Abstract
Intraspecific killing has been reported among polar bears (Ursus maritimus), brown bears (U. arctos), and black bears (U. americanus). Although cannibalism is one motivation for such killings, the ecological factors mediating such events are poorly understood. Between 24 January and 10 April 2004, we confirmed three instances of intraspecific predation and cannibalism in the Beaufort Sea. One of these, the first of this type ever reported for polar bears, was a parturient female killed at her maternal den. The predating bear was hunting in a known maternal denning area and apparently discovered the den by scent. A second predation event involved an adult female and cub recently emerged from their den, and the third involved a yearling male. During 24 years of research on polar bears in the southern Beaufort Sea region of northern Alaska and 34 years in northwestern Canada, we have not seen other incidents of polar bears stalking, killing, and eating other polar bears. We hypothesize that nutritional stresses related to the longer ice-free seasons that have occurred in the Beaufort Sea in recent years may have led to the cannibalism incidents we observed in 2004.
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Acknowledgements
We thank T. Evans, G. York, J. Wilder and S. Partridge for assistance in Alaska. We also thank T. DeGange and S. Schliebe for valuable comments and guidance regarding this manuscript. The ExxonMobil Production Company, Inc. funded the infrared helicopter survey during which the dead denning female was discovered. Other funding was provided jointly by the US Geological Survey and the US Fish and Wildlife Service, and BP Exploration Alaska, Inc., Conoco-Phillips Alaska, Inc. National Fish and Wildlife Foundation, Government of the Northwest Territories (Department of Resources, Wildlife, and Economic Development), Polar Continental Shelf Project, and the Canadian Wildlife Service. We thank Dennis Andriashek for determining the ages of untagged bears and Corey Davis for determining the sex of the yearling.
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Amstrup, S.C., Stirling, I., Smith, T.S. et al. Recent observations of intraspecific predation and cannibalism among polar bears in the southern Beaufort Sea. Polar Biol 29, 997–1002 (2006). https://doi.org/10.1007/s00300-006-0142-5
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DOI: https://doi.org/10.1007/s00300-006-0142-5