Graduate Theses & Dissertations

cascading effects of risk in the wild
Predation risk can elicit a range of responses in prey, but to date little is known about breadth of potential responses that may arise under realistic field conditions and how such responses are linked, leaving a fragmented picture of risk-related consequences on individuals. We increased predation risk in free-ranging snowshoe hares (Lepus americanus) during two consecutive summers by simulating natural chases using a model predator (i.e., domestic dog), and monitored hare stress physiology, energy expenditure, behaviour, condition, and habitat use. We show that higher levels of risk elicited marked changes in physiological stress metrics including sustained high levels of free plasma cortisol which had cascading effects on glucose, and immunology, but not condition. Risk-augmented hares also had lowered daily energy expenditure, spent more time foraging, and decreased rest, vigilance, and travel. It is possible that these alterations allowed risk-exposed hares to increase their condition at the same rate as controls. Additionally, risk-augmented hares selected, had high fidelity to, and were more mobile in structurally dense habitat (i.e., shrubs) which provided them additional cover from predators. They also used more open habitat (i.e., conifer) differently based on locale within the home range, using familiar conifer areas within cores for rest while moving through unfamiliar conifer areas in the periphery. Overall, these findings show that prey can have a multi-faceted, highly plastic response in the face of risk and can mitigate the effects of their stress physiology given the right environmental conditions. Author Keywords: behaviour, condition, daily energy expenditure, predator-prey interactions, snowshoe hare, stress physiology
Beyond Habitat
My objective was to understand how individual variation, in conjunction with variation in habitat, can affect individual and population-level variation in animal space use. I used coyotes (Canis latrans) as a model species to investigate the roles of hybridization, an inherited intrinsic factor, and spatial memory, a learned intrinsic factor, on space use. I used a diversity of methods and approaches, including meta-regression, multiple imputation, simulations, resource selection functions, step selection functions, net-squared displacement analysis, and survival analysis. A major contribution was my investigation of the performance of multiple imputation in a meta-regression framework in Chapter 2. My simulations indicated that multiple imputation performs well in estimating missing data within a meta-regression framework in most situations. In Chapter 3, I used published studies of coyote home range size in a meta-regression analysis with multiple imputation to examine the relative roles of hybridization and environmental variables on coyote home range size across North America. I found that hybridization with Canis species was a leading factor driving variation in coyote space use at a continental scale. In Chapter 4, I used telemetry data for 62 coyotes in Newfoundland, Canada, to investigate the influence of cognitive maps on resource use. I found that resident coyotes used spatial memory of the landscape to select or avoid resources at spatial scales beyond their immediate sensory perception relative to transient coyotes, presumably increasing their fitness. Taken together, my dissertation demonstrates that intrinsic factors, such as genetic ancestry and spatial memory, can have substantial influences on how animals use space at both individual and population levels, and at both a local and a continental scales. Author Keywords: canis latrans, hybridization, meta-regression, multiple imputation, Newfoundland, spatial memory
Demography and habitat selection of Newfoundland caribou
The objective of this thesis is to better understand the demography and habitat selection of Newfoundland caribou. Chapter 1 provides a general introduction of elements of population ecology and behavioural ecology discussed in the thesis. In Chapter 2, I examine the causes of long-term fluctuations among caribou herds. My findings indicate that winter severity and density-dependent degradation of summer range quality offer partial explanations for the observed patterns of population change. In Chapter 3, I investigate the influence of climate, predation and density-dependence on cause-specific neonate survival. I found that when caribou populations are in a period of increase, predation from coyotes and bears is most strongly influenced by the abiotic conditions that precede calving. However, when populations begin to decline, weather conditions during calving also influenced survival. I build on this analysis in Chapter 4 by determining the influence of climate change on the interplay between predation risk and neonate survival. I found that the relative equilibrium between bears and coyotes may not persist in the future as risk from coyotes could increase due to climate change. In Chapter 5, I investigate the relationships in niche overlap between caribou and their predators and how this may influence differential predation risk by affecting encounter rates. For coyotes, seasonal changes in niche overlap mirrored variation in caribou calf risk, but had less association with the rate of encounter with calves. In contrast, changes in niche overlap during the calving season for black bears had little association with these parameters. In Chapter 6, I examine broad-level habitat selection of caribou to study trade-offs between predator avoidance and foraging during the calving season. The results suggest that caribou movements are oriented towards increased access to foraging and the reduction of encounter risk with bears, and to a lesser extent, coyotes. Finally, I synthesize the major findings from this thesis and their relevance to caribou conservation in Chapter 7, to infer that Newfoundland caribou decline is ultimately driven by extrinsic and intrinsic elements related to density-dependence. Reduction in neonate survival emerged from nutritionally-stressed caribou females producing calves with lower survival. Author Keywords: Behavioural ecology, Black bear (Ursus americanus), Coyote (Canis latrans), Population ecology, Predator-prey interactions, Woodland caribou (Rangifer tarandus)

Search Our Digital Collections

Query

Enabled Filters

  • (-) ≠ Farell
  • (-) ≠ Bell
  • (-) ≠ Theory, Culture and Politics
  • (-) = Schaefer
  • (-) = Murray
  • (-) = Doctor of Philosophy

Filter Results

Date

2010 - 2020
(decades)
Specify date range: Show
Format: 2020/01/21

Author Last Name

Last Name (Other)

Degree Discipline

Subject (Topic)