The significance of supplemental food to polar bears during the ice-free period of Hudson Bay

Abstract

Polar bears were studied near Churchill, Manitoba, to evaluate the possible importance of supplemental food. Once ashore, bears became segregated by age and sex; family groups and pregnant females moved inland into a denning area, while single bears, especially adult males, remained along the coast. Bears were inactive and fed little. Analysis of blood samples taken from bears in the denning area suggested that they also were not feeding. By remaining active, they are able to minimize energetic demands and the chance of hyperthermia. After 2 months ashore, some bears, mainly family groups and subadults, fed in the Churchill dump. The data indicated that individual needs and learning were major factors determining which bears used the dump. Adult males did not feed there even though they may have been there previously as cubs or subadults. Bears which fed in the dump were significantly heavier than those which did not. There was no evidence that bears using the dump gained either reproductive or survival advantages. We conclude that polar bears will use supplemental food sources which are available or if they have previously learned their location; however, it is not necessary for their survival.