Thesis Defence: Spatial Variation in Grizzly Bear Diet Across British Columbia

Jonathan VanElslander, supervised by Dr. Mathieu Bourbonnais, will defend their thesis titled “Spatial Variation in Grizzly Bear Diet Across British Columbia” in partial fulfillment of the requirements for the degree of Master of Science in Earth and Environmental Sciences.

An abstract for Jonathan VanElslander’s thesis is included below.

Defences are open to all members of the campus community as well as the general public. Please email mathieu.bourbonnais@ubc.ca to receive the Zoom link for this defence.

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ABSTRACT

Dietary niche variation is a key facet of an animal’s niche and can be a driver of spatial variation in behaviour, population dynamics, and sensitivity to anthropogenic threats. Spatial assessments of the variation of an animal’s dietary niche helps provide key baseline knowledge for the research and management of a species, and are particularly important for species with large geographic ranges and highly variable niches. Grizzly bears (Ursus arctos) are a wide-ranging omnivorous mammal with enormous dietary flexibility and a species of concern in Canada. I estimated the proportion of vegetation, terrestrial meat, anadromous salmon, and non-anadromous kokanee salmon in the diet of over 1800 grizzly bears via stable isotope analyses of over 2500 guard hair samples collected across the province of British Columbia. Using these estimates, I created fine-scale maps of grizzly bear diet using a parametric generalized additive mixed effects model with spatial random fields. The results of these predictive models showed that spatial distribution of grizzly bear’s dietary niche in B.C. can be broadly categorized into coastal areas where bears are reliant on salmon, and interior areas where they are reliant on plant foods. Terrestrial meat sources and kokanee salmon provided important supplements to bear diet in certain regions, but nowhere were they as important to bear diet as plants or salmon. These results also showed that spatial variation in grizzly bear diet is not currently reflected in the boundaries of B.C.’s Grizzly Bear Population Units, which represents a major obstacle to effective management across the province.