Native to the coldness of the Arctic Circle, the polar bear, apart from being the largest carnivore on land, is also known to be the largest of its kind. A whooping measure of 350 - 680 kg happens to the average weight of an adult male, while the female weighs half of it. The polar bear species happens to be a close kin of the brown bear, however, over time, it has evolved different physical features to adapt to the cold temperatures of the Arctic region. This is the reason why it is able to move across snow, ice and open water for hunting its game; mainly seals. Although, known as the largest terrestrial carnivore, most polar bears spend their time at frozen sea. This feature of theirs has earned them the name, 'maritime bear'. Important Facts About the Polar Bear Habitat Ice, water, islands and continental coastlines make up for the main habitat of these mammals. The sea ice that covers the water over the continental shelf annually and the Arctic inter-island archipelagos are populated by the polar bears. These habitats are preferred by the animals because they offer high biological productivity compared to the deep waters of the high Arctic. Polynyas [(a stretch of open water surrounded by ice (especially in Arctic seas)] and leads (water channels or cracks through ice which may remain open (ice free) for only a few minutes to several month ) also form a part of the habitat of the polar bears. These places are used as a means to hunt seals, which make up for the bulk of the diet of these mammals. Precisely, the perimeter of the polar ice pack is considered as the primary habitat of these predators of the ice, as these places have the highest density of seals. With changing weather, ice recedes and advances and this causes the seals to migrate. As a result, the polar bears too, have to undergo extensive migration in order to follow their prey. In summer, some areas undergo complete meltdown of ice and these areas are inhabited by the polar bears for some time of the year. It is also common to find pregnant females, spending their time in the autumn and winter, in maternity dens. The population of polar bears is known to extend as far south as James Bay in Canada. These bears are known to be the most southerly dwelling bears. Incidents have been reported about the sightings of these mammals as far south as Berlevag on the Norwegian mainland and the Kuril Islands in the Sea of Okhotsk. In the south, places such as southern Labrador, Newfoundland,and Norway witness the visits of the polar bears. During years when it snow heavily, the Gulf of St. Lawrence and Bering Sea are the places which are frequented by the bears. It has been estimated that about 20,000 - 25,000 of polar bears exist world wide, a global population estimation is difficult to achieve though. The polar bear species is listed as vulnerable by the IUCN (International Union for Conservation of Nature). It is assumed that global warming will be the prime factor in the reduction of a certain percentage of the population of these mammals in the coming three generations. WWF (World Wildlife Fund) regards these carnivores as one of the important indicating factors of the major changes in the Arctic. When these mammals come under any kind of risks, it may signify that there is something amiss with the Arctic marine ecosystem.