Polar bear habitat update: Winter conditions well on their way across the Arctic except in Svalbard

From Polar Bear Science

Dr. Susan Crockford

December is late fall in the Arctic: winter conditions are gearing up but are not in full swing everywhere. Sea ice is developing quickly over Hudson Bay and moving slowly towards the Bering Sea but the Svalbard archipelago is still devoid of pack ice.

Such conditions north of Norway have existed most years since 2005: it’s certainly not a new development for Svalbard to be free of surrounding pack ice in December (although there was lots of ice in 2019 and 2021 by late November). This means traditional denning areas on the eastern islands again cannot be used by pregnant polar bear females, because they must be ensconced in their dens by at least late November or so.

Some seem to think this is a calamity: that such ‘loss of habitat’ is a huge concern for the survival of the subpopulation, if not the entire species. However, the same conditions existed in 2011 and did not result in a dramatic decline in the population as measured in 2015 (Aars et al. 2017) because the bears knew how to respond. They have apparently moved north to make maternity dens on the sea ice or east to the Franz Josef Land archipelago in Russia (Aars 2015). These areas are still within the Barents Sea subpopulation boundaries and researchers have known for two decades that bears have moved around within it (Andersen et al. 2012; Derocher 2005; Maurizen et al. 2002).

Sea ice update

Note that for the last few weeks, the Canadian Ice Service charts for most of Hudson Bay ice have only been updating once a week (on Wednesday). This seems to be a perennial problem about this time of year. It may have something to do with glitches in the satellite data, although they offer no explanation for the issue.

Svalbard ice conditions

The image below is from Andersen and colleagues, including Derocher (2012) showing tiny King Karls Land (Kongsoya or Kong Karis Land) maternity dens as they were more than a decade ago. These islands are not used for denning if the pack ice doesn’t reach them by about mid- to late November.

While it is certainly true that the Svalbard/Barents Sea region has lost more ice than any other subpopulation area (Regehr et al. 2016), it is also true that polar bear have not been negatively impacted by this change. Contrary to expectations, studies since then have shown the bears are thriving: in part, because ice around Svalbard has still been available during the critical spring feeding and mating period (Aars et al. 2017; Lippold et al. 2019).

Moreover, the response of polar bears to this change in sea ice conditions is not unprecedented. There is evidence of a similar movement of ringed seals and polar bears out of the Beaufort Sea when spring ice conditions were especially heavy in 1974/1975, as they were the previous year (1973/1974).

Marine mammal biologist John Burns noted the following in 1975 (Burns et al. 1975:77 pdf below):

“During the period 9 to 19 June [1975] extensive aerial surveys of ringed seals were undertaken in areas of land fast ice between Barter Island and Point Lay. ..The necessity of conducting these surveys was based on observations during the winter of 1974-1975, which indicated unusually high densities of ringed seals in the Chukchi Sea and the reverse in the Beaufort Sea. Observations for the Beaufort Sea were obtained by [Jack] Lentfer (personal communication).

In short, polar bears have strategies to deal with fairly dramatic changes in sea ice habitat because such changes have always existed in their world: most bears don’t just stick to a rigid plan if it threatens their survival, even if some biologists assume they would.

References

Aars, J. 2015. Research on polar bears at Norwegian Polar Institute. Online seminar (‘webinar”), January 14. pdf here.

Aars, J., Marques,T.A, Lone, K., Anderson, M., Wiig, Ø., Fløystad, I.M.B., Hagen, S.B. and Buckland, S.T. 2017. The number and distribution of polar bears in the western Barents Sea. Polar Research 36:1. 1374125. doi:10.1080/17518369.2017.1374125

Andersen, M., Derocher, A.E., Wiig, Ø. and Aars, J. 2012. Polar bear (Ursus maritimus) maternity den distribution in Svalbard, Norway. Polar Biology 35:499-508.

Burns, J.J., Fay, F.H., and Shapiro, L.H. 1975. The relationships of marine mammal distributions, densities, and activities to sea ice conditions (Quarterly report for quarter ending September 30, 1975, projects #248 and 249). In Environmental Assessment of the Alaskan Continental Shelf, Principal Investigators’ Reports, July-September 1975, Volume 1. NOAA Environmental Research Laboratories, Boulder, Colorado. pp. 77-78. Pdf here.

Derocher 2005. Population ecology of polar bears at Svalbard, Norway. Population Ecology 47:267-275.
http://www.springerlink.com.ezproxy.library.uvic.ca/content/765147518rp35613/fulltext.pdf

Lippold, A., Bourgeon, S., Aars, J., Andersen, M., Polder, A., Lyche, J.L., Bytingsvik, J., Jenssen, B.M., Derocher, A.E., Welker, J.M. and Routti, H. 2019. Temporal trends of persistent organic pollutants in Barents Sea polar bears (Ursus maritimus) in relation to changes in feeding habits and body condition. Environmental Science and Technology 53(2):984-995.

Mauritzen, M., Derocher, A.E., Wiig, Ø., Belikov, S.E., Boltunov, A.N., Hansen, E. and Garner, G.W. 2002. Using satellite telemetry to define spatial population structure in polar bears in the Norwegian and western Russian Arctic. Journal of Applied Ecology 39:79-90. http://onlinelibrary.wiley.com/doi/10.1046/j.1365-2664.2002.00690.x/abstract

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