae." Thesis, Thesis (Ph. D.)--University of Oregon, 1998, 1998. http://hdl.handle.net/1794/10086.
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Dryden, Robert Cumming. "Predation of cyanobacteria by Acanthamoeba spp." Thesis, University of Bath, 1987. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376341.
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Molin, Johan. "Predation på evertebrater under tidig vår i sjön Tåkern." Thesis, Linköpings universitet, Biologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-79044.
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Benthic invertebrates play important roles as feeding resources for many organisms in different food webs. Shifts in predation of these organisms can generate cascading effects and potentially lead to the disappearance of one or more species from a site. Cascading effects can bring impacts to organisms who aren’t even directly involved, why studies in this field are important for understanding sudden changes in ecosystems. I examined the predation from fish and waterfowl on benthic invertebrates in the shallow and eutrophic Lake Tåkern in the plains of Östergötland County, southern Sweden. The study was experimental and used exclosures (three types, eight replicates) in the shape of 130-liter cages to examine the composition of invertebrates. It was conducted during early spring, a relatively unexamined period for this kind of study. I found no significant differences in the control treatment compared to any of the other treatments regarding biodiversity. The invertebrate fauna was dominated by a small number of species, with a relatively patchy spread throughout the sediment area. Furthermore, the results indicate that the fish hadn’t had the time to properly activate their predatory habits due to prolonged winter temperatures. The waterfowl were considered too absent during the test period to affect the invertebrate community. Future studies in this area are recommended to work with a greater sampling area, to reduce the influence of extreme values.
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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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Lindberg, Benjamin. "Predation as a driver of reproductive isolation : Differences in predation risk between whitefish (Coregonus lavaretus) spawning habitats." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-184959.
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The origin and maintenance of much of natural biodiversity can likely be explained by theecological speciation theory. Ecological speciation is defined as the process whenreproductive isolation arises through divergent selection caused by ecological factors, such asbiotic interactions and abiotic conditions. Many populations of European whitefish(Coregonus lavaretus) are currently going through sympatric speciation from a single littoralecotype to two or more ecologically separate ecotypes. It has been hypothesized that northernpike (Esox lucius) is promoting speciation in whitefish by exposing it to a trade-off betweenpredation risk and resource availability causing an initial divergence in size eventuallyleading to two or more ecologically and genetically distinct ecotypes. After initial divergencesmall whitefish ecotypes often abandon ancestral spawning sites to spawn in streams or deepwater suggesting that the ecotypes are at least partially reproductively isolated. The driver ofthis reproductive isolation could be predation risk as pike mainly forage in the littoral. If thisis true, we would expect to find significantly higher predation risk for small whitefish at thelittoral spawning sites than on alternative spawning sites. To test this idea, hooks baited withsmall whitefish was placed at different spawning sites during the fall spawning season andchecked every 12 hour for 36 hours. Relative predation risk for small whitefish wassignificantly higher at the ancestral littoral spawning sites than at stream spawning sites. Inaddition, there was a significant decrease in predation risk later in the spawning season. Thisindicates that predation is promoting reproductive isolation in European whitefish byselecting against small individuals spawning at littoral spawning sites, but potentially also byselecting for delaying spawning in small individuals in the littoral. To fully understand thespeciation process in this system more studies must be done considering the complexity ofthe speciation process. Because of the lack of studies investigating predation as a cause ofbehavioral changes, that in turn promotes reproductive isolation, future studies should putmore emphasis on predation as a possible driver of reproductive isolation.
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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.<br>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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Palmer, Brian C. "Predation on Domestic Sheep on Summer Range Lands in Southwestern Utah." DigitalCommons@USU, 2009. https://digitalcommons.usu.edu/etd/362.
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Much of the decline of the U.S. sheep industry has been attributed to losses caused by predators. Most predatory losses are inflicted on lambs rather than ewes. Losses have historically ranged from 4-8% of lamb crops, inflicting significant financial loss on ranchers. However, most research providing data on sheep predation is over 20 years old. Changes in the sheep industry as well as predation rates may make previous loss rates inapplicable to current conditions. Coyotes (Canis latrans) are the primary predator of concern when it comes to sheep losses, but increasingly, cougars (Felis concolor) and black bears (Ursus americanus) are reported to be responsible for an increased proportion of lamb losses. I replicated a sheep depredation study conducted during the early 1970s in southwestern Utah and compared the results of the two studies to reassess losses and the predator species responsible for those losses.
Total lamb losses to all causes in my study were comparable to losses reported in the 1970s as well as categories of verified and estimated predator losses. There was a significant variation in lamb losses between the 2 years of my study due to an increase in predator kills on sheep. Cougar and bear depredations occurred at significantly higher rates during my study than during the 1970s but did not produce an additive effect to overall predator losses.
Most lambs killed by predators were located on or near pasture bed grounds as reported by other studies, but a large number were found >500 m from bed grounds. Rough terrain and scavenging by California condors (Gymnogyps californianus) made location of missing sheep difficult. The ability of cougars and bears to remove sheep carcasses from kill sites made the finding of sheep carcasses more difficult and caused an underreporting of sheep killed by these predators. I found that the loss of sheep to predation continues to be a problem for the sheep industry and its magnitude was unchanged from historic predation levels.
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Ryan, Daniel P. "Fitness Dependent Dispersal in Intraguild Predation Communities." Scholarly Repository, 2011. http://scholarlyrepository.miami.edu/oa_dissertations/608.
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A model of a three species intraguild predation community is proposed. The model is realized as a system of cross-diffusion equations which allow the intraguild prey species to adjust its motility based on local resource and intraguild predator densities. Solutions to the cross-diffusion system are shown to exist globally in time and the existence of a global attractor is proved. Abstract permanence theory is used to study conditions for coexistence in the ecological community. The case where the intraguild prey disperses randomly is compared to the case where the intraguild prey disperses conditionally on local ecological fitness and it is shown that the ability of the intraguild prey to persist in the ecological community is enhanced if the intraguild prey utilizes a movement strategy of avoiding areas with negative fitness. A finite element scheme is used to numerically simulate solutions to the system and confirm the analytical results.
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Mitchell, Dustin L. "Cougar Predation Behavior in North-Central Utah." DigitalCommons@USU, 2013. http://digitalcommons.usu.edu/etd/1539.
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Cougar (Puma concolor) predation has been identified as being one of several factors contributing to the decline of mule deer (Odocoileus hemionus) throughout the Western United States. In order to better understand how these elusive felines utilize their surroundings and prey, I examined and analyzed cougar predation behavior in North-Central Utah, using global positioning systems (GPS) data from 2002-2010. Twenty-three cougars were fitted with GPS collars and monitored for prey caching behavior. In total 775 potential cache sites were visited and 546 prey remains found. Mule deer comprised the majority of prey at cougar cache sites, but 11 other species were also found. Collectively, adult female mule deer were killed more than any other demographic class. Proportionally there was no difference in the sex or age class of deer killed by cougars in three different population segments, but seasonal differences were found in the number of kills made between cougar groups. Female cougars with kittens had a higher predation rate than males or solitary females, and seasonally more kills were made in the winter vs. summer. Cougars spent an average of 3.3 days on deer kills, and 6.2 days on elk kills. Habitat analyses suggested that cougars preferentially used Gambel oak (Quercus gambelii) over other land cover types when caching prey, as well as selected unburned over burned areas for caching and foraging on prey. These results suggest that cougars utilize dense stands of vegetation cover when stalking and concealing their prey. Wildlife managers may want to consider the use of prescribed burns in areas of high cougar predation on mule deer. This habitat manipulation tool could simultaneously help mule deer populations by reducing the percent of stalking cover afforded to cougars when attempting to kill prey, along with increasing nutrient levels of newly burned foliage and allow for an increased diversity in forb and shrub species available to mule deer.
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Okuyama, Toshinori. "Maintenance of intraguild predation in jumping spiders." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013605.
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Al, rubaiee Zaid. "Microorganisms, flight, reproduction, and predation in birds." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS097/document.
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Les coûts de remise en forme que les macro et micro parasites imposent aux hôtes peuvent s'expliquer par trois facteurs principaux : (1) Les hôtes utilisent des réponses immunitaires contre les parasites pour prévenir ou contrôler l'infection. Les réponses immunitaires nécessitent de l'énergie et des nutriments pour produire et / ou activer les cellules immunitaires et les immunoglobulines, ce qui est coûteux, provoquant des compromis avec d'autres processus physiologiques comme la croissance ou la reproduction. (2) Le taux métabolique de l'hôte peut être augmenté parce que les dommages aux tissus et la réparation ultérieure de l'infection causée par le parasite peuvent être coûteux. (3) Le taux métabolique des hôtes peut augmenter et donc augmenter également leurs besoins en ressources. La compétition entre macro-parasites et hôtes peut priver les ressources de l'hôte. Les coûts de remise en forme que les macro et micro parasites imposent aux hôtes peuvent s'expliquer par trois facteurs principaux : (1) Les hôtes utilisent des réponses immunitaires contre les parasites pour prévenir ou contrôler l'infection. Les réponses immunitaires nécessitent de l'énergie et des nutriments pour produire et / ou activer les cellules immunitaires et les immunoglobulines, ce qui est coûteux, provoquant des compromis avec d'autres processus physiologiques comme la croissance ou la reproduction. (2) Le taux métabolique de l'hôte peut être augmenté parce que les dommages aux tissus et la réparation ultérieure de l'infection causée par le parasite peuvent être coûteux. (3) Le taux métabolique des hôtes peut augmenter et donc augmenter également leurs besoins en ressources. La compétition entre macro-parasites et hôtes peut priver les ressources de l'hôte<br>The fitness costs that macro- and micro-parasites impose on hosts can be explained by three main factors: (1) Hosts use immune responses against parasites to prevent or control infection. Immune responses require energy and nutrients to produce and/or activate immune cells and immunoglobulins, and that is costly, causing trade-offs against other physiological processes like growth or reproduction. (2) The host’s metabolic rate can be increased because tissue damage and subsequent repair from the infection caused by parasite may be costly. (3) The metabolic rate of hosts may increase and hence also increase their resource requirements. Competition between macroparasites and hosts may deprive resources of host. Birds are hosts for many symbionts, some of them parasitic, that could decrease the fitness of their hosts. There is a huge diversity in potential parasites carried in a bird’s plumage and some can cause infection. Nest lining feathers are chosen and transported by adult birds including barn swallows Hirundo rustica to their nests, implying that any heterogeneity in abundance and diversity of microorganisms on feathers in nests must arise from feather preferences. we found that the effects of microorganisms on the behavior of birds may be a combination of positive and negative effects. There may be positive effects of antimicrobial activity on birds through the process of bacterial interference, consisting of certain bacteria impeding the establishment of competing bacterial strains by producing antibiotic substances. Meanwhile, the negative effects may imply that pathogenic or/and feather-degrading microorganisms may reduce fitness components of their hosts. These effects of microorganisms and hence the microbiome can be affected by the behavior of bird hosts
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Peterson, Alison. "EFFECTS OF SIZE AND EXPOSURE TO PREDATION THREAT ON MATING BEHAVIOR AND PREDATION RESPONSE IN MALE WESTERN MOSQUITOFISH (GAMBUSIA AFFINIS)." MSSTATE, 2004. http://sun.library.msstate.edu/ETD-db/theses/available/etd-04022004-205940/.
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Trade offs between mating and predator avoidance advantages were studied in the western mosquitofish (Gambusia affinis: Poeciliidae). When tested with green sunfish (Lepomis cyanellus) predators, larger male G. affinis were found to have a higher number of escapes compared to smaller males. Smaller males were captured more often than larger males in groups of six and in both complex and simple habitat types. Large males, on average, were found to attempt more matings and spend a larger proportion of time near the female than smaller males. When trials with predators were compared to trials without predators, large males decreased mating attempts and time spent near the female although, small males increased time spent near females. Size of the predator did not affect these behaviors. Fry were reared under varying levels of predator exposure (visual, olfactory, both, or neither) and predation response was measured for each group at maturity. Results were not significant and were confounded by G. affinis size.
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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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Marshall, Jason Paul. "Analysis of predation data from moose-wolf systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq21189.pdf.
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Larivière, Serge Jacques. "Habitat fragmentation, striped skunks, and waterfowl nest predation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ27417.pdf.
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Delaire, Lari. "Predation, parasitism and colour in natural guppy populations." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103592.
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Many studies of evolution adopt a unifactorial approach, where a single causal force appearing to account for a majority of the phenotypic variation becomes the focal point of investigation. However, it seems certain that no single force acts to the complete exclusion of other forces, and so multi-factorial studies can make a crucial contribution to our understanding of the evolution of phenotypic variation. In the Trinidadian guppy system, natural selection acting via predation has long been recognized as playing an important role in shaping trait variation. However, other environmental factors also likely contribute, and my thesis explores the potential role of one of them: parasitism. I specifically focus on Gyrodactylus, a monogenean ectoparasite that has important effects on many fish species and coexists with guppies in the wild. I evaluate the extent to which parasitism varies among guppy populations, particularly in relation to predation. I then ask whether parasitism influences phenotypic variation in guppy traits. This work was executed through a large-scale survey in northern Trinidad, where 26 guppy populations of known predation level (high or low) were surveyed across 10 different rivers. Individual guppies were scanned for Gyrodactylus and then photographed for image analyses aimed at quantifying body size and aspects of male colour. I found that among-population variation in parasitism levels was consistent between two dry seasons, and that high-predation localities tend to have higher levels of parasitism than do low-predation localities. However, I found few effects of parasitism on guppy traits and no major modifying influence of parasitism on inferences about the role of predation. Although more work certainly needs to be done with respect to parasitism, our results suggest it might be more profitable to concentrate on other potential causal factors that shape guppy trait variation.<br>De nombreuses études sur l'évolution adoptent une approche uni-factorielle qui se concentrent sur une seule force pouvant expliquer la plupart de la variation phénotypique observée. Cependant, il est évident qu'aucune force n'exerce son effet de façon isolée. C'est pourquoi les études multi-factorielles apportent une contribution cruciale à notre compréhension de l'évolution de la variation phénotypique. Dans le système d'étude des guppies de Trinité, la sélection naturelle imposée par les prédateurs a depuis longtemps été considérée comme un facteur important dans l'élaboration de la variation au niveau des traits. Cependant, d'autres facteurs environnementaux contribuent également à cette élaboration, notamment le parasitisme. Je me penche sur le rôle potentiel que peuvent avoir les parasites du genre Gyrodactylus sur les traits des guppies. Ces ectoparasites monogènes exercent de nombreux effets sur plusieurs espèces de poissons et coexistent avec les guppies dans leur environnement naturel. J'évalue le niveau de variation du parasitisme entre les populations de guppies, et plus spécifiquement en relation avec la prédation. J'explore par la suite l'influence potentielle du parasitisme sur la variation phénotypique des traits des guppies. Pour ce faire, une étude de grande échelle a été effectuée sur 10 rivières dans le nord de Trinité, dans laquelle 26 populations sujettes à des niveaux de prédation connus (élevé ou bas) ont été inventoriées. L'état d'infection par les Gyrodactylus a été répertorié pour chaque guppy, puis les poissons ont été photographiés pour analyser les images dans le but de quantifier la taille corporelle ainsi que de nombreux aspects de la coloration chez les mâles. J'ai trouvé que les niveaux de parasitisme entre les populations étaient consistants entre les deux saisons sèches recensées, et qu'il y a une tendance pour les sites de haute prédation à avoir des niveaux de parasitisme plus élevés que les sites de basse prédation. Cependant, j'ai trouvé que la parasitisme avait peu d'effets sur les traits des guppies et aucune influence majeure n'a été trouvée sur les inférences concernant la prédation. Bien qu'il reste encore beaucoup de travail à faire en ce qui a trait au parasitisme, nos résultats suggèrent qu'il pourrait être plus profitable de se concentrer sur d'autres facteurs potentiels pouvant expliquer la variation de traits chez les guppies.
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Marples, Nicola. "The influence of predation on ladybird colour patterns." Thesis, Cardiff University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321365.
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Jumeau, Philippe J. A. M. "Arthropod predation in a simple Antarctic terrestrial community." Thesis, University of York, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277219.
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Davey, Jeffrey Stewart. "Intraguild predation among generalist predators in winter wheat." Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/55042/.
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Modern annual arable crops are susceptible to outbreaks of pests due mainly to the uniform habitats that agricultural fields represent. Cereals are particularly prone to infestations of aphids, which may damage the crop directly through herbivory, or indirectly by acting as vectors of disease. These insects, however, have a large range of invertebrate natural enemies, which under certain circumstances, can maintain infestations below economically damaging levels. Greater habitat complexity at landscape and farm scale usually leads to more diverse assemblages of natural enemies at the field scale, but such diversity less often translates to a higher risk for pests. When higher natural enemy diversity is associated with lower levels of pest control, intraguild predation (IGP) is often cited as one of the primary antagonsitic mechanisms. IGP occurs where predators not only compete for the same resource, but also partake in a trophic interaction with one another. Controlled experiments suggest that the niche proximity of predators relative to each other and their shared prey may help predict the outcome of multiple- predator interactions. The primary aim of this thesis was to assess levels of IGP amongst generalist invertebrate predators and to elucidate their spatial patterns, in fields of winter wheat (<italic>Triticum aestivum</italic>), an important cereal crop in North-West Europe. The chief objective was to establish the regulatory abilities of these predators in the control of aphids. Post-mortem gut content analysis using PCR was used to establish the intensity of IGP by two polyphagous predators, the carabid beetles <italic>Pterostichus melanrius</italic> and <italic>P. madidus</italic>, on a number of insectivorous linyphiid spiders and their shared aphid prey. Each of the spiders tested was found to suffer IGP. Predation rates were adjusted using data from controlled feeding trials and resampled using Monte Carlo models to test the hypothesis that predation was density-dependent. In one experiment, the web-occupying linyphiid <italic>Tenuiphantes tenuis</italic> was consumed by up to a third of <italic>P. melanarius</italic>. Predation rates by carabids on the linyphiid <italic> Bathyphantes gracilis</italic> were consistently lower than expected. <italic> B. gracilis</italic> also relies principally on its web to capture prey, but builds these webs significantly higher in the wheat stem than <italic>T. tenuis </italic>. Preferences for intraguild prey species more likely to hunt aphids on the ground, the tetragnathid spider <italic>Pachygnatha degeeri</italic>, and the linyphiids Erigone spp. (<italic>E. atra</italic> and <italic>E. dentipalpis </italic>), were less consistent than those species more dependent on their webs to hunt aphids and other prey. While many factors may contribute to the outcomes of multi-predator interactions, these findings broadly supported the hypothesis that niche proximity of intraguild predators is positively related to levels of disruption due to intraguild interactions.
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Tyler, Carrie Leigh. "Investigating Predation in the Fossil Record: Modern Analogs." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/77194.
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Predation is considered a powerful ecological force influencing community structure, diversity, and abundance. Paleoecology offers a unique perspective, allowing us to examine ecological processes such as predation over evolutionary timescales. The three studies summarized below include two case studies testing the role of predation in evolution and one method-oriented project, which explores new tools with which to examine predator-prey interactions in the fossil record. Considering the importance of community interactions in the current global biodiversity crisis, understanding ecological and evolutionary dimensions of predation is critical to conservation biology and ecology, as predators are thought to play a vital role in maintaining ecosystem health and biodiversity.
Predation has been dismissed as a causal mechanism for some major prey groups. For example, the evolutionary decline and cryptic or antitropical distribution of brachiopods is often explained as due to the potentially low energetic value and suspected non-palatability or toxicity of brachiopod tissues. Here we demonstrate that multiple invertebrate marine predators (crustaceans, echinoderms, and gastropods) are willing and able to consume brachiopods, and that predation pressure on the living brachiopod population may be consequential. Examination of the fossil record is consistent with this interpretation: evidence for drilling and repair of brachiopod shells is found throughout the fossil record in multiple orders. This suggests that although brachiopods may be unwanted prey in the presence of energetically more desirable targets, they do appear to be edible and are subject to intense predator-prey interactions.
Limpets are important prey for some crab species, yet little is known about the role of durophagy in the evolution of the limpet shell. Feeding trials using three common species of Pacific Northwest limpets (Lottia digitalis, L. pelta and Tectura scutum) were conducted to assess how different shell morphologies affect mortality and handling time. We predicted that large size, shell ornament, and low-spires would result in either increased survivorship, and/or longer handling times. Contrary to our expectation that ridges resist predation, individuals with smooth morphologies experienced significantly lower mortality, as did those with low-spires. As species possessing high-spires and ridges typically occur high in the intertidal where predation risk due to crabs is relatively low, these morphologies are likely adaptions to physical factors such as thermal stress.
One of the major caveats of using gastropod drill holes to assess predator-prey interactions in both the modern and the ancient is the correct identification of drill holes of predatory origin. By examining known predatory drill holes using environmental scanning electron microscopy, we aim to refine the development of a novel technique for augmenting their identification, and to explore the relationship between predator body size, predatory radula dentition, and radular microrasping marks observed on the shells of prey organisms. Electron micrographs were used to measure the spacing of microrasping marks produced by the radula, and the intercusp spacing of the radula dentition. A relationship between predator body size and microrasping marks makes it possible to infer predator size from these microtraces in both modern and fossil specimens, augmenting our ability to examine predator-prey interactions throughout the history of this important ecological interaction.
Proxies for predation intensity such as predation traces or antipredatory morphologies provide an invaluable method to examine predation in both modern communities, and the fossil record. Our understanding of the importance of predation in regulating biodiversity and in evolution will continue to grow with the development of new methodologies, and a comprehensive understanding of predatory defenses.<br>Ph. D.
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Morling, Frances. "Cape Town's cats: reassessing predation through kitty-cams." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/9099.
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Includes bibliographical references.<br>Domestic cats (Felis catus) are abundant generalist predators that exploit a wide range of prey within and adjacent to the urban matrix. Cats are known to have contributed to the extinction and endangerment (mostly on islands) of a number of indigenous species, including birds, small mammals, reptiles and amphibians. Most research on this important topic has been carried out in the developed world, predominantly in Australia, New Zealand, the U.K., the U.S. and Canada with only four studies carried out in Africa. Of these, two studies in Cape Town suggest that domestic cats have a big impact on wildlife but these studies may have underestimated predation because they failed to account for the proportion of prey not returned to participants’ homes. In this study I used kitty-cams in an attempt to provide a prey correction factor for urban cats in Cape Town, South Africa. I investigated hunting of wildlife by free-ranging domestic cats in Newlands, a suburb of Cape Town, South Africa over 5 weeks in 2013. I monitored 13 cats (6 deep-urban and 7 urban-edge) by questionnaire survey, asking cat owners to record all prey items returned by their cats. A total of 43 prey items were returned, 42% of which were small mammals, 30% invertebrates, 12% reptiles, 9% amphibians and 7% birds. Combining these data with two similar survey studies carried out in Cape Town I estimated that a total of 118 cats caught an average of 0.04 prey items per cat per day. Ten of the 13 cats were also monitored for 3 weeks using kitty-cam video cameras. Participating cats wore a video camera and all activity was analysed for prey captures and behavioural activity patterns.
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Winters, Amanda. "Effects of Warming and Predation on Invertebrate Activity." Bowling Green State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1499357799174464.
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Taylor, Justin Blake. "Deterring Rodent Seed Predation Using Seed-Coating Technologies." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/9045.
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With many natural landscapes undergoing restoration efforts, there is a growing need for the optimization of direct seeding practices. Seeds planted on wildlands are often consumed by rodents leading to reduced plant establishment. Coating seeds in rodent aversive products may prevent seed predation. We tested ten seed-coating formulations containing products expected to deter rodents, namely: ghost and cayenne pepper powders; essential oils from bergamot, neem, and pine; methyl-nonyl-ketone, anthraquinone, activated carbon, beta-cyclodextrin and a blank coating containing no rodent deterrents to serve as a control treatment. Each treatment was applied to Pseudoroegneria spicata (bluebunch wheatgrass) seeds. These seeds germinated similarly to uncoated control seeds unless the coating contained methyl-nonyl-ketone which reduced germination. Seeds were offered to Ord's kangaroo rats (Dipodomys ordii) that strongly avoided the treatments in favor of uncoated control seeds. Notably, the blank coating, lacking active ingredients, still elicited 99% avoidance. However, these results indicated behavior when alternative food sources are readily available, a scenario rare in nature. To address this, a second feeding experiment was conducted to observe D. ordii's behavior under calorie-restricted conditions. D. ordii were subjected to a fast period and then offered only one treatment. Under these conditions, many subjects chose to consume coated seeds, but to a lesser degree than subjects offered control seeds. Seeds coated in ghost pepper, neem oil, and activated carbon reduced consumption by 47-50%. Given these lab results, we would expect these seed-coatings to increase the establishment of native seeds following the direct seeding of wildlands by deterring rodent seed-predation.
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Smith, Dustin M. "Habitat selection and predation risk in larval lampreys." Morgantown, W. Va. : [West Virginia University Libraries], 2009. http://hdl.handle.net/10450/10493.
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Collumb, Christopher J. "Mesozooplankton population dynamics : factors affecting reproduction and predation /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Lohrey, Anne K. "The Impact of Avian Predation on the Brush-Legged Wolf Spider, Schizocosa Ocreata (Hentz), and Anti-Predator Responses to Avian Cues." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1195846324.
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Schel, Anne Marijke. "Anti-predator behaviour of Guereza colobus monkeys (Colobus guerez) /." Thesis, University of St Andrews, 2009. http://hdl.handle.net/10023/832.
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Black-and-white colobus monkeys are renowned for their impressive vocal behaviour, but up to date there have been only very few systematic efforts to study this. These monkeys are able to produce loud and low-pitched roars that transmit over long distances, which has lead to the assumption that these calls function in inter-group spacing and male-male competition. The fact that the monkeys sometimes produce the same calls to predators as well, has not received much attention so far. This thesis presents a detailed description of the form and function of the anti-predator behaviour of one species of black-and-white colobus monkeys, the Guereza (Colobus guereza), with a specific focus on their alarm calling behaviour. A second aim was to determine the effects of predator experience on their anti-predator behaviour, with a specific focus on call comprehension and production. Data were collected from two populations of Guereza monkeys in the Budongo Forest Reserve, Uganda, that differ in predation pressures experienced by their main predators: leopards, eagles and chimpanzees. Results showed that Guerezas use a basic form of zoo-syntax in order to compose predator-specific call sequences that vary in the number of roaring phrases and snorts. These sequences are meaningful to recipients, at least at the level of the predator class, but there were also indications for additional levels of encoded information: Guerezas appear to have evolved a second system, based on acoustic variants of individual phrases, which allows them to narrow down the information content of call sequences, generating the potential to communicate highly specific information by using a mix of syntactic and semantic cues. The monkeys’ vocal behaviour was influenced by predator experience, but not strongly so. Monkeys without prior experience with leopards lacked some of the behavioural nuances seen in leopard-experienced monkeys, but they nevertheless responded appropriately to visual and acoustic leopard models, suggesting they had retained the basic capacities to recognise this predator type as relevant and dangerous. Results are discussed in light of the comparative approach to the study of human language evolution. Although human language is unique in a number of ways, for example through its use of complex syntax and intentional semantics, some animal communication systems have revealed similar features, and Guerezas, the first member of the colobine family to be studied in this respect, are no exception. The Guerezas’ alarm calling behaviour is complex and flexible, and these monkeys have provided another piece of empirical evidence that is directly relevant for the comparative approach to human language evolution.
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Carter, Stephen Paul. "Habitat refuges and the management of predators for conservation." Thesis, Royal Holloway, University of London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269793.
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Stanford, Angela. "Rodent ecology and seed predation in logged and unlogged forest, Uganda." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324417.
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White, Joseph Douglas Mandla. "Seed predation and potential dispersal of Ceratocaryum argenteum (Restionaceae) nuts by the striped mouse (Rhabdomys pumilio) / Joseph Douglas Mandla White." Bachelor's thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/14027.
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This study aimed to better understand the role of rodents as seed predators and dispersers in the fynbos biome at De Hoop Nature Reserve, South Africa in May and June, 2013. Based on previous studies I hypothesised that the large, nut-like seeds of Ceratocaryum argenteum (Restionaceae) are scatter-hoarded by rodents and that rodent seed choices and seed fates are affected by seed size and hull thickness. Field trials using three seed types showed that smaller seeds with a high reward and low processing cost were consumed significantly(p<0.01) more than large, thick hulled seeds. Application of wire tags to facilitate discovery of relocated seeds had no significant influence on seed choice (p>0.05), but further research should be conducted to determine if spooling of C. argenteum seeds influences rodent seed choice. Smaller seeds with a high-reward and low processing cost showed a significantly greater percentage of usage (p<0.01) where seed stations were encountered and exploited. Rhabdomys pumilio was confirmed as being the most common murid at the study site, however, it seems unlikely that it scatter-hoards C. argenteum seeds, as no consumption or burial of seeds was observed. However, R. pumilio did show an interest in C. argenteum seeds and attempted to consume some seeds or carried seeds over distances not significantly different (p>0.05) from the observed distances between nearest neighbour C.argenteum plants before discarding them on the soil. Additionally, the maximum distance R. pumilio moved C. argenteum seeds was commensurate with the maximum distance between nearest neighbour C. argenteum stands, so the end fate of the seeds remains unknown. Further research should account for seasonal variability in scatter-hoarding behaviour.
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Slater, Graham James. "Biomechanical adaptations to predation in the carnivoran craniofacial skeleton." Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1997615301&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Chung, Pik-shan. "Post-dispersal seed predation by rats in Hong Kong." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B3617564X.
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Öhlund, Gunnar. "Ecological and evolutionary effects of predation in environmental gradients." Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-59465.
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Understanding species interactions and how they affect densities and distributions of organisms is a central theme in ecological research. Studying such interactions in an ecosystem context is challenging as they often depend on species-specific characteristics and rates that not only change during the ontogeny of an organism, but also are affected by the surrounding environment. This thesis focuses on two separate questions and study systems that highlight different aspects of how effects of predation can depend on environmental conditions. In the first part of the thesis, we studied how temperature affects attack rate and handling time, two ecological rates with profound importance for predator-prey dynamics. Using a metaanalysis, we first show that the currently dominating model for temperature dependence in predator-prey interactions, i.e. the Arrhenius equation, has weak support in available empirical literature. This suggests that we need new rules for how and when we can generalize on the temperature-dependence of intake rates. We then use a simple model and a series of experiments to demonstrate that differences in the relative physiological capacity between predator and prey can impose strong non-linear effects on temperature-response curves of attack rate. In the second part of the thesis, we study the role of predation along a benthic-pelagic habitat gradient in promoting divergence and resource polymorphism among prey. We show that presence of a large piscivorous predator, the northern pike (Esox lucius), induces dwarfs, giants or divergence into both ecotypes in populations of European whitefish (Coregonus lavaretus) depending on lake characteristics. Using dated introductions of whitefish as controlled natural experiments, we show that pike presence induces rapid life history divergence between pelagic and littoral habitat use strategies, and that this divergence can translate into partial reproductive isolation in a matter of decades. Our results demonstrate the potential for thresholds in a crucial ecological rate, setting the stage for tipping points with potentially far reaching implications for effects of warming on predator prey dynamics and ecosystem stability. Moreover, they illustrate the potentially drastic consequences of such tipping points by demonstrating the importance of a single predator species as a driving force behind the creation and maintenance of biodiversity in a natural system.
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Hughes, Nelika Karen Biological Earth & Environmental Sciences Faculty of Science UNSW. "Dangerous liaisons: the predation risks of receiving olfactory signals." Publisher:University of New South Wales. Biological, Earth & Environmental Sciences, 2009. http://handle.unsw.edu.au/1959.4/43315.
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Individuals are at risk when communicating because conspicuous signals attract both conspecifics and eavesdropping predators. This predation cost of communicating has typically been attributed to signalling individuals because of their conspicuous role. But if predators are attracted to signals, then receivers, both intended or otherwise, may also find themselves at risk of predation. In this thesis, I used olfactorily communicating house mice Mus domesticus to address several key questions regarding the predation risks to receivers of conspecific signals. Using field experiments, I established that several predator species are rapidly attracted to the scent signals of their mouse prey. Male house mice were sensitive to this risk of predation when receiving conspecific signals. Mice traded off the predation risks of receiving with the perceived social value of a conspecific scent signal, however, and were more willing to receive signals of high social value than those of low social value when in the presence of a predation cue. But mice did not relinquish all antipredatory behaviours to receive signals. Instead, spatial point pattern analyses revealed that they used small-scale changes in space use to maintain receiving rates of conspecific signals, while minimising excess movements likely to attract a predator??s attention. Mice were also sensitive to the risks posed by scents in different spatial configurations. They perceived patchily distributed scents as more risky than randomly or regularly distributed scents, highlighting the importance of considering scale when examining predator:prey interactions. I further extended the concept of risky receiving to show that it includes interspecific eavesdropping ?? greatly generalising our concept of the landscape of fear. In a final laboratory experiment, I reveal a mechanism for the otherwise maladaptive maintenance of receiving under predation risk. The effects of social isolation on aggressive and anti-social behaviours were gradually attenuated by exposing male mice to the scents of an increasing number of conspecifics, despite a lack of physical contact. Thus, while prey are sensitive to the increased risks of predation when receiving con- and hetero-specific signals, they must balance this risk against the perceived social benefits of receiving a signal, and the potentially severe social costs of not doing so.
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Cleveland, Shawn M. "HUMAN PREDATION RISK AND ELK BEHAVIOR IN HETEROGENEOUS LANDSCAPES." The University of Montana, 2010. http://etd.lib.umt.edu/theses/available/etd-04282010-103245/.
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Elk (Cervus elaphus) are increasing in fragmented landscapes that result from exurban human development throughout western North America. This problem is increasing human-wildlife conflicts and represents a significant new challenge to wildlife managers. Elk hunting must be intensively managed, if allowed at all, to reduce public relations problems. For example, the Montana Department of Fish, Wildlife & Parks has focused three hunts on a rapidly growing (~11% annually) elk herd in the wildland-urban interface (WUI) of Missoula, Montana, USA. Their goals were to reduce population growth rate, crop depredation, and habituation to humans. However, little was known about the indirect effect hunting has on anti-predator behavior, movement, resource selection, and human-elk conflicts. We first investigated the indirect effects of hunting on elk using an extensive comparison of elk anti-predator behavior across four human predation risk levels in western Montana. We collected 361behavioral observations across this predation risk gradient from October 2008 to March 2009. Vigilance was highest in highest predation risk areas and lowest in lowest risk areas. Vigilance and movement attenuated with the removal of human predation risk within 3-5 weeks under intermediate human predation risk in Missoula, Montana. I then used an intensive investigation of elk outfitted with global positioning system (GPS) collars in the WUI of Missoula to test the indirect effects of hunting on elk. We used data from nine GPS collared adult female elk during three hunting seasons with increasing hunting pressure (2007-2009) to test relationships between movement rates measured by first passage time (FPT) and resource selection. FPT decreased annually, by season type, and by hunting mode (archery vs rifle), and was negatively correlated with hunter predation risk. Elk slowed down ~750 meters from and selected for areas ~1200 meters from houses and trails, suggesting habituation to humans contributed to WUI human-wildlife conflict. These results support the risk allocation hypothesis that elk modify behavior in relation to temporal and spatial variation in human predation risk, and provide some of the first insights as to the indirect effects of hunting on elk in the WUI.
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DeBlois, Elisabeth M. "Invertebrate predation on the benthic eggs of marine fish." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39387.
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The character and magnitude of predation by Calliopius laeviusculus on the intertidal eggs of capelin (Mallotus villosus) were examined. Average endobenthic densities at Bryant's Cove (NFLD) in 1988 for both amphipods and capelin eggs during capelin egg development (June 17-August 8) were 0.78 amphipods cm$ sp{-2}$ and 62 eggs cm$ sp{-3}$ (750 cm$ sp{-2}$) respectively. At this average capelin egg density, laboratory results suggest that, on a daily basis, only gut capacity and clearance time limit amphipod predation on eggs. In situ, C. laeviusculus biomass closely tracked capelin egg biomass indicating that reproductive cues operating for both capelin and amphipods may be linked. In 1988, ca. 50% of the annual production of C. laeviusculus resulted from predation on capelin eggs. Given the bioenergetic demands of C. laeviusculus and the annual variation in capelin spawning effort, the temporal overlap between capelin eggs and high amphipod biomass could result in predation mortalities ranging from ca. 15-30% of the total capelin egg deposition.