![]() Over the past 25 years, the summer sea ice melt period has lengthened, and summer sea ice cover has declined by over half a million square miles. Polar bears are not aquatic, however, and their only access to the seals is from the surface of the sea ice. Polar bears almost exclusively eat seals, and they are equally as dependent upon the sea for their nutrition as are seals, whales, and other aquatic mammals. Most important of these is foraging, or access to food. Polar bears are tied to the sea ice for nearly all of their life cycle functions. Distribution and MovementsĪ polar bear walks across rubble ice in the Alaska portion of the southern Beaufort Sea. (Credit: Mike Lockhart, USGS. Additionally, this work will allow us to develop an understanding of how polar bear populations will respond to a variety of stressors modulated by climate change, including contaminant and pathogen exposures, changes in food web structure and prey accessibility, and changes in spatial distribution. Research in this focal area is centered on (i) collecting data on a variety of systems that help determine and mediate polar bear health and energetics, and (ii) developing monitoring and surveillance programs for detecting changes in population health over time. Because of this, measuring changes in health and energetics has potential for revealing important associations between environmental stressors and population dynamics. An animal’s health and energetic state reflects the interaction between its behavioral choices and the environment. The warming climate has the potential to drive significant changes in the health and energetics of Arctic fauna, particularly those dependent on sea ice habitats like polar bears. Results of past studies have allowed us to assess the relationships between population vital rates and environmental change, which provides our partners with information needed to inform management decisions. We are currently developing an analytical approach that will allow us to integrate additional types of data (e.g., spatial data, non-invasively collected genetic data) into the modeling process to provide improved assessments of population status. To estimate both the population size and vital rates, we have used mark-recapture studies relying on physical capture of bears, primarily during the spring. In addition, the USGS collaborates with the US Fish and Wildlife Service in population studies in the Chukchi Sea. Information on the status and trends of polar bear populations are needed to inform management of polar bears under US laws and international agreements. The USGS maintains a long-term research program focused on the population dynamics of the southern Beaufort Sea polar bear population. ![]() Polar bear family at a whale bone pile near Kaktovik, Alaska.(Public domain.)
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