Climate change consequences for an Arctic apex predator: polar bears as ecological indicators

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Predicting the impacts of environmental change on species requires an understanding of biological processes such as reproduction, survival, growth, behaviour, habitat use, foraging, migration, and timing of life history events. The main objective of this project is to identify the mechanisms associated with polar bear (Ursus maritimus) population change over time by documenting past dynamics to allow predictions of future change relative to climate change and altered sea ice conditions. Polar bears are the apex predator in the Arctic marine ecosystem and development of early warning indicators are essential for effective conservation and management. The research uses three integrated methodologies including satellite telemetry, analysis of tissues that record life history or physiological status, and mathematical modelling. The project builds on long-term polar bear population studies in Western Hudson Bay and the Beaufort Sea. This project focuses on four themes: 1) the spatial ecology and habitat use of polar bears using remote sensing to assess temporal aspects relevant to key life history parameters, 2) development of interdisciplinary means of assessing life history events from microanalysis of tissues, 3) exploration of ecosystem dynamics and energetics modelling to predict the future status of polar bears, and 4) examine the role of polar bears as a keystone predator in Arctic marine ecosystems. Satellite telemetry data will be used to develop regional sea ice models to predict future conditions relevant to polar bears with focus on key periods that affect reproduction and survival. Integration of these data into mathematical models (e.g., dynamic energy budget models, population projection models, and ecosystem models) allows an improved understanding of population dynamics. Coincident field sampling of tissues that record life history (e.g., tooth annuli, claw shavings, hair, fat, and blood) are being used to develop new cross-disciplinary insights into polar bear ecology. Tissue archives will be used to examine how changes in sea ice regimes are associated with nutritional stress in polar bears (e.g., cortisol levels in hair) while distribution, diet, and migration patterns will be examined using isotopic signatures and fatty acid profiles. The results will specifically address how climate change affects foraging success and movement patterns of polar bears, and thus may provide a mechanistic understanding of the decline in polar bear body condition associated with demographics. The goal is to use these archives to glean new and important information about stressor responses over time to develop early warning indicators. Overall, this project will serve to introduce novel interdisciplinary techniques with remote sensing approaches integrated with projection models.