Declining fall weights of female polar bears, western Hudson Bay, 1980 to 2007
Box 10. Declines in polar bear body condition
Changes in sea ice over the past two decades have led to significant declines in physical condition of bears in the western Hudson Bay [277, 299], southern Hudson Bay [300], and Baffin Bay populations [279]. Regehr et al. 2007 [278] showed that survival decreased in association with earlier sea ice break-up and that this contributed to a 22% decline in the size of the western Hudson Bay polar bear population between 1987 and 2004. Reduced survivorship in relation to sea ice conditions has also been demonstrated in the southern Beaufort Sea polar bear population [301].
For the western Hudson Bay population, the body condition of bears measured during the ice-free period declined from 1980 to 2007, as did the average weight of female polar bears in the fall (Figure 30). The female bears weighed were suspected to be pregnant.
For the Baffin Bay population, the decline in body condition since the early 1990s is associated with deteriorating ice conditions [279]. Polar bears were in significantly worse condition in years with less summer sea ice cover, starting in the 1990s when ice in these regions began its sharp decline (Table 2).
Figure 30. Declining fall weights of female polar bears, western Hudson Bay, 1980 to 2007 Body weights were estimated for females on their own, and thus likely to be pregnant. Source: Stirling and Derocher 2012 [269]
Conservation of Arctic Flora and Fauna (CAFF) The data can be downloaded freely. Users are requested to reference the source. Eamer, J., Donaldson, G.M., Gaston, A.J., Kosobokova, K.N., Lárusson, K.F., Melnikov, I.A., Reist, J.D., Richardson, E., Staples, L., von Quillfeldt, C.H. 2013. Life Linked to Ice: A guide to sea-ice-associated biodiversity in this time of rapid change. CAFF Assessment Series No. 10. Conservation of Arctic Flora and Fauna, Iceland. ISBN: 978-9935-431-25-7.
269. Stirling, I., and Derocher, A.E. 2012. Effects of climate warming on polar bears: A review of the evidence. Global Change Biology 18(9): 2694-2706. doi:10.1111/j.1365-2486.2012.02753.x.
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