Polar bears live on the coasts of arctic regions and on the frozen expanses of the northern seas. The polar bear lives a solitary life, with the exception of the female that travels with its cubs. Unlike the northern brown bear, the polar bear does not hibernate but remains active throughout the year. Some polar bears spend their summer following the retreating sea ice and hunting seal, some spend the summer on dry land where the food is scarcer, using the fat deposits they have built up during the winter.
The polar bear remains white all year long. Its winter fur has a thicker layer of underfur than its summer fur. The hairs are hollow, so there is a lot of insulating air in the fur. The hair on the paws not only keeps them warm, but also gives extra grip on slippery ice. Under its skin the polar bear may have an up to a 10 cm thick layer of fat that not only works as insulation, but also helps keep the bear afloat when it is swimming. The extra fat deposits are needed also as reserve nutrition, when food becomes scarce. The ears of the polar bear are considerably small in relation to its size. This keeps the surface area and, thus, the heat loss as small as possible. The white colour of the polar bear makes it harder for its prey to detect it in snowy terrain both in the summer and in the winter.