The bears' snow-white coats help them blend into their surroundings and stay hidden from their prey. A polar bear's staple food is the ringed seal. The bears either wait beside holes in the ice for seals to surface, or sneak up on them across the ice. Bears sometimes dig down into seal dens beneath the surface snow and eat newborn pups.
Polar bears put on a lot of weight in summer because they have less opportunity to feed in winter. They often take shelter from extreme weather in underground dens. Pregnant females sleep inside large dens for long periods during the winter months, before giving birth to their cubs in spring. The young stay with their mother for two years.