Abstract 205 – Using Polar Bear (Ursus maritimus) Diet Estimates to Model the Effect of Climate Change on Arctic Marine Predator Body Condition

Griffin Finkbeiner, Gregory W. Thiemann, Melissa P. Galicia, Alyssa M. Bohart

Arctic ecosystems have been disproportionately impacted by climate change, warming at a rate
four times faster than the global average. Polar bears (Ursus maritimus) rely on annual ice as a
platform to travel and hunt, and warming-driven loss of Arctic sea-ice represents a reduction in
optimal foraging area with subsequent impacts on predator-prey relationships. Phenotypic
responses to these environmental changes (i.e., phenotypic plasticity) may involve shifts in
foraging strategy, including the degree of specialization an individual may demonstrate. Dietary
specialization, where an individual demonstrates a narrower or altered foraging niche
compared to the overall population, is the response of an individual altering foraging behaviour
to maximize energy intake. The objective of this research is to develop a model for
understanding the drivers and consequences of dietary specialization on Arctic marine
predators in a warming climate. Using harvest-based sampling of two adjacent polar bear
subpopulations—Foxe Basin and Davis Strait—we will study the effect of long-term climate
warming on polar bear diet (composition and diversity) and body condition. Diet estimates will
be created using quantitative fatty acid signature analysis (QFASA), with adipose tissue lipid
content and subjective fatness index (SFI) scores being used as body condition indicators. We
hypothesized that environmental changes, including declining sea-ice levels, have promoted
sex-specific responses in adult polar bears, with increased specialization among males, where
females with better body condition will show a more generalized diet. The outcomes of this
research will provide valuable insights into the ecological impacts of climate warming on Arctic
marine predators, informing future conservation and management strategies. Moreover,
changes in polar bear diet specialization may serve as an indicator of food web connectivity and
health in the rapidly changing Arctic environment.