Polar bears mate in the spring, particularly in April. During this time, the males wander over long distances, looking for females without cubs. Most females breed every three years when their young have left.
The female bear digs out her den during October and November, to a depth of 1 to 3 metres under the snow, often on a steep south-facing slope of a hill where northerly winds blow the snow into large piles. A den usually consists of a tunnel leading into a large chamber. The temperature inside the den can be 4.4 degrees Celcius warmer than the outside air temperature.
The cubs, usually two, are born in November or December, after a gestation period of 7 - 8 months, and are only the size of a rat, weighing 450 - 900g. To begin with they are blind and hairless. Feeding on their mother's rich milk, they grow very quickly and when they leave the den in March or April, they are about the size of a domestic cat. The cubs leave their mother in the third spring of their life.Read More: Food and Hunting