PANEL 3: POLAR BEAR STUDIES Further Notes on Polar Bear Denning Habits

Polar bears construct maternity dens in the snow throughout their range. The Owl River maternity denning a r e a on the Manitoba coast of Hudson Bay, Canada, had a measured productivity of 100-150 cubs in 1970 and 1971. Maternity denning is now confirmed for the Twin Islands in James Bay, but estimates of productivity for James Bay and the Ontario coast of Hudson Bay should still be made. Female polar bea rs build a variety of dens in the vicinity of their winter dens and along their route a s they move to the sea ice. This makes the censusing of maternity dens and estimating of productivity difficult. The winter dens in Hudson and James bays differ from high arc t ic dens in that earth chambers a r e used, with snow dens added a s winter progresses. Summer denning occurs along the Manitoba and Ontario coasts of Hudson Bay, and on the islands in James Bay. Surface pits, shallow dens and deep burrows a r e the three basic types of ear th dens built. All three types appear to be con-structed for temperature regulation by the bears, but each type is sometimes used la ter for shelter, protection from insects, protection from other bea rs or for winter dens. These behavioural adaptations appear significant in delineating a discrete polar bear population for James Bay and southern Hudson Bay