Polar bears of SE Greenland get shorefast ice necessary to hunt seals: not so unique after all

The 234 or so polar bears inhabiting the SE tip of Greenland, said to be genetically and ecologically unique because they are “surviving without ice“, have been experiencing sea ice formation along the shoreline this month just like other bears across the Arctic. Recall that shorefast ice formation attracts seals in the fall, which polar bears hunt successfully, and the following spring (April/May) provide a platform for ringed seals to give birth to their pups, which polar bears eat with gay abandon.

The photo above was taken by Kristin Laidre in March 2016: a bear this fat at the end of winter (i.e. before ringed seals are born in the spring) is living in productive habitat.

According to the paper, the land-bound fast ice that most ringed seals use to give birth and nurse their pups in spring (April-May) is still routinely available in SE Greenland (Laidre et al. 2022; McLaren 1958; Stirling and Oritsland 1995).

Here is what polar bear biologist Steve Amstrup (2003:592) has to say about the spring feeding:

In some areas, predation on pups is extensive. Hammill and Smith (1991) estimated that polar bears annually kill up to 44% of new born seal pups if conditions are right.

If this ice lasts only until May 2023, it would be 180 days of productive sea ice and a far cry from the mythical ‘100 days’ which models suggest is the threshold for polar bear demise (Molnár et al. 2010, 2020). This is apparently why polar bears in this region are doing just as well as those living in NE Greenland: in other words, thriving despite the pessimistic prophesies of experts.

Chart below is for 17 December 2022 (MASIE):

The map below shows the boundary of the proposed ‘SE Greenland’ polar bear subpopulation from the paper by Kristen Laidre and colleagues (2022):

References

Amstrup, S.C. 2003. Polar bear (Ursus maritimus). In Wild Mammals of North America, G.A. Feldhamer, B.C. Thompson and J.A. Chapman (eds), pg. 587-610. Johns Hopkins University Press, Baltimore.

Laidre, K.L., Supple, M.A., Born, E.W., et al. 2022. Glacial ice supports a distinct and undocumented polar bear subpopulation persisting in late 21st century sea-ice conditions. Science 376 (6599): 1333-1338. https://www.science.org/doi/10.1126/science.abq5267

McLaren, I.A. 1958. The biology of the ringed seal (Phoca hispida Schreber) in the Eastern Canadian Arctic. Fisheries Research Board of Canada, Ottawa. Bulletin 118. Pdf here.

Molnár, P.K., Bitz, C.M., Holland, M.M., Kay, J.E., Penk, S.R. and Amstrup, S.C. 2020. Fasting season length sets temporal limits for global polar bear persistence. Nature Climate Change 10:732-738.  https://doi.org/10.1038/s41558-020-0818-9

Molnár, P.K., Derocher, A.E., Theimann, G., and Lewis, M.A. 2010. Predicting survival, reproduction and abundance of polar bears under climate change. Biological Conservation 143:1612-1622. http://www.math.ualberta.ca/~mlewis/Publications%202010/Molnar-Derocher-Thiemann-Lewis.pdf

Stirling, I. and Øritsland, N. A. 1995. Relationships between estimates of ringed seal (Phoca hispida) and polar bear (Ursus maritimus) populations in the Canadian Arctic. Canadian Journal of Fisheries and Aquatic Sciences 52: 2594 – 2612. http://www.nrcresearchpress.com/doi/abs/10.1139/f95-849#.VNep0y5v_gU

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December 20, 2022 at 06:46AM

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