Dissertation Defence: Evaluating the mechanisms linking anthropogenic habitat alteration to caribou declines in western Canada

Melanie Dickie, supervised by Dr. Adam T Ford, will defend their dissertation titled “Evaluating the mechanisms linking anthropogenic habitat alteration to caribou declines in western Canada” in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Biology.

An abstract for Melanie Dickie’s dissertation is included below.

Defences are open to all members of the campus community as well as the general public. Registration is not required for in person defences.

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Abstract

The study of ecological systems requires a nuanced understanding of the complex interactions that govern species dynamics. In this dissertation I investigate the intricate relationships between habitat alteration, climate change, and predator-prey dynamics that drive species declines in western Canada’s boreal forest, namely of woodland caribou (Rangifer tarandus). I explore the roles of habitat alteration and climate in facilitating the expansion of white-tailed deer (Odocoileus virginianus), a novel apparent competitor to caribou (Chapter 2). I demonstrate that deer densities are primarily influenced by winter severity, though habitat alteration and productivity can mediate this effect, suggesting an interaction where milder winters and disturbed habitats combine to support higher deer densities. These findings emphasize the significant role of climate in determining population abundance, while also highlighting the compounding effects of habitat alteration. In Chapter 3 I examine how resource density and exploitation efficiency influence wolf (Canis lupus) home ranges, a primary predator of caribou. Wolf home ranges were smaller in areas with increased linear feature density, though this relationship was weaker in more productive areas, indicating that wolves benefit most from linear features in less productive environments. These results suggest that increased access to prey in disturbed landscapes can reduce the area wolves need to survive, potentially linking to wolf densities; reinforcing the indirect role of habitat alteration in predator-prey dynamics. In Chapter 4, I synthesize existing knowledge on how the effects linear features cascade through the food web associated with caribou declines. While many studies explore how linear features affect the spatial behavior of caribou, their predators, and prey, few directly connect these changes to caribou demographic outcomes. This gap underscores the need for targeted research to inform effective conservation strategies and targets for woodland caribou. Additionally, I explore the response of prey species to predator reductions aimed to reduce predation on caribou, finding only a muted behavioral and demographic response by white-tailed deer, moose and caribou; offering a deeper appreciation of complexities of the ecological mechanisms at play. Finally, I provide a suggested path forward for accommodating uncertainty within adaptive management plans when species are in precipitous declines; Intervention-forward adaptive management. Throughout my dissertation, I emphasize the importance of advancing ecological theory to better comprehend the variability and context-dependence of natural systems, ultimately contributing to more effective conservation strategies.