ARCUS 16th Annual Meeting and Arctic Forum 2004

Polar Bears, Seals, and Climate in Hudson Bay and the High Arctic

Ian Stirling^1
1Canadian Wildlife Service, 5320 122 St., Edmonton, AB, T6H 3S5, Canada, ian.stirling@ec.gc.ca

From 1981 through 2003, the condition of adult male polar bears and females accompanied by dependent young has declined significantly in western Hudson Bay. This decline is reflected in aspects of reproduction and survival. The average date of breakup of the annual ice on western Hudson Bay is now about 2.5 wks earlier than it was in the early 1970s. There is a significant positive relationship between the time of breakup and the condition of adult males and females (i.e., the earlier the breakup, the poorer the condition of the bears). The trend toward earlier breakup is correlated with steadily warming air temperatures over the study area in spring (0.3-0.4° C from April through June per decade) for the last 50 years.

We suggest that the proximate cause of the decline in physical and reproductive parameters of polar bears in western Hudson Bay over the last 22 years has been the trend toward earlier breakup, which has shortened the most important feeding period for polar bears before their annual period of fasting during the open water season in Hudson Bay. The ultimate factor responsible for the earlier breakup in western Hudson Bay appears to be a long-term warming trend in atmospheric temperatures. Changes in ringed seal and harbour seal populations appear to be underway and are likely to be affecting polar bears but these relationships are not yet well understood.

In the High Arctic, some areas dominated by multiyear ice and low productivity may, in the short term at least, become more biologically productive habitat for polar bears and seals. However, if long-term projections of the disappearance of ice in the polar basin are correct, this improvement in habitat will be temporary. The relationships between polar bears and their prey species will be described to provide an understanding of their dynamic importance. Projections of potential future problems for polar bears and seals in the future will be speculated upon.

Abstract Categories: Past and Potential Consequences