The fur of a polar bear is different from the fur of all other mammals. The hairs are about 2.5 to 5 cm long (1 to 3 inches) and look like clear glass straws. These hairs carry the warm sunlight down to the polar bear's black skin. Other smaller hairs near the skin help trap this heat. The polar bear is able to stay warm, even when it's cold.

A layer of fat beneath the polar bear's skin keeps it from freezing during the long cold winter. If the weather gets too cold, the polar bear digs a hole in the snow and sleeps until it is warmer outside.

For several weeks during May or June, polar bears shed their fur and grow a whole new coat. This shedding is called moulting.