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Observations of mortality associated with extended open-water swimming by polar bears in the Alaskan Beaufort Sea

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Abstract

During aerial surveys in September 1987–2003, a total of 315 live polar bears were observed with 12 (3.8%) animals in open water, defined for purposes of this analysis as marine waters >2 km north of the Alaska Beaufort Sea coastline or associated barrier islands. No polar bear carcasses were observed. During aerial surveys in early September, 2004, 55 polar bears (Ursus maritimus) were seen, 51 were alive and of those 10 (19.9%) were in open water. In addition, four polar bear carcasses were seen floating in open water and had, presumably, drowned. Average distance from land and pack ice edge for live polar bears swimming in open water in 2004 (n=10) were 8.3±3.0 and 177.4±5.1 km, respectively. We speculate that mortalities due to offshore swimming during late-ice (or mild ice) years may be an important and unaccounted source of natural mortality given energetic demands placed on individual bears engaged in long-distance swimming. We further suggest that drowning-related deaths of polar bears may increase in the future if the observed trend of regression of pack ice and/or longer open water periods continues.

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Acknowledgements

We thank Steve Treacy who was research manager for most of the project’s duration (1987–2003). We thank Cleve Cowles who has been project supervisor since its inception. We thank the numerous personnel from the Minerals Management Service and other agencies who participated in BWASP as team leaders, observers, data recorders or in other capacities during this project. We greatly appreciate the services, knowledge and skills provided by staff, and pilots of ERA, Inc. who participated in the surveys, as well as support from the Department of Interior, Office of Aircraft Services, Anchorage. Project data collection and field analysis programs used throughout were designed by John Bennett, John Dunlap and Tom Murrell. Matt Heller assisted with data management and figure preparation. Warren Horowitz managed contracts that provided weather from the Endicott Weather Station. We also acknowledge the National Ice Center for providing data on sea ice conditions. We thank Craig Perham and Susanne Miller for sharing data on observations of bears on land along the Beaufort Sea coastline. We thank Ian Stirling and Richard Shideler for sharing observations of polar bears suffering from fatigue upon coming ashore following open-water swimming. This paper benefited greatly from reviews by, and discussions with, Andrew Derocher, Lisa Rotterman, Richard Shideler, Ian Stirling and Cleveland Cowles. This paper was improved by useful comments from Rolf Gradinger and three anonymous reviewers. Funding for BWASP surveys was provided by the U.S. Minerals Management Service, Alaska Outer Continental Shelf Region. The findings and conclusions in this paper are those of the authors and do not necessarily represent the views of the funding agency. Any mention of trade names is coincidental and does not represent endorsement by the government.

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  1. Minerals Management Service, Environmental Studies Section, 3801 Centerpoint Drive, Suite 500, Anchorage, AK, 99503, USA

    Charles Monnett & Jeffrey S. Gleason

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  1. Charles Monnett
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  2. Jeffrey S. Gleason
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Correspondence to Charles Monnett.

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Monnett, C., Gleason, J.S. Observations of mortality associated with extended open-water swimming by polar bears in the Alaskan Beaufort Sea. Polar Biol 29, 681–687 (2006). https://doi.org/10.1007/s00300-005-0105-2

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  • DOI: https://doi.org/10.1007/s00300-005-0105-2

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