The polar bear, Ursus maritimus, is the largest terrestrial carnivore in the world, although its Latin name means "bear of the sea." Adult males do not reach their maximum size, approximately 500-600 kg, until their eighth to tenth year. Females weigh about half as much as males and attain this size around the age of five or six, the same time they become sexually mature.
Polar bears are active year-round, and prefer areas with sufficient pack ice
to enable them to hunt for seals. The animals generally move south in winter
and north in spring, staying close to the ice belt where ringed seals are most
abundant. Polar bears also catch bearded seals, and occasionally kill walruses,
beluga whales, and narwhals. If trapped on land, especially in the southern
portions of their range, polar bears consume fish, birds, lemmings, carrion,
and berries. They often venture hundreds of kilometres out to sea, and can end
up as far south as Newfoundland and the Gulf of St. Lawrence, adrift on ice
floes that have been caught in strong oceanic currents.
Pregnant females move to specific denning areas; one of the world's largest
sites occurs near Churchill, Manitoba. Other significant sites in Canada include
Banks Island, Southampton Island, and Baffin Island. The mother and cubs remain
in the den until April and then travel together for two years.