Drivers and consequences of individual specialization in an Arctic marine top predator

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Ongoing climate warming is affecting ecosystems worldwide. In the Arctic, where warming is occurring 2-3 times faster than the rest of the planet, ice-associated species have been acutely affected by declining sea ice area and extent. The future ecological consequences of Arctic climate warming are difficult to predict, at least partly because the mechanistic relationships between climate, habitat, and population demography are often poorly understood. To date, most ecological studies have considered animal populations as comprised of ecologically equivalent individuals. However, an emerging literature is demonstrating that individual specialization, whereby an individual uses a subset of resources available to the population as a whole, is an important driver of ecological processes and evolutionary adaptation. My proposed research involves testing hypotheses around the environmental drivers and ecological consequences of individual specialization, using the polar bear (Ursus maritimus) as a model species and target for conservation. As a long-lived top predator in a dynamic habitat, polar bears demonstrate several characteristics that promote individual specialization: interspecific competition is low, intraspecific competition may be strong, and individual foraging behaviour is highly variable. As a species that relies on the annual sea ice as its primary habitat, the polar bear is also vulnerable to demographic decline attributable to climatic warming. Past research from my lab has found that polar bear diets vary by region, age, and sex, and that foraging is affected by prey availability and sea ice conditions. We have developed and applied a suite of methods for measuring body condition and foraging success. Using biochemical methods that track the transfer of dietary components from prey to predators, we will estimate the diet composition of more than 5,000 polar bears sampled over a 20-year span. Samples come from long-term field studies in Hudson Bay and harvest-based sampling across Nunavut, both efforts ongoing since the early 2000s. Data on bear age, sex, body size, and genetic relatedness will allow us to test hypotheses about the intrinsic biological drivers of dietary specialization. We will test how specialization impacts nutritional condition and reproductive success and whether patterns of specialization are transmitted socially. We will examine the effects of sea ice conditions and prey availability and test the hypothesis that killer whales (Orcinus orca) migrating into the Arctic have indirectly affected polar bear foraging. We will use tracking collars to test for specialization in the way polar bears move and use their habitat. By identifying the factors contributing to individual fitness in an Arctic top predator, this innovative research will lead to advancement in animal ecology and inform policy and action aimed at the conservation of polar bears, a species of significant cultural and economic importance in Canada.