Polar bears (Ursus maritimus) prefer to live on Arctic sea ice but may swim between ice floes or between sea ice and land. Although anecdotal observations suggest that polar bears are capable of swimming long distances, no data have been available to describe in detail long distance swimming events or the physiological and reproductive consequences of such behavior. Between an initial capture in late August and a recapture in late October 2008, a radio-collared adult female polar bear in the Beaufort Sea made a continuous swim of 687 km over 9 days and then intermittently swam and walked on the sea ice surface an additional 1,800 km. Measures of movement rate, hourly activity, and subcutaneous and external temperature revealed distinct profiles of swimming and walking. Between captures, this polar bear lost 22% of her body mass and her yearling cub. The extraordinary long distance swimming ability of polar bears, which we confirm here, may help them cope with reduced Arctic sea ice. Our observation, however, indicates that long distance swimming in Arctic waters, and travel over deep water pack ice, may result in high energetic costs and compromise reproductive fitness.
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Primary funding for this research was provided through a National Science Foundation grant (OPP 0732713) to the University of Wyoming. Major funding also was provided by the United States Geological Survey, Climate and Land Use Change Research and Development Program, and the United States Fish and Wildlife Service, Region 7 Marine Mammals Management program. Polar bear captures are made possible under U.S. Fish and Wildlife marine mammal research permit 690038 granted to the USGS, Alaska Science Center. Capture procedures were conducted under the approval of both University of Wyoming and Alaska Science Center Institutional Animal Care and Use Committee (IACUC) protocols. We thank David Douglas (USGS) for assistance in analysis of Argos data and Ignatius Rigor (University of Washington) for providing buoy location data. The following individuals are acknowledged for their constructive suggestions on earlier versions of this report: Layne Adams, Andrew Derocher, Karen Oakley, Ignatius Rigor, Joel Schmutz, and one anonymous reviewer. Any mention of trade names is for descriptive purposes only and does not reflect endorsement by the U.S. government.
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Durner, G.M., Whiteman, J.P., Harlow, H.J. et al. Consequences of long-distance swimming and travel over deep-water pack ice for a female polar bear during a year of extreme sea ice retreat. Polar Biol 34, 975–984 (2011). https://doi.org/10.1007/s00300-010-0953-2
- Climate change
- Long-distance swimming
- Polar bear
- Ursus maritimus
- Sea ice