OPP-PRF: Investigating the Effects of Late Holocene Climate Change on Polar Bears

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Polar bears evolved to thrive in the harsh Arctic environment. Because they depend on sea ice to travel and to hunt seals, past climatic changes that altered sea ice likely affected population size and distribution. This project investigates the effects of climate change – from approximately 5000 years ago to the present – on polar bears in the Bering Sea region. Polar bear remains have been identified from a 4700-year-old archaeological site on Unalaska Island, Alaska. These remains are approximately 200 miles south of where polar bears have been found in the recent past. By studying these remains, and comparing them to modern-day specimens, this research will advance understanding of the effects of historic climate cooling and present-day climate warming on polar bears. The presence of polar bear remains also has implications for the Native Unangan people. To explore the relationship between Unangan ancestors and polar bears, this project will provide training and mentorship to students and enhance the professional development of an early career Arctic scientist. Results from this study will be shared with the community in Dutch Harbor, Alaska, and through conference presentations and peer-reviewed articles.This project tests the hypothesis that late Holocene climate change resulted in demographic, genomic, and epigenomic changes in Bering Sea polar bears. The PI uses a multidisciplinary approach, combining zooarchaeological, paleogenomic and paleoepigenetic data from Neoglacial bear remains excavated from an archaeological site on Unalaska Island. First, morphometric and genomic DNA sequence data will be used to confirm that the remains are from polar bears and to determine the number of individuals represented in the assemblage. Then, genomic and epigenomic data from the Unalaskan bears will be compared to data from modern-day Bering Sea polar bears and brown bears from the Alaska Peninsula to determine 1) if polar bears and brown bears interbred in the Neoglacial Period, and 2) to assess demographic and adaptive responses of polar bear populations to Neoglacial cooling and present-day climate warming.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.