Changes in Land Distribution of Polar Bears in Western Hudson Bay


  • Lindsay Towns
  • Andrew E. Derocher
  • Ian Stirling
  • Nick J. Lunn



polar bear, Ursus maritimus, western Hudson Bay, distribution, population structure, sea-ice breakup, temporal trends


We examined the capture locations of polar bears (Ursus maritimus) on land in western Hudson Bay over 19 years (1986–2004) to assess temporal trends in the distribution of the population. We found that the distribution of bears of most age and sex groups shifted northward and eastward over the study. The causes of these shifts may be related to an altered population structure, changing environmental conditions, or a combination of both factors. Segregation by age, sex, and reproductive status persisted over time as found in earlier studies, but more females with young were within 5 km of the coast after 2001 than before. The distribution changes were correlated with the timing of sea-ice breakup, which now occurs, on average, about three weeks earlier than it did 30 years ago. While environmental conditions may have influenced polar bear distribution, the reduction in the number of large adult males along the coast may also have affected distribution patterns, allowing adult females to remain closer to the coast in more recent times.