The Population Dynamics of Polar Bears in Western Hudson Bay

  • Andrew E. Derocher
  • Ian Stirling


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.


Litter Size Polar Bear Ringed Seal Black Bear Grizzly Bear 
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Literature Cited

  1. Amstrup, S. C, I. Stirling, and J. W. Lentfer. 1986. Past and present status of polar bears in Alaska. Wildlife Society Bulletin 14: 241–254.Google Scholar
  2. Baker, J. M., and M. V. Angel. 1987. Marine processes. Pages 50–74 in J. G. Nelson, R. Needham, and L. Norton, editors. Arctic Heritage. Association of Canadian Universities for Northern Studies, Ottawa, Ontario, Canada.Google Scholar
  3. Bunnell, F. L., and D. E. N. Tait. 1981. Population dynamics of bears — implications. Pages 75–98 in C. W. Fowler, and T. D. Smith, editors. Dynamics of large mammal populations. John Wiley and Sons, New York, New York, USA.Google Scholar
  4. DeMaster, D. P., M. C. S. Kingsley, and I. Stirling. 1980. A multiple mark and recapture estimate applied to polar bears. Canadian Journal of Zoology 58: 633–638.CrossRefGoogle Scholar
  5. DeMaster, D. P., and I. Stirling. 1981. Ursus maritimus. Mammalian Species 145: 1–7.CrossRefGoogle Scholar
  6. Derocher, A. E., R. A. Nelson, I. Stirling, and M. A. Ramsay. 1990. Effects of fasting and feeding on serum urea and serum creatinine levels in polar bears. Marine Mammal Science 6: 196–203.CrossRefGoogle Scholar
  7. Dérocher, A. E., and I. Stirling. 1990. Distribution of polar bears (Ursus maritimus) during the ice-free period in western Hudson Bay. Canadian Journal of Zoology 68: 1395–1403.CrossRefGoogle Scholar
  8. Derocher, A. E., I. Stirling, and D. Andriashek. In press. Pregnancy rates and serum progesterone levels of polar bears in western Hudson Bay. Canadian Journal of Zoology.Google Scholar
  9. Dunbar, M. J. 1970. Ecosystem adaptation in marine polar environments. Pages 105–111 in M. W. Holdgate, editor. Antarctic Ecology, Volume 1. Academic Press, London, England.Google Scholar
  10. Fowler, C. W. 1981a. Density dependence as related to life history strategy. Ecology 62: 602–610.CrossRefGoogle Scholar
  11. Fowler, C. W. 1981b. Comparative population dynamics in large mammals. Pages 437–455 in C. W. Fowler, and T. D. Smith, editors. Dynamics of large mammal populations. John Wiley and Sons, New York, New York, USA.Google Scholar
  12. Fowler, C. W. 1990. Density dependence in northern fur seals (Callorhinus ursinus). Marine Mammal Science 6: 171–196.CrossRefGoogle Scholar
  13. Hammill, M. O., and T. G. Smith. 1991. The role of predation in the ecology of the ringed seal in Barrow Strait, Northwest Territories, Canada. Marine Mammal Science 7: 123–135.CrossRefGoogle Scholar
  14. Kingsley, M. C. S. 1979. Fitting the von Bertalanffy growth equations to polar bear age-weight data. Canadian Journal of Zoology 57: 1020–1025.CrossRefGoogle Scholar
  15. Kolenosky, G. B., N. J. Lunn, C. J. Greenwood, and K. F. Abraham. 1989. Estimating the weight of polar bears from body measurements. Journal of Wildlife Management 53: 188–190.CrossRefGoogle Scholar
  16. Larsen, T. 1985. Polar bear denning and cub production in Svalbard, Norway. Journal of Wildlife Management 49: 320–326.CrossRefGoogle Scholar
  17. Larsen, T. 1986. Population biology of the polar bear (Ursus maritimus) in the Svalbard area. Norsk Polarinstitut Skrifter 184: 1–55.Google Scholar
  18. Laws, R. M. 1956. Growth and sexual maturity in aquatic mammals. Nature 178: 193–194.CrossRefGoogle Scholar
  19. Lentfer, J. W., R. J. Hensel, J. R. Gilbert, and F. E. Sorensen. 1980. Population characteristics of Alaskan polar bears. International Conference on Bear Research and Management 4: 109–115.Google Scholar
  20. Lunn, N. J., and I. Stirling. 1985. The significance of supplemental food to polar bears during the ice-free period of Hudson Bay. Canadian Journal of Zoology 63: 2291–2297.CrossRefGoogle Scholar
  21. McCullough, D. R. 1981. Population dynamics of the Yellowstone grizzly bear. Pages 173–196 in C. W. Fowler, and T. D. Smith, editors. Dynamics of large mammal populations. John Wiley and Sons, New York, New York, USA.Google Scholar
  22. Ramsay, M. A., and I. Stirling. 1988. Reproductive biology of female polar bears (Ursus maritimus). Journal of Zoology (London) 214: 601–634.CrossRefGoogle Scholar
  23. Sadleir, R. M. F. S. 1969. The ecology of reproduction in wild and domestic mammals. Methuen Press, London, England.Google Scholar
  24. Smith, T. G. 1980. Polar bear predation of ringed and bearded seals in the land-fast sea ice habitat. Canadian Journal of Zoology 58: 2201–2209.CrossRefGoogle Scholar
  25. Stirling, I., and W. R. Archibald. 1977. Aspects of predation of seals by polar bears. Journal of the Fisheries Research Board of Canada 34: 1126–1129.CrossRefGoogle Scholar
  26. Stirling, I., W. R. Archibald, and D. DeMaster. 1977a. Distribution and abundance of seals in the Beaufort Sea. Journal of the Fisheries Research Board of Canada 43: 976–988.CrossRefGoogle Scholar
  27. Stirling, I., W. Calvert, and D. Andriashek. 1980. Population ecology studies of the polar bear in the area of southeastern Baffin Island. Canadian Wildlife Service Occasional Paper 44, Ottawa, Canada.Google Scholar
  28. Stirling, I., C. Jonkel, P. Smith, R. Robertson, and D. Cross. 1977b. The ecology of the polar bear (Ursus maritimus) along the western coast of Hudson Bay. Canadian Wildlife Service Occasional Paper 33, Ottawa, Canada.Google Scholar
  29. Stirling, I., M. C. S. Kingsley, and W. Calvert. 1982. The distribution and abundance of seals in the eastern Beaufort Sea, 1974–79. Canadian Wildlife Service Occasional Paper 47, Ottawa, Canada.Google Scholar
  30. Stirling, I., A. M. Pearson, and F. L. Bunnell. 1976. Population ecology studies of polar and grizzly bears in Northern Canada. Transactions of the North American Wildlife and Natural Resources Conference 41: 421–429.Google Scholar
  31. Stirling, I., C. Spencer, and D. Andriashek. 1989. Immobilization of polar bears (Ursus maritimus) with Telazol® in the Canadian Arctic. Journal of Wildlife Diseases 25: 159–168.Google Scholar
  32. Stringham, S. F. 1983. Roles of adult males in grizzly bear population biology. International Conference on Bear Biology and Management 5: 140–151.Google Scholar
  33. Taylor, M., T. Larsen, and R. E. Schweinsburg. 1985. Observations of intraspecific aggression and cannibalism in polar bears. Arctic 38: 303–309.Google Scholar
  34. Taylor, M. K., D. P. DeMaster, F. L. Bunnell, and R. E. Schweinsburg. 1987. Modeling the sustainable harvest of female polar bears. Journal of Wildlife Management 51: 811–820.CrossRefGoogle Scholar
  35. Tietje, W. D., B. O. Pelchat, and R. L. Ruff. 1986. Cannibalism of denned black bears. Journal of Mammalogy 67: 762–766.CrossRefGoogle Scholar
  36. Watts, P. D., and S. E. Hansen. 1987. Cyclic starvation as a reproductive strategy in the polar bear. Symposium of the Zoological Society of London 57: 306–318.Google Scholar
  37. Young, B. F., and R. L. Ruff. 1982. Population dynamics and movements of black bears in east central Alberta. Journal of Wildlife Management 46: 845–860.CrossRefGoogle Scholar

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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