The polar bear (scientific Latin name Ursus maritimus), also known as white bear or northern bear, is a large mammal of the order Carnivora (meat eater), family Ursidae (bears). It is a circumpolar species found in and around the Arctic Ocean and is the world’s largest land carnivore. Adult males weigh from 400 to 600 kg (900 to 1300 lbs) and occasionally exceed 800 kg (1750 lbs). Females are about half the size of males and normally weigh 200–300 kg (450 – 650 lbs). Adult males measure 2.4 to 2.6 m; females, 1.9 to 2.1 m. At birth, cubs weigh 600 to 700 g. Population estimates range from 16,000 to 35,000, with about 60% in Canada.
The polar bear is instantly recognizable by its white-colored coat. Unlike other arctic mammals, it never sheds this coat for a darker color in the summer. The hair is not pigmented white; it is unpigmented and hollow, like white hair in humans.
Polar bears are well insulated to the point where they overheat at temperatures above 10°C (50?F). Their insulation is so effective that when viewed with infrared camera they are barely visible. Only the pads of their feet emit detectable heat.
It is the most completely carnivorous member of the bear family and feeds mainly on seals. Polar bears are excellent swimmers and can often be seen in open waters miles from land. This may be a sign that they have begun aquatic adaptations to better catch their prey. They also hunt very efficiently on land due to their prodigious speed; they are more than capable of outrunning a human. Other prey include beluga whales, walruses and rodents. As a pure carnivore predating upon fish-eating carnivores, the polar bear ingests large amounts of Vitamin A, which is stored in its liver: in the past, humans have been poisoned by eating liver of polar bears. Contrary to popular belief, polar bears do not eat penguins: this is because polar bears live at the North Pole, and penguins live (primarily) at the South Pole.
Polar bears are believed to be threatened, not mainly by hunting, but by habitat loss caused by global warming; for example, the area of ice covering Hudson Bay in Northern Canada in winter is shrinking, limiting their access to seal prey. The sensitivity of the survival rates of the bears to global temperature was documented by the population bulge in the cohort of bears born during the transient cooling that followed the eruption of Mount Pinatubo in 1991. However, it turned out that the population of polar bears grew by an unprecedented 15–25 percent between 1995 and 2005. The decrease in several regions was caused by hunting, not by climate change.