Posted on April, 01 2006

The cub survival rate for the Southern Beaufort Sea polar bear population is declining according to a joint study by the US Geological Survey (USGS) and the Canadian Wildlife Service.

Cub survival rate is currently 43 percent compared with 65 percent in the early 1990s.

Although the researchers could not detect whether the actual population size has changed, they found that other indicators of the population’s health are generally in decline. Along wi th a de c reas e i n the number of cubs surviving, the researchers also found that the physical size of the bears is declining.

Steve Amstrup, wildlife biologist with the USGS and co-author of the study, said: “The things we’re observing are consistent with a population that is undergoing nutritional stress. We can’t say definitively it’s because of changes in the sea ice, but we don’t know what else it would be.”

The findings of this study parallel findings in the Western Hudson Bay polar bear population in Canada, where changes in cub survival and bear size preceded detection of a decline in the overall population. Those changes were correlated with longer ice-free periods in Hudson Bay.

During the course of the study, the ice-free season in areas of preferred polar bear habitat in the Southern Beaufort Sea increased from 82 days to 138 days, and changes in the population dynamics of polar bears may be related, as they were found to be in Hudson Bay.

Eric V. Regehr (USGS) and Ian Stirling (Canadian Wildlife Service) were also co-authors of the study. The report is available online at: pubs.usgs.gov/of/2006/1337/.

Nigel Allan nallan@wwf.no