Spatial relationships and behavior of polar bears (Ursus maritimus Phipps) concentrated on land during the ice-free season of Hudson Bay

Abstract

I observed polar bears (Ursus maritimus Phipps) at Cape Churchill, Manitoba, a site where polar bears congregate during the autumn when Hudson Bay is ice free. Adult males, subadult males, and subadult females were spatially segregated to a degree that depended primarily on density. The higher the density, the greater the degree of segregation. Adult males showed the closest intraclass association. Subadult females spent more time in activity than did either adult or subadult males; this may be due to subadult females being approached more by other subadults. Much of an individual's social behavior occurred with members of its own age–sex class, perhaps as a result of spatial segregation. In the noncompetitive situation of this study, polar bears aggregated and were more social than when hunting on the sea ice. This study provides further evidence for the flexibility of carnivore social systems, not only between populations of the same species, but also within a single population.