Abundance estimate of 1000 (95% CI: 715-1398) from 2011, few observations of females with cubs. Declines in survival and birth rates and body condition have been linked to earlier ice-break up.
Status table outtake
Status and delineation
The current population boundaries of the Western Hudson Bay (WH) subpopulation are based on extensive records of capture, recapture, and harvest of tagged animals (Stirling et al. 1977, Derocher and Stirling 1990, 1995, Taylor and Lee 1995, Lunn et al. 1997). This subpopulation appears to be geographically segregated from the Southern Hudson Bay subpopulation to the southeast and the Foxe Basin subpopulation to the north during the open-water season, although all three subpopulations mix on the Hudson Bay sea ice during the winter and spring (Stirling et al. 1977, Derocher and Stirling 1990, Stirling and Derocher1993, Taylor and Lee 1995).
During the 1960s and 70s, subpopulation abundance likely increased with the closure of the fur trading post at York Factory, withdrawal of military personnel from Churchill, and the closure of hunting in Manitoba (Stirling et al. 1977, Derocher and Stirling 1995). Derocher and Stirling (1995) estimated the mean population size for 1978-1992 to be 1000 ± 51. This estimate was considered conservative because the study had not covered the southern portion of the range east of the Nelson River; for management purposes, population size was adjusted to 1200 (Calvert et al. 1995, Wiig et al. 1995). In 1994 and 1995, Lunn et al. (1997) expanded the capture program to sample animals to the boundary between WH and SH. Using these additional data, they estimated the abundance to be 1233 ± 209 in 1995. Regehr et al. (2007) reported a decline in abundance from 1194 (95% CI = 1020, 1368) in 1987 to 935 (95% CI = 794, 1076) in 2004. Further, the survival rates of cubs, sub-adults, and old bears (>20 years) were negatively correlated with the date of sea ice breakup (Regehr et al. 2007).
A comprehensive aerial survey was conducted in 2011 as part of a program by the Government of Nunavut to continue development of non-invasive techniques to estimate abundance and to address inconsistencies between local knowledge and perceptions that suggest WH is increasing and the research that suggest WH is decreasing (Stapleton et al. 2014). Both distance sampling and sight-resight protocols were used on the survey; a total of 711 bears were sighted. Analysis of the survey data resulted in an abundance estimate of 1,030 (95% CI = 754, 1406). More bears, particularly adult males, were observed in the coastal areas east of the Nelson River towards the WH/SH boundary than were documented during the late 1990s (Stirling et al. 2004). Stapleton et al. (2014) suggested that a distributional shift may have negatively biased abundance estimates derived from capture samples. However, in the two years following that of the aerial survey, far fewer bears were seen in the area east of the Nelson River at the same time of year (unpublished data). As well, the mean litter size (cubs-of-the-year, 1.43±0.08; yearlings, 1.22±0.10) and number of cubs observed as a proportion of total observations (cubs-of-the-year, 0.07; yearlings, 0.03) were lower than those recorded for the neighboring subpopulations of Foxe Basin and Southern Hudson Bay and consistent with WH having low reproductive productivity (Regehr et al. 2007, Peacock et al. 2010, Stapleton et al. 2014). The body mass of solitary adult female polar bears has declined over the past 30 years, which has likely contributed to declining reproductive success.
Lunn et al. (2014) evaluated the demography and population status of WH for the period 1984-2011, using a Bayesian implementation of multistate capture-recapture models, coupled with a matrix-based demographic projection model, to integrate several types of data and to incorporate sampling uncertainty, and demographic and environmental stochasticity across the polar bear life cycle. Their analysis resulted in an estimate of 806 (95% CI = 653,984) for polar bears in the core area of study north of the Nelson River in 2011. Although both the aerial survey and capture-recapture estimates are broadly similar with overlapping confidence intervals, it is difficult to make direct comparisons because different methods were used and the geographical area covered differed. The aerial survey likely provides an accurate “snapshot” estimate of the total number and distribution of polar bears in the WH management area at the time of the survey. The point estimate of abundance from the capture-recapture model, represents the number of bears that move through the capture-recapture sampling area.
In addition to an estimate of abundance, Lunn et al. (2014) documented a significant relationship between sea ice conditions and survival of female polar bears of all age classes. For the recent decade 2001-2011, the growth rate of the female segment of the population was 1.02 (95% CI = 0.98, 1.06), which may be due in large part to nonlinearity (i.e., short-term stability) in the long-term observed and forecasted trend toward earlier sea ice break-up in western Hudson Bay.
Atkinson, S., D. Garshelis, S. Stapleton, and D. Hedman. 2012. Western Hudson Bay polar bear aerial survey, 2011. Unpublished final report, Government of Nunavut, 57 pages.
Calvert, W., M. Taylor, I. Stirling, G. B. Kolenosky, S. Kearney, M. Crête, and S. Luttich. 1995. Polar bear management in Canada 1988-92. Pp. 61-79 in Ø. Wiig, E. W. Born, and G. W. Garner, eds. Polar Bears: Proceedings of the Eleventh Working Meeting of the IUCN/SSC Polar Bear Specialist Group. IUCN, Gland, Switzerland and Cambridge, UK.
Cherry, S. G., A. E. Derocher, G. W. Thiemann, and N. J. Lunn. 2013. Migration phenology and seasonal fidelity of an Arctic marine predator in relation to sea ice dynamics. Journal of Animal Ecology 82:912-921.
Derocher, 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.
Derocher, A. E., and I. Stirling. 1995. Estimation of polar bear population size and survival in western Hudson Bay. Journal of Wildlife Management 59:215-221.
Derocher, A. E., I. Stirling, and W. Calvert. 1997. Male-biased harvesting of polar bears in western Hudson Bay. Journal of Wildlife Management 61:1075-1082.
Derocher et al. 2004.
Dyck, M. G., and R. K. Baydack. 2004. Vigilance behaviour of polar bears (Ursus maritimus) in the context of wildlife-viewing activities at Churchill, Manitoba, Canada. Biological Conservation 116:343-350.
Gagnon, A. S., and W. A. Gough. 2005. Trends in dates of ice freeze-up and break-up over Hudson Bay, Canada. Arctic 58:370-382.
Hochheim, K., D. G. Barber, and J. V. Lukovich. 2010. Changing sea ice conditions in Hudson Bay, 1980-2005. Pp. 39-51 in S. H. Ferguson, L. L. Loseto, and M. L. Mallory, eds. A Little Less Arctic: Top Predators in the World’s Largest Northern Inland Sea. Springer, New York.
Kearney, S. R. 1989. The Polar Bear Alert Program at Churchill, Manitoba. Pp. 83-92 in M. Bromley, ed. Bear-People Conflicts: Proceedings of a Symposium on Management Strategies. Northwest Territories Department of Renewable Resources, Yellowknife.
Lie, E., H. J. S. Larsen, S. Larsen, G. M. Johansen, A. E. Derocher, N. J. Lunn, R. J. Norstrom, Ø. Wiig, and J. U. Skaare. 2004. Does high organochlorine (OC) exposure impair the resistance to infection in polar bears (Ursus maritimus)? Part I: Effect of OCs on the humoral immunity. Journal of Toxicology and Environmental Health, Part A 67:555-582.
Lie, E., H. J. S. Larsen, S. Larsen, G. M. Johansen, A. E. Derocher, N. J. Lunn, R. J. Norstrom, Ø. Wiig, and J. U. Skaare. 2005. Does high organochlorine (OC) exposure impair the resistance to infection in polar bears (Ursus maritimus)? Part II: Possible effect of OCs on mitogen- and antigen-induced lymphocyte proliferation. Journal of Toxicology and Environmental Health, Part A 68:457-484.
Lemelin, R. H. 2005. Wildlife tourism at the edge of chaos: Complex interactions between humans and polar bears in Churchill, Manitoba. Pp.183-202 in F. Berkes, R. Huebert, H. Fast, M. Manseau, and A. Diduck, eds. Breaking Ice: Renewable Resource and Ocean Management in the Canadian North. University of Calgary Press, Calgary, AB.
Lunn NJ, Servanty S, Regehr EV, Converse SJ, Richardson E, and Stirling I. 2014. Demography and population status of polar bears in Western Hudson Bay, Canada. Environment Canada Research Report.
Lunn, N. J., M. Branigan, L. Carpenter, J. Justus, D. Hedman, D. Larsen, S. Lefort, R. Maraj, M. E. Obbard, E. Peacock, and F. Pokiak, F. 2010. Polar bear management in Canada, 2005-2008. Pp. 87-113 in M. E. Obbard, G. W. Thiemann, E. Peacock, and T. D. DeBruyn, eds. Polar Bears: Proceedings of the Fifteenth Working Meeting of the IUCN/SSC Polar Bear Specialist Group. IUCN, Gland, Switzerland and Cambridge, UK.
Lunn, N. J., I. Stirling, D. Andriashek, and G. B. Kolenosky. 1997. Re-estimating the size of the polar bear population in Western Hudson Bay. Arctic 50:234-240.
McDonald, M., L. Arragutainaq, and Z. Novalinga. 1997. Voices from the Bay: Traditional Knowledge of Inuit and Cree in the Hudson Bay Bioregion. Canadian Arctic Resources Committee, Ottawa and Environmental Committee of Municipality of Sanikiluaq, Sanikiluaq, 98 pages.
McKinney, M. A., R. J. Letcher, J. Aars, E. W. Born, M. Branigan, R. Dietz, T. J. Evans, G. W. Gabrielsen, E. Peacock, and C. Sonne. 2011. Flame retardants and legacy contaminants in polar bears from Alaska, Canada, East Greenland and Svalbard, 2005-2008. Environment International 37:365–374.
McKinney, M. A., E. Peacock, and R. J. Letcher. 2009. Sea ice-associated diet change increases the level of chlorinated and bromiated contaminants in polar bears. Environmental Science & Technology 43:4334-4339.
McKinney, M. A., I. Stirling, N. J. Lunn, E. Peacock, and R. J. Letcher 2010. The role of diet on long-term concentration and pattern trends of brominated and chlorinated contaminants in western Hudson Bay polar bears, 1991-2007. Science of the Total Environment 408:6210–6222.
Molnár, P. K., A. E. Derocher, T. Klanjscek, and M. A. Lewis. 2011. Predicting climate change impacts on polar bear litter size. Nature Communications 2:186, DOI: 10.1038/ncomms1183.
Molnár, P. K., A. E. Derocher, G. W. Thiemann, and M. A. Lewis. 2010. Predicting survival, reproduction and abundance of polar bears under climate change. Biological Conservation 143:1612-1622.
Muir, D. C. G., S. Backus, A. E. Derocher, R. Dietz, T. J. Evans, G. W. Gabrielsen, J. Nagy, R. J. Norstrom, C. Sonne, I. Stirling, M. K. Taylor, and R. J. Letcher. 2006. Brominated flame retardants in polar bears (Ursus maritimus) from Alaska, the Canadian Arctic, East Greenland, and Svalbard. Environmental Science & Technology 40:449-455.
Nirlungayuk, G., and D. S. Lee. 2009. A Nunavut Inuit perspective on Western Hudson Bay polar bear management and the consequences for conservation hunting. Pp. 135-142 in M. M. R. Freeman, and L. Foote, eds. Inuit, Polar Bears, and Sustainable Use: Local, National and International Perspectives. CCI Press, University of Alberta, Edmonton.
Norstrom, R. J., S. E. Belikov, E.W. Born, G.W. Garner, B. Malone, S. Olpinski, M. A. Ramsay, S. Schliebe, I. Stirling, M. S. Stishov, M. K. Taylor, and Ø.Wiig. 1998. Chlorinated hydrocarbon contaminants in polar bears from Eastern Russia, North America, Greenland, and Svalbard: biomonitoring of arctic pollution. Archives of Environmental Contamination and Toxicology 35:354–367.
Peacock, E., A. E. Derocher, N. J. Lunn, and M. E. Obbard. 2010. Polar bear ecology and management in Hudson Bay in the face of climate change. Pp. 93-115 in S. H. Ferguson, L. L. Loseto, and M. L. Mallory, eds. A Little Less Arctic: Top Predators in the World’s Largest Northern Inland Sea. Springer, New York.
Peacock, E., and M. K. Taylor. 2007. Polar bears of western Hudson Bay: survey extension investigation. Government of Nunauvt unpublished report, 16 pages.
Regehr, E. V., N. J. Lunn, S. C. Amstrup, and I. Stirling. 2007. Effects of earlier sea ice breakup on survival and populaiton size of polar bears in western Hudson Bay. Journal of Wildlife Management 71:2673 - 2683.
Stapleton S, Atkinson S, Hedman D, and Garshelis D. 2014. Revisiting Western Hudson Bay: using aerial surveys to update polar bear abundance in a sentinel population. Biological Conservation 170:38-47.
Stewart, E. J., S. E. L. Howell, D. Draper, J. Yackel, and A. Tivy. 2007. Sea ice in Canada’s arctic: implications for cruise tourism. Arctic 60:370-380.
Stewart, E. J., A. Tivy, S. E. L. Howell, J. Dawson, and D. Draper. 2010. Cruise tourism and sea ice in Canada’s Hudson Bay region. Arctic 63:57-66.
Stirling, I., and A. E. Derocher. 1993. Possible impacts of climatic warming on polar bears. Arctic 46:240-245.
Stirling, I., A. E. Derocher, W. A. Gough, and K. Rode. 2008. Response to Dyck et al. (2007) on polar bears and climate change in western Hudson Bay. Ecological Complexity 5:193-201.
Stirling, I., C. Jonkel, P. Smith, R. Robertson, and D. Cross. 1977. The ecology of the polar bear (Ursus maritimus) along the western coast of Hudson Bay. Canadian Wildlife Service Occasional Paper 33, 64 pages.
Stirling, I., N. J. Lunn, and J. Iacozza. 1999. Long-term trends in the population ecology of polar bears in western Hudson Bay in relation to climatic change. Arctic 52:294-306.
Stirling, I., N. J. Lunn, J. Iacozza, C. Elliott, and M. Obbard. 2004. Polar bear distribution and abundance on the Southwestern Hudson Bay Coast during open water season, in relation to population trends and annual ice patterns. Arctic 57:15-26.
Taylor, M., and J. Lee. 1995. Distribution and abundance of Canadian polar bear populations - a management perspective. Arctic 48:147-154.
Tyrrell, M. 2006. More bears, less bears: Inuit and scientific perceptions of polar bear populations on the west coast of Hudson Bay. Journal of Inuit Studies 30:191-208.
Tyrrell, M. 2009. West Hudson Bay polar bears: the Inuit perspective. Pp. 95-110 in M. M. R. Freeman, and L. Foote, eds. Inuit, Polar Bears, and Sustainable Use: Local, National and International Perspectives. CCI Press, University of Alberta, Edmonton.
Verreault, J., D. C. G. Muir, R. J. Norstrom, I. Stirling, A. T. Fisk, G. W. Gabrielsen, A. E. Derocher, T. J. Evans, R. Dietz, C. Sonne, G. M. Sandala, W. Gebbink, F. F. Riget, E. W. Born, M. K. Taylor, J. Nagy, and R. J. Letcher. 2005. Chlorinated hydrocarbon contaminants and metabolites in polar bears (Ursus maritimus) from Alaska, Canada, East Greenland, and Svalbard: 1996-2002. Science of the Total Environment 351–352:369–390.
Wiig, Ø., E. W. Born, and G. W. Garner, eds. 1995. Polar Bears: Proceedings of the Eleventh Working Meeting of the IUCN/SSC Polar Bear Specialist Group. IUCN, Gland, Switzerland and Cambridge, UK.