Polar bear, Ursus maritimus.

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.

Female polar bears first reproduce when they are 6 years old and usually give birth to twin cubs in December or January. The cubs are about 25 cm long at birth and weigh less than one kilogram! Mating occurs in April and May, but the fertilized egg does not implant and begin to grow in the uterus until late September or early October.

Polar bear, Ursus maritimus.

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.

At present, the polar bear is one of the best managed arctic mammals in the world. There are approximately 15,000 polar bears in the Canadian Arctic, of which some 400 are hunted each year.