Southern Hudson Bay (SH)

A recent estimate produced by means of distance sampling is 780 bears (2016). Body condition of bears has declined since the 1980s.

Status table outtake

Size Sea ice metrics Human-caused removals 2010–2014
Estimate /
95% CI
Year Method Change in spring ice retreat / Change in fall ice advance (days per decade) Change in summer sea ice area (percent change per decade) 5-yr mean Last year
Potential Actual Potential Actual
780
590-1029
2016Distance sampling-3.1/4.1-11.460.258.84543
See also the complete table (all subpopulations)

Comments, vulnerabilities and concerns

Declining body condition, declining survival rates.

Status and delineation

Southern Hudson Bay subpopulation mapThe Southern Hudson Bay area. See also the complete map (all subpopulations).

Boundaries of the Southern Hudson Bay polar bear subpopulation are based on observed movements of marked and collared bears (Jonkel et al. 1976, Kolenosky and Prevett 1983, Kolenosky et al. 1992, Obbard and Middel 2012, Middel 2013). The range of the SH subpopulation includes much of eastern and southern Hudson Bay and James Bay and large expanses of the coastline of Ontario and Québec as well as areas up to 120 km inland (Kolenosky and Prevett 1983, Obbard and Walton 2004, Obbard and Middel 2012).
 
An initial estimate of population size of 763 ± 323 animals was derived through a 3-year (1984–1986) capture-recapture study conducted in mainland Ontario (Kolenosky et al. 1992). This estimate was subsequently adjusted to 1000 for management purposes by the Canadian Polar Bear Technical Committee (PBTC) because areas away from the coast may have been under-sampled due to the difficulty of locating polar bears in the boreal forest and some areas in James Bay were not sampled (Lunn et al. 1998). A re-analysis of the 1984-1986 capture data produced an estimate for the study area of 641 (95% CI = 401–881 for those years (Obbard 2008, Obbard et al. 2007). A subsequent 3-year capture-recapture study (2003-05) produced an estimate of 673 (95% CI 396-950; Obbard 2008). An analysis of bears captured on Akimiski Island in James Bay during 1997 and 1998 resulted in the addition of 70–110 bears to the total subpopulation estimate (Obbard 2008). Results of the two capture-recapture studies suggest that abundance was unchanged between 1984-86 and 2003-05, though survival rates in all age and sex categories and body condition may have declined (Obbard et al. 2006, Obbard 2008).

To update the abundance estimate, intensive aerial surveys were conducted during the fall ice-free season over mainland Ontario (same geographic area as for the capture–recapture studies) and Akimiski Island in 2011 and over the remaining islands in James Bay, the coastal areas of Québec from Long Island to the SH–FB border, and the off-shore islands in eastern Hudson Bay in 2012. Results of this mark-recapture-distance-sampling (MRDS) analysis provided an estimate of 860 bears (95% CI: 580–1,274) in the mainland Ontario, neighboring islands, and Akimiski Island portions of the SH management unit during the 2011 ice-free season. The estimate for the 2012 survey was 83 bears (SE 4.5) in the 2012 study area. Thus, combining the aerial survey results from 2011 and 2012 yielded an overall estimate of 943 (SE: 174, 95% CI: 658–1350) for SH (Obbard et al. 2015).

Overall, despite the difference in methodologies, assumptions, and biases between capture–recapture studies and aerial surveys, the evidence suggests it is likely that the subpopulation was unchanged in abundance since the mid-1980s. However, body condition and body size declined since then, and duration of sea ice decreased by about 30 days from 1980 to 2012 (Obbard et al. 2016). Therefore, due to the conflicting information on subpopulation status combined with ongoing changes in sea ice, the intensive aerial survey was repeated in September 2016 to assess recent trend in abundance.  All areas in Ontario, Nunavut and Québec were sampled within a 3-week period to ensure complete coverage within the same year. . Results of that survey suggest abundance declined 17% from 943 bears (95% CI: 658–1350) in 2011/2012 to 780 (95% CI: 590–1029) in 2016 (Obbard et al. 2018). The proportion of yearlings declined from 12% of the population in 2011 to 5% in 2016, whereas the proportion of cubs remained similar (16% in 2011 vs. 19% in 2016) suggesting low survival of the 2015 cohort.  Low survival of cubs and other subadults is one predicted demographic effect of climate warming (Derocher et al. 2004).  It is unknown whether the low survival of the 2015 cohort is a one-time event or indicative of a trend.  However, sea ice duration is predicted to continue to decline in SH (Castro de la Guardia et al. 2013) so further declines in body condition, survival and abundance are likely.

References

Castro de la Guardia, L., A.E. Derocher, P.G. Myers, A.D. Terwisscha van Scheltinga, and N.J. Lunn. 2013. Future sea ice conditions in Western Hudson Bay and consequences for polar bears in the 21st century. Global Change Biology 19: 2675-2687.

Derocher, A.E., N.J. Lunn, and I. Stirling. 2004. Polar bears in a warming climate. Integrative and Comparative Biology 44: 163-176.

Jonkel, C., P. Smith, I. Stirling, and G.B. Kolenosky. 1976. The present status of the polar bear in the James Bay and Belcher Islands area. Canadian Wildlife Service Occasional Paper 26. 42 p.

Kolenosky, G.B. and J.P. Prevett. 1983. Productivity and maternity denning of polar bears in Ontario. International Conference on Bear Research and Management 5: 238-245.

Kolenosky, G.B., K.F. Abraham, and C.J. Greenwood. 1992. Polar bears of Southern Hudson Bay. Polar bear project, 1984-88: Final report. Ontario Ministry of Natural Resources, Maple, ON. 107 p.

Lunn, N.J., M. Taylor, W. Calvert, I. Stirling, M. Obbard, C. Elliott, G. Lamontagne, J. Schaeffer, S. Atkinson, D. Clark, E. Bowden, and B. Doidge. 1998. Polar bear management in Canada 1993-1996. In Polar Bears: Proceedings of the Twelfth Working Meeting of the IUCN/SSC Polar Bear Specialist Group, Edited by A.E. Derocher, G.W. Garner, N.J. Lunn, and Ø. Wiig. IUCN, Gland, Switzerland and Cambridge, UK.

Middel, K.R. 2013. Movement parameters and space use for the Southern Hudson Bay polar bear subpopulation in the face of a changing climate.  M.Sc. thesis, Trent University, Peterborough, Ontario, Canada. 

Obbard, M.E. 2008. Southern Hudson Bay polar bear project 2003–2005: Final report. Unpublished report, Wildlife Research and Development Section, Ontario Ministry of Natural Resources, Peterborough, ON. 64 p.

Obbard, M.E., M.R.L. Cattet, T. Moody, L.R. Walton, D. Potter, J. Inglis, and C. Chenier. 2006. Temporal trends in the body condition of Southern Hudson Bay polar bears. Climate Change Research Information Note, No. 3. Ontario Ministry of Natural Resources, Applied Research and Development Branch, Sault Ste. Marie, Ontario, Canada. 8 p.

Obbard, M.E., M.R.L. Cattet, E.J. Howe, K.R. Middel, E.J. Newton, G.B. Kolenosky, K.F. Abraham, and C.J. Greenwood.  2016.  Trends in body condition in polar bears (Ursus maritimus) from the Southern Hudson Bay subpopulation in relation to changes in sea ice.  Arctic Science 2:15-32.

Obbard, M.E., T.L. McDonald, E.J. Howe, E.V. Regehr, and E.S. Richardson. 2007. Polar bear population status in Southern Hudson Bay, Canada. 2007. U.S. Geological Survey, Reston, Virginia, USA.

Obbard, M.E., and K.R. Middel. 2012. Bounding the Southern Hudson Bay polar bear subpopulation. Ursus 23:134-144.

Obbard, M.E., S. Stapleton, K.R. Middel, I. Thibault, V. Brodeur, and C. Jutras. 2015. Estimating the abundance of the Southern Hudson Bay polar bear subpopulation with aerial surveys. Polar Biology 38:1713-1725.

Obbard, M.E., S. Stapleton, G. Szor, K.R. Middel, C. Jutras, and M. Dyck. 2018. Re-assessing abundance of Southern Hudson Bay polar bears by aerial survey: effects of climate change at the southern edge of the range. Arctic Science 4: 634-655.

Obbard, M.E., and L.R. Walton. 2004. The importance of Polar Bear Provincial Park to the Southern Hudson Bay polar bear population in the context of future climate change. In C.K. Rehbein, J.G. Nelson, T.J. Beechey, and R.J. Payne, editors. Parks and protected areas research in Ontario, 2004: planning northern parks and protected areas: proceedings of the Parks Research Forum of Ontario annual general meeting, May 4-6, 2004. Parks Research Forum of Ontario, Waterloo, Ontario, Canada.