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The Population Dynamics of Polar Bears in Western Hudson Bay

  • Andrew E. Derocher
  • Ian Stirling

Abstract

Reproductive output of polar bears in western Hudson Bay declined through the 1980’s from higher levels in the 1960’s and 1970’s. Age of first reproduction increased slightly and the rate of litter production declined from 0.45 to 0.35 litters/female/year over the study, indicating that the reproductive interval had increased. Recruitment of cubs to autumn decreased from 0.71 to 0.53 cubs/female/year. Cub mortality increased from the early to late 1980’s. Litter size did not show any significant trend or significant annual variation due to an increase in loss of the whole litter. Mean body weights of females with cubs in the spring and autumn declined significantly. Weights of cubs in the spring did not decline, although weights of both female and male cubs declined over the study. The population is approximately 60% female, possibly due to the sex-biased harvest. Although estimates of population size are not available from the whole period over which we have weight and reproductive data, the changes in reproduction, weight, and cub mortality are consistent with the predictions of a densitydependent response to increasing population size.

Keywords

Litter Size Polar Bear Ringed Seal Black Bear Grizzly Bear 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Elsevier Science Publishers Ltd 1992

Authors and Affiliations

  • Andrew E. Derocher
    • 1
  • Ian Stirling
    • 2
  1. 1.Department of ZoologyUniversity of AlbertaEdmontonCanada
  2. 2.Canadian Wildlife ServiceEdmontonCanada

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