Journal
ECOLOGICAL APPLICATIONS
Volume 25, Issue 3, Pages 634-651Publisher
WILEY
DOI: 10.1890/14-1129.1
Keywords
abundance; Arctic; climate warming; Cormack-Jolly-Seber; demographic modeling; Horvitz-Thompson; mark-recapture; sea ice; survival; Ursus maritimus
Categories
Funding
- U.S. Geological Survey
- Ecosystems and Climate and Land Use Change Mission Areas
- U.S. Bureau of Land Management
- Canadian Wildlife Federation
- Environment Canada
- Circumpolar/Boreal Alberta Research
- Inuvialuit Game Council
- National Fish and Wildlife Federation
- Natural Sciences and Engineering Research Council of Canada
- Northern Scientific Training Program
- Northwest Territories Department of Environment and Natural Resources
- Parks Canada
- Polar Bears International
- Polar Continental Shelf Project
- Quark Expeditions
- U.S. Bureau of Ocean Energy Management
- Ecosystems Mission Area
- Science Support Partnership Program
- University of Alberta
- World Wildlife Fund (Canada)
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In the southern Beaufort Sea of the United States and Canada, prior investigations have linked declines in summer sea ice to reduced physical condition, growth, and survival of polar bears (Ursus maritimus). Combined with projections of population decline due to continued climate warming and the ensuing loss of sea ice habitat, those findings contributed to the 2008 decision to list the species as threatened under the U.S. Endangered Species Act. Here, we used mark-recapture models to investigate the population dynamics of polar bears in the southern Beaufort Sea from 2001 to 2010, years during which the spatial and temporal extent of summer sea ice generally declined. Low survival from 2004 through 2006 led to a 25-50% decline in abundance. We hypothesize that low survival during this period resulted from (1) unfavorable ice conditions that limited access to prey during multiple seasons; and possibly, (2) low prey abundance. For reasons that are not clear, survival of adults and cubs began to improve in 2007 and abundance was comparatively stable from 2008 to 2010, with; similar to 900 bears in 2010 (90% CI 606-1212). However, survival of subadult bears declined throughout the entire period. Reduced spatial and temporal availability of sea ice is expected to increasingly force population dynamics of polar bears as the climate continues to warm. However, in the short term, our findings suggest that factors other than sea ice can influence survival. A refined understanding of the ecological mechanisms underlying polar bear population dynamics is necessary to improve projections of their future status and facilitate development of management strategies.
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