The Polar Bear
Polar bears live in the circumpolar north in areas where they can hunt their primary prey, ice seals. They are found in Canada (home to roughly 60% of the world's polar bears), the U.S. (Alaska), Greenland, Russia, and Norway (the Svalbard archipelago).
Fur. Polar bears' fur consists of a dense, insulating underfur topped by guard hairs of various lengths. It is not actually white—it just looks that way.
Each hair shaft is pigment-free and transparent with a hollow core that scatters and reflects visible light, much like what happens with ice and snow.
Polar bears look whitest when they are clean and in high angle sunlight, especially just after the molt period, which usually begins in spring and is complete by late summer. Before molting, accumulated oils in their fur from the seals they eat can make them look yellow.
Skin. Polar bears have black skin under which there is a layer of fat that can measure up to 4.5 inches (11.5 centimeters) thick.
- On land (or on top of the sea ice) the polar bear's thick fur coat--not its fat—prevents nearly any heat loss. In fact, adult males can quickly overheat when they run.
- In the water, polar bears rely more on their fat layer to keep warm: wet fur is a poor insulator. This is why mother bears are so reluctant to swim with young cubs in the spring: the cubs just don't have enough fat. - http://www.polarbearsinternational.org/about-polar-bears/essentials
Polar bears are highly dependent on older stable pack ice in the Arctic region, where they spend much of their time on the ice hunting, mating and denning. They are generally solitary as adults, except during breeding and cub rearing. Polar bears are strong swimmers, and individuals have been seen in open Arctic waters as far as 200 miles from land, although swimming long distances is not preferred since it requires so much energy for adults and can be fatal to younger bears. Pregnant polar bears need to eat a lot in the summer and fall build up enough fat reserves to survive the denning period. They seek out maternity dens in October or November. Most maternity dens are located on land where snow accumulates including along coastal bluffs, river banks or pressure ridges on sea ice. Sows give birth to usually 1 or 2 one-pound cubs and then nurse them until they reach about 20-30 pounds before emerging from the den in March or April. - http://www.defenders.org/polar-bear/basic-facts#