They are solitary animals and are active at all times of the year. Polar bears are excellent swimmers, and can cruise through the water at 6 miles per hour, using only their front legs. With their eyes open, and their nostrils closed they can dive under water and remain submerged for two minutes. The polar bear's skin is black to absorb heat, and its long guard hairs are hollow to act as an insulator and for buoyancy. In addition, except for the balls of the feet, the soles are covered with hair, making a non-skid tread.
Females breed every third year after separating from their young.
In October or November the bears dig dens in the snow or tundra to give birth to their young. At birth, the young are blind, hairless and deaf, and weigh about 16-32 oz. They first emerge from the den in March or April and will remain with their mothers into the third spring of their lives. Conservation projects and regulated hunting exist in all countries where polar bears exist. Present world population about 40,000 individuals.