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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Factors affecting proximate composition of prey species important to marine vertebrate predators in the Northwestern Atlantic /

Magalhães, Alexandra Mesquita, January 1999 (has links)
Thesis (M. Sc.), Memorial University of Newfoundland, 1999. / Bibliography: p. 17-32.
12

Behavioural plasticity of life history traits in the New Zealand avifauna : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Zoology /

Starling, Amanda. January 2006 (has links)
Thesis (M. Sc.)--University of Canterbury, 2006. / Typescript (photocopy). Includes bibliographical references. Also available via the World Wide Web.
13

The cognitive dimensions of a biological hazard: A study of livestock predation in British Columbia within a hazards framework

Wilkerson, Orland Lee 29 June 2018 (has links)
This study focuses on the cognitive dimensions of two important aspects of the predator-livestock problem in British Columbia: the concrete coping strategies adopted by individual livestock producers and the institutional responses adopted by, or available to, the Provincial Wildlife Branch. The threat posed to domestic stock by wild predators is conceptualized as a biological hazard, and the advantages of this approach are discussed. A conceptual framework integrating theoretical insights from geography, social psychology, psychology, and political science is developed. Several hypotheses are derived from this framework, and a number of these are linked to form two conceptual models, one designed for an analysis of ranchers' cognitions, the other for the examination of nonranchers' cognitions. Both models relate several cognitive variables to the perceived acceptability of a number of lethal methods of wolf control. These variables include: ecological orientation (as measured by the New Environmental Paradigm Scale); attitudes towards wolves; and perceptions of the wolf threat. Two mail survey questionnaires were developed, one (Version A) for nonranchers, the other (Version B) for ranchers. Version A was satisfactorily completed by a total of 574 respondents: 259 from the city of Victoria; 95 from Williams Lake; 87 from Kamloops; and 133 from the Northwest Wildlife Preservation Society (NWWPS). The data from the three urban samples were combined to form a "general public" sample. Version B was completed by 283 ranchers. Questionnaire data were supplemented by the content analysis of several relevant documents and informal interviews with selected personnel from the B.C. Wildlife Branch, the ranching community, and a number of wildlife interest groups. A variety of statistical techniques, including simple correlation, multiple regression, analysis of covariance, and discriminant analysis, were used to analyze the data. The analyses provided strong support for most of the hypotheses. Several of the more important findings are noted here. For all three sample groups (general public, ranchers, and NWWPS), significant relationships were found between ecological orientation and attitudes towards wolves; between attitudes towards wolves and perceptions of the threat that wolves pose to individual cattle producers and the cattle industry as a whole; between attitudes towards wolves and the acceptability of certain lethal wolf control measures; and for nonranchers, between attitudes towards wolves and the perceived humaneness of lethal wolf control, and between the perceived humaneness of lethal wolf control and the acceptability of lethal wolf control. A number of variables exhibited significant differences across the groups: ecological orientation; attitudes towards woIves; and perceptions of the wolf, coyote, and bear threats. Several management implications suggested by the research are discussed and a number of policy recommendations and suggestions for further research are offered. / Graduate
14

The predatory behavior of Pisaster ochraceus (Brandt)

Jillson, David A. 01 January 1973 (has links) (PDF)
The persistence of predator-prey systems in evolutionar time is a function of the efficiency with which the predator obtains its food, and the ability of the prey to avoid ex- tinction. One of the important components of survival of the system is environmental heterogeneity (Huffaker 1958). Along rocky intertidal regions of the northern Pacific coast of North America, a major predator, the starfish Pisast ochraceus has a dominant effect upon patterns of distribution of many intertidal organisms (Paine 1966). Likewise, the distribution of intertidal fauna exert an effect upon the activities of Pisaster. Other biological interactions such an grazing activities of limpets and predatory behavior of emails also affect the intertidal distribution of species (Connell 1961, 1970, Dayton 1971).
15

Predator biomass and habitat characteristics affect the magnitude of consumptive and non-consumptive effects (NCEs): experiments between blue crabs, mud crabs, and oyster prey

Hill, Jennifer Marie 01 July 2011 (has links)
Recent research has focused on the non-lethal effects of predator intimidation and fear, dubbed non-consumptive effects (NCEs), in which prey actively change their behavior and habitat use in response to predator chemical cues. Although NCEs can have large impacts on community structure, many studies have ignored differences in predator population structure and properties of the natural environment that may modify the magnitude and importance of NCEs. Here, I investigated the roles of predator size and density (i.e. biomass), as well as habitat characteristics, on predator risk assessment and the magnitude of consumptive and NCEs using blue crabs, mud crabs, and oyster prey as a model system. Predation experiments between blue crabs and mud crabs demonstrated that blue crabs consume mud crabs; however, the consumptive effects were dependent upon blue crab body size and habitat type. When mud crabs were exposed to chemical cues from differing biomasses of blue crabs in laboratory mesocosms, mud crab activity and predation on oysters was decreased in response to high biomass treatments (i.e. large and multiple small blue crabs), but not to low biomass predators (i.e single small blue crab), suggesting that risk associated with predator size is perceptible via chemical cues and is based on predator biomass. Further experiments showed that the perception of risk and the magnitude of the NCEs were affected by the sensory cues available and the diet of the blue crab predator. The NCE based on blue crab biomass was also demonstrated in the field where water flow can disperse cues necessary for propagating NCEs. Properties of water flow were measured within the experimental design and during the experiment and confirmed cage environments were representative of natural conditions and that patterns in NCEs were not associated with flow characteristics. These results affect species conservation and commercial fisheries management and demonstrate that we cannot successfully predict NCEs without considering predator size structure and the contexts under which we determine predator risk.
16

Snowy Plover Demography in Oregon

Gaines, Eleanor Prindiville 03 June 2019 (has links)
A thorough understanding of demographic parameters and their contribution to overall population growth is fundamental to effective conservation of small populations, but this information is often lacking. The Pacific Coast population of the Western Snowy Plover (Charadrius nivosus nivosus) is listed as threatened and has been the target of long-term, multi-pronged management in Oregon. The Oregon coastal population has been intensively monitored since 1990, and over 80% of the population is color banded, but a comprehensive analysis of demographic parameters and the effect of management on vital rates and population growth has been unavailable until now. Here, the author used capture-mark-resight techniques to document survival at each life stage and to explore environmental and management factors that best explained variation in survival over a 25-year study period. The author analyzed the effects of habitat restoration, exclosure use, and lethal predator management on survival at appropriate life stages and evaluated the effects of one management option, lethal predator control, on overall population growth. Chick survival to fledging improved dramatically after the chicks' 5th day, was higher in years with lethal predator management, and was highest during the peak of the long brood-rearing season. Cold weather, particularly during the chicks' first 5 days, had a negative effect on survival to fledging. Juvenile survival from fledging to the following spring declined over the study period, but rebounded after implementation of lethal predator management. Adult survival was lower in wetter-than-average winters and higher in years with predator management. The author used the survival analyses and productivity data collected over 25 years in a matrix population model to reveal that population growth is most sensitive to changes in adult survival, and that while predator management is important for continued growth, its use may be scaled back by as much as 50% and still maintain a growing population. My results, encompassing all phases of this species' life cycle, demonstrate that with holistic and thoughtful adaptive management, and with the cooperation of numerous agencies, a balance can be struck between protection and control of native species to bring about recovery of species threatened with (local) extinction.
17

Movements, population dynamics and predatory behaviour of stoats inhabiting alpine grasslands in Fiordland

Smith, Derek, n/a January 2006 (has links)
Stoats are introduced mammalian carnivores implicated in the decline of several of New Zealand�s endemic species. Most research into stoats in New Zealand has focused on beech forest habitat, especially in years of peak stoat abundance following heavy beech seedfall and peak cohorts of mice. In New Zealand, alpine grasslands occur above the altitudinal limit of beech forest (900-1000 m a.s.l.). Although previous research has shown stoats to be present there, little is known about the ecology of stoats in alpine grasslands. This research aimed to test whether alpine grasslands were a marginal habitat occupied by surplus stoats that had spilled over from beech forest populations, i.e. a sink habitat. The alternative is that alpine grasslands are a desirable habitat deliberately exploited by stoats. This question was answered using mark-recapture, radio-tracking, diet analysis and a food addition experiment. Another objective was to determine whether nest survival is higher in alpine grassland compared to beech forest and whether stoats are likely to be a frequent predator of ground nests in alpine grasslands relative to other introduced mammals that inhabit them. If nest survival is higher in alpine grassland then alpine grasslands may be a refuge from predation. However, if it is not then it is important for management to know the relative risk posed by stoats compared with other predators. An artificial nest experiment was used to answer these questions. This research was undertaken during two years of low to intermediate beech seedfall and therefore provided an opportunity to look at the ecology of stoats in a New Zealand National Park outside years of peak abundance. The principal study site for this research was the Borland Valley, Fiordland National Park. Compositional analysis showed that stoats in alpine grassland selected for it over adjacent beech forest. The range cores of these stoats were high up in alpine grassland away from the ecotone with beech forest. Stoats occurred at similar densities in alpine grasslands as they did in beech forest and observed survival was similar between the two habitats (with the exception of 2004 when it may have been higher in alpine grassland). The most frequent prey of stoats inhabiting beech forest were birds and mice. Although stoats in alpine grasslands also ate birds and mice their most frequent prey were ground weta and hare. Food addition appeared to cause diet switching but did not reduce the distances moved by stoats, suggesting that other factors may be more important in regulating their summer home range size in alpine grasslands. All of these factors lead to the conclusion that alpine grasslands in the Borland are not a marginal habitat for stoats, but may instead be a desirable one. Artificial nests had a higher probability of survival in alpine grassland compared to adjacent beech forest, but survival was too low to support the idea that alpine grasslands are a refuge. Stoats were the most frequent predator of artificial nests in both habitats, but 95 % confidence intervals overlapped the predation rate by possums, which was also high. These findings illustrate the need for a comprehensive landscape approach to stoat control in montane National Parks, for two reasons: 1) endemic biodiversity in alpine grasslands may be under threat from stoat predation, 2) alpine grasslands may act as a source for dispersing stoats that reinvade lowland stoat control areas. In the absence of heavy beech seedfall and peak mouse abundance, stoats occurred at densities of around 1 km⁻� in both habitats and there was recruitment into these populations. This raises the important question: What regulates the distribution and abundance of stoats in years of low beech seedfall and low mouse abundance? In these years birds, ground weta and hares may be as important as mice are in years of peak abundance following heavy beech seedfall.
18

Patterns and economic impacts of livestock predation in rural communities bordering Makgadikgadi Pans National Park in Botswana.

Dikobe, Leonard Mogopodi. January 1997 (has links)
Northern Botswana's rural agricultural settlements bordering national parks and game reserves. In two study areas (Khumaga and Gweta, bordering Makgadikgadi Pans National Park), spatial, temporal and prey-type patterns of livestock predation were assessed. Cattle, goats, horses, donkeys and sheep were the key livestock types. Lion, leopard, cheetah, wild dog, black-backed jackal, spotted hyena and the Nile crocodile (occurring only in Khumaga) were the key predators. Oral interviews with farmers in these villages provided insights into the patterns and impacts of livestock predation on rural economies. Khumaga's livestock predation scenario is dominated by lion predation on cattle, goats and donkeys, leopard predation on small stock and calves, and crocodile on goats. Wet season predation rates were higher than dry seasons', except for spotted hyena, black-backed jackal and leopard. Leopard and black-backed jackal are dominant small stock predators in Gweta. lion are the main cattle and donkey predators (though at lower frequencies). Dry season predation rates are higher. Farmers who own more livestock appear to lose more Northern Botswana's rural agricultural settlements bordering national parks and game reserves. In two study areas (Khumaga and Gweta, bordering Makgadikgadi Pans National Park), spatial, temporal and prey-type patterns of livestock predation were assessed. Cattle, goats, horses, donkeys and sheep were the key livestock types. Lion, leopard, cheetah, wild dog, black-backed jackal, spotted hyena and the Nile crocodile (occurring only in Khumaga) were the key predators. Oral interviews with farmers in these villages provided insights into the patterns and impacts of livestock predation on rural economies. Khumaga's livestock predation scenario is dominated by lion predation on cattle, goats and donkeys, leopard predation on small stock and calves, and crocodile on goats. Wet season predation rates were higher than dry seasons', except for spotted hyena, black-backed jackal and leopard. Leopard and black-backed jackal are dominant small stock predators in Gweta. lion are the main cattle and donkey predators (though at lower frequencies). Dry season predation rates are higher. Farmers who own more livestock appear to lose more cattle than those who own few. Gweta contrasts with Khumaga, having livestock predation highest during dry seasons, less reduction in livestock sales and a lower value of pending compensation claims. These predation patterns synchronise with movements of zebra and wildebeest to and from the Boteti river. Losses of livestock affect the utility derived from livestock and monetary gains from direct sales. Costs due to loss of biodiversity, though not quantified, add to those borne by the State through predator control. Both the State and the farmers loose. These losses reduce the incentives of the latter to conserve species that contribute reduction in their returns. The issue of State expenditure on predator control illustrates the possible need for re-direction of such funds into farmer-based predator control, much as an integral part of the current southern African trend of community-based natural resource management. Key words: livestock predation, predator control, economics, conservation, Botswana. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1997.
19

Movements, population dynamics and predatory behaviour of stoats inhabiting alpine grasslands in Fiordland

Smith, Derek, n/a January 2006 (has links)
Stoats are introduced mammalian carnivores implicated in the decline of several of New Zealand�s endemic species. Most research into stoats in New Zealand has focused on beech forest habitat, especially in years of peak stoat abundance following heavy beech seedfall and peak cohorts of mice. In New Zealand, alpine grasslands occur above the altitudinal limit of beech forest (900-1000 m a.s.l.). Although previous research has shown stoats to be present there, little is known about the ecology of stoats in alpine grasslands. This research aimed to test whether alpine grasslands were a marginal habitat occupied by surplus stoats that had spilled over from beech forest populations, i.e. a sink habitat. The alternative is that alpine grasslands are a desirable habitat deliberately exploited by stoats. This question was answered using mark-recapture, radio-tracking, diet analysis and a food addition experiment. Another objective was to determine whether nest survival is higher in alpine grassland compared to beech forest and whether stoats are likely to be a frequent predator of ground nests in alpine grasslands relative to other introduced mammals that inhabit them. If nest survival is higher in alpine grassland then alpine grasslands may be a refuge from predation. However, if it is not then it is important for management to know the relative risk posed by stoats compared with other predators. An artificial nest experiment was used to answer these questions. This research was undertaken during two years of low to intermediate beech seedfall and therefore provided an opportunity to look at the ecology of stoats in a New Zealand National Park outside years of peak abundance. The principal study site for this research was the Borland Valley, Fiordland National Park. Compositional analysis showed that stoats in alpine grassland selected for it over adjacent beech forest. The range cores of these stoats were high up in alpine grassland away from the ecotone with beech forest. Stoats occurred at similar densities in alpine grasslands as they did in beech forest and observed survival was similar between the two habitats (with the exception of 2004 when it may have been higher in alpine grassland). The most frequent prey of stoats inhabiting beech forest were birds and mice. Although stoats in alpine grasslands also ate birds and mice their most frequent prey were ground weta and hare. Food addition appeared to cause diet switching but did not reduce the distances moved by stoats, suggesting that other factors may be more important in regulating their summer home range size in alpine grasslands. All of these factors lead to the conclusion that alpine grasslands in the Borland are not a marginal habitat for stoats, but may instead be a desirable one. Artificial nests had a higher probability of survival in alpine grassland compared to adjacent beech forest, but survival was too low to support the idea that alpine grasslands are a refuge. Stoats were the most frequent predator of artificial nests in both habitats, but 95 % confidence intervals overlapped the predation rate by possums, which was also high. These findings illustrate the need for a comprehensive landscape approach to stoat control in montane National Parks, for two reasons: 1) endemic biodiversity in alpine grasslands may be under threat from stoat predation, 2) alpine grasslands may act as a source for dispersing stoats that reinvade lowland stoat control areas. In the absence of heavy beech seedfall and peak mouse abundance, stoats occurred at densities of around 1 km⁻� in both habitats and there was recruitment into these populations. This raises the important question: What regulates the distribution and abundance of stoats in years of low beech seedfall and low mouse abundance? In these years birds, ground weta and hares may be as important as mice are in years of peak abundance following heavy beech seedfall.
20

Options for eland: a multi-scale assessment of antipredatory responses of a vulnerable prey species to their dominant predator in the Eastern Cape, South Africa

Leaver, Jessica January 2014 (has links)
Eland Tragelaphus oryx are the largest and slowest African antelope, falling within the preferred weight range of the prey of lions Panthera leo. Little is known, however, about the antipredatory strategies employed by eland. Rapid population declines in several small reserves following the reintroduction of lions suggest that the antipredatory strategies of eland may be compromised in spatially limited areas. This emphasises the need for research aimed at investigating how eland respond to lions, particularly in the spatial context, given that lions are increasingly being reintroduced into small reserves in South Africa. This study aimed to investigate lion-eland interactions at multiple scales and determine where on the landscape eland were vulnerable to predation. Adult female eland (n = 3 per site) in breeding herds were collared with GPS satellite collars in two study sites; the Nyathi section of Addo Elephant National Park (Nyathi) and Mountain Zebra National Park (MZNP) in the Eastern Cape, South Africa. A reintroduced population of lions, comprising two males and one female, was present in each study site, with individuals fitted with GPS satellite collars. At a broad spatiotemporal scale, eland did not avoid lions and there was considerable overlap between eland and lion home ranges in both study sites. At a finer spatiotemporal scale however, eland and lion space use was asynchronous in time, except in the case of the female lion in Nyathi where there was considerable overlap at the finest temporal scale investigated (i.e. monthly). Herd-associated eland in Nyathi were killed most frequently in areas associated with high long-term use by the female lion, showing that failure to avoid the female lion at a fine scale increased predation risk for eland. Secondly, eland in Nyathi were killed most frequently in habitat types of intermediate structural density (i.e. mixed habitats), which limited the viewshed of eland but presumably offered increased forage. This habitat type was selected for by eland, despite it being associated with a higher level of predation risk. This suggested that eland in Nyathi traded off safety for forage. In MZNP, predation of herd-associated eland was low which reflected the limited spatial overlap between eland and lion at a fine scale in this reserve. In Nyathi, but not in MZNP, eland responded to lions within 1.5 km by increasing their movement rate, with this response particularly strong at night. The findings of this study show that eland responses to lions are scale-dependent and site-specific. Furthermore, eland responses to lions were shown to be lion gender-specific. This study has increased our understanding of the antipredatory behaviours of eland and demonstrated the importance of investigating prey responses to predation risk at multiple scales.

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