Bear beware

Natural History, June, 2004 by Stephan Reebs

Between July and mid-November, polar bears lounge on the shores of Hudson Bay, living off their own fat while they wait for the sea to freeze up. Once the ice is thick enough to support their thousand-pound bulk, the bears can resume hunting for seals, their main source of food. Since the early 1980s, the huge loafing bears have become an autumn tourist bonanza, attracting bus-size tundra vehicles full of curious bear-watchers. The balloon-tired vehicles sometimes come within 130 feet of the bears and stay near them for as long as two hours. Markus G. Dyck and Richard K. Baydack, wildlife biologists at the University of Manitoba in Winnipeg, recently confirmed that such tourism may be seriously disturbing the animals.

The two investigators observed that polar bears interrupt their relaxation and visually scan their environment more often when even one of the large vehicles is on the scene. The bears don't get their rest, because every ten minutes or so another vehicle arrives or leaves. In autumn, the investigators note, polar bears need to just chill out, and the increased vigilance could lead to elevated heart rates and increased output of stress hormones.

Intriguingly, only the males become more vigilant. Dyck and Baydack note that the main danger to a female and her cubs is the male of her own species. When males are preoccupied with tundra vehicles, the females can afford to relax. ("Vigilance behaviour of polar bears (Ursus maritimus) in the context of wildlife-viewing activities at Churchill, Manitoba, Canada," Biological Conservation 116:343-50, 2004)