Foraging Patterns of Polar Bears (Ursus Maritimus) in a Rapidly Changing Arctic: Insights from Harvest-Based Sampling in Nunavut, Canada

Arctic species are adapted to the seasonal changes in habitat conditions and resource availability; however, anthropogenic climate warming and associated sea ice loss are having widespread ecological consequences. Polar bears (Ursus maritimus) are top predators across their circumpolar range, where they rely on predictable sea ice patterns for life history characteristics. Thus, polar bears may be sensitive indicators of environmental change and their dietary patterns may reflect prey availability. Continued changes in environmental conditions are predicted to reduce foraging opportunities, however the mechanistic relationship between bear demography and habitat change are poorly understood. The objective of this dissertation was to identify patterns of polar bear diet composition and foraging success and examine how polar bears are responding to shifting environmental conditions in the Canadian Arctic. To examine the foraging ecology of polar bears, I used adipose tissue samples from harvested and remote biopsied bears across Nunavut, Canada from 2010-2018 with additional samples from 1999-2003 for the Foxe Basin subpopulation. I used quantitative fatty acid signature analysis to estimate diet composition and the relative lipid content of adipose tissue was used as an index of body condition. I found that seasonal fluctuations in the body condition of polar bears was correlated with seasonal changes in sea ice conditions. Polar bear diet composition varied spatially and temporally based on local prey availability. In some cases, the dietary proportion, and frequency of prey occurrence in diets was influenced by sea ice conditions that promote prey susceptibility to predation or an increase in the availability of supplemental food (i.e., marine mammal carcasses). Age- and sex-specific variation in diet was associated with the broader dietary niche of adult male bears. This dissertation provides a more comprehensive understanding of the mechanisms affecting the responses and resilience of polar bears to climate-driven environmental change. Adipose tissue samples collected during subsistence harvests of polar bears have provided unprecedented insight into the foraging ecology of polar bears. Continued monitoring of polar bear body condition and diet will help inform effective management and conservation action.