Large Carnivore Behavior and Intraguild Interactions Under Anthropogenic Influence

• Main Author: Robins, Clint W
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2023
• Subjects: Ecology; Environmental science; Forestry; Wildlife Conservation; Wildlife Management
• ISBN: 9798379410308

Among the many human activities that affect wildlife, urbanization is one of the most prominent sources of species extinction and biodiversity loss. Responses to urbanization vary across taxa, with large carnivores being particularly sensitive to this process owing to their space needs and energy requirements. Not surprisingly, therefore, large carnivore declines in the face of urbanization are well documented but changes to the behavior and ecology of species that are able to persist in built environments have received less attention. In the state of Washington, sympatric cougar (Puma concolor) and American black bear (Ursus americanus) populations overlap with wildland and residential landscapes, providing a rare opportunity to evaluate the behavioral responses of multiple large carnivores to urbanization. Accordingly, this dissertation examines how various forms of anthropogenic disturbance linked with urbanization impact large carnivore behavior and interspecific interactions, with the broader goal of improving our understanding of the mechanisms driving changes to the ecology of large predators as they must increasingly navigate a human-dominated world. In Chapter 1, I provide justification for large carnivore research in urban environments. In Chapter 2, I explore changes to individual and population niche breadth in black bears as a function of residential development. I demonstrate using resource utilization functions (RUFs) that bear population-level use increased significantly as distance to residential mature forest, lakes, and rivers decreased. Black bears exhibited high individual variation in both residential and wildland landscapes. Nevertheless, black bear use near mature forest differed significantly between residential and wildland landscapes as bears began to enter hyperphagia and use near residential mature forest and residential rivers differed between females and males in summer. In Chapter 3, I once again employ RUFs to evaluate resource use by black bears navigating managed forests in western Washington with (Snoqualmie Forest) and without (Department of Natural Resources lands) diversionary feeding during fed and non-fed portions of the year to shed light on large carnivore responses to human subsidies in areas just beyond the urban fringe. Black bear use of young forest stands (15-30 years), as well as other landscape attributes, was similar between managed forests with and without feeding stations irrespective of whether supplemental food was supplied. Notably, individual variation was significant for nearly every covariate in both forests, with bears often demonstrating contrasting patterns of use, effectively washing out any population-level effects of diversionary feeding and harvest intensity on resource use. In Chapter 4, I explore whether residential development in the form of housing density (residences/ha), along with demographic and environmental covariates, impact the propensity for black bears to scavenge cougar-killed prey along western Washington’s wildland-urban gradient. The summer season and housing density were significant negative predictors of black bear scavenging, and cougar handling time was a significant positive predictor of bear carcass visitation. Overall, my results reveal that residential development can modify population-wide black bear behavior in ways that may shape patterns of human-wildlife interaction even though individual bear responses to anthropogenic disturbance often vary. My results also suggest that the impact of urbanization on interspecific relationships among large carnivores can be dramatic, as even modest levels of residential development all but eliminated black bear scavenging on cougar kills. This dissertation provides novel insights into predator-predator interactions in residential landscapes and advances our understanding of the myriad ways residential development may disrupt interactions within carnivore guilds, creating avenues of further study into the mechanisms structuring urban wildlife communities.