Posted on November 17, 2020
Final reports for two Canadian subpopulations reveal the number of polar bears in M’Clintock Channel has more than doubled since 2000 while Gulf of Boothia as remained about the same despite moderate declines in summer sea ice cover. All of the survey results were published online yesterday (16 November 2020) and I was alerted to the posting this morning via email by a Nunavut employee.
2014-2016 via genetic biopsy darting
Dyck, Lukacs, and Ware (2020) summary:
- Mean abundance estimate 716 (range 545 – 955) for 2014-2016.
compared to 284 (range 225-343) for 1998-2000 (Taylor et al. 2006), so population size more than doubled between study periods.
- Numbers of males and females increased between study periods due to reduced hunting and ‘improved habitat quality.’
- Population has recovered from previous overharvest (1970s-1990s).
Sea ice decline: Note that according to the IUCN 2015 polar bear assessment report (Regehr et al. 2016 Figure 2), summer sea ice decline for M’Clintock Channel has been similar to Foxe Basin (below). See a discussion (with references) of sea ice decline vs. documented harm to polar bears here.
Gulf of Boothia
2015-2017 via genetic biopsy darting
Dyck, Regehr, and Ware (2020) summary:
- Mean abundance estimate 1525 (range 1231-1819) for 2015–2017 compared to 1592 (range 1231-1953) in 1998-2000 (Taylor et al. 2009), so about the same.
- Mean litter sizes showed no trend between study periods.
- Mean cub-of-the-year litter sizes were 1.61 (range 1.51 – 1.70), which is about as high as any population reported and similar to Western Hudson Bay in 2016 and Kane Basin in 2014 (Crockford 2020).
- Mean yearling litter sizes were 1.53 (1.41 – 1.64).
- Body condition (i.e., fatness) in the spring increased between the study periods.
- Survival rate for adult females was higher than adult males (0.95 vs. 0.85).
- Abundance of adult females increased from 0.57 to 0.61 between the study periods.
- Population survival indicators suggest a ‘good potential for growth’.
Sea ice decline: Note that according to the IUCN 2015 polar bear assessment report calculations (Regehr et al. 2016 Figure 2), summer sea ice decline for Gulf of Boothia has been similar to the Southern Beaufort:
Crockford, S.J. 2020. State of the Polar Bear Report 2019. Global Warming Policy Foundation Report 39, London. Pdf here.
Dyck, M., Lukacs, P., and Ware, J.V. 2020. Re-estimating the abundance of a recovering polar bear subpopulation by genetic mark-recapture in M’Clintock Channel, Nunavut, Canada. Final Report, Government of Nunavut, Department of Environment, Iglulik. 29 July 2020. Pdf here.
Dyck, M., Regehr, E.V. and Ware, J.V. 2020. Assessment of Abundance for the Gulf of Boothia Polar Bear Subpopulation Using Genetic Mark-Recapture. Final Report, Government of Nunavut, Department of Environment, Iglulik. 12 June 2020. Pdf here.
Regehr, E.V., Laidre, K.L, Akçakaya, H.R., Amstrup, S.C., Atwood, T.C., Lunn, N.J., Obbard, M., Stern, H., Thiemann, G.W., & Wiig, Ø. 2016. Conservation status of polar bears (Ursus maritimus) in relation to projected sea-ice declines. Biology Letters 12: 20160556. http://rsbl.royalsocietypublishing.org/content/12/12/20160556 Supplementary data here.
Taylor, M.K., J.L. Laake, P.D. McLoughlin, H.D. Cluff, and F. Messier. 2006a. Demography and population viability of polar bears in the Gulf of Boothia, Nunavut. Government of Nunavut, Department of Environment, Final Wildlife Report #8, Iqaluit. Pdf here.
Taylor, M.K., Laake, J.L., McLoughlin, P.D., Cluff, H.D., Messier, F. 2006b. Demographic parameters and harvest-explicit population viability analysis for polar bears in M’Clintock Channel, Nunavut. Journal of Wildlife Management 70: 1667–1673.
Taylor, M.K., Laake, J.L., McLoughlin, P.D., Cluff, H.D., and Messier, F. 2009. Demography and population viability of polar bears in the Gulf of Boothia, Nunavut. Marine Mammal Science 25:778-796.