Polar Bears: Giants of the Arctic

Polar bears (Ursus maritimus) are close relatives of brown bears but have evolved to thrive in snowy, icy habitats, inhabiting some of the coldest regions in North America. Their black skin helps absorb heat from the sun, while their thick, white fur provides insulation, repels water, and offers camouflage against the snow and ice. Large, webbed paws make them exceptional swimmers, allowing them to navigate the Arctic waters with ease.

In the United States, polar bears are found exclusively in Alaska. Two subpopulations utilize Alaskan territory at different points in their life cycle: the Chukchi Sea subpopulation, estimated at around 3,000 bears, and the Southern Beaufort subpopulation, which has roughly 900 individuals. Only two U.S. national park units—Bering Land Bridge National Preserve and Cape Krusenstern National Monument—are known to have polar bears in proximity, with some bears’ home ranges extending into park boundaries. For specific information about polar bears in any national park, it’s best to contact the park directly.

Diet and Feeding

Polar bears consume a diet much richer in fat and protein than other bear species. Their main prey are seals, though they will also scavenge whale carcasses when available. With an exceptional sense of smell, polar bears can detect prey or carcasses from nearly 20 miles away. When on land and primary food sources are scarce, they may eat marine mammal remains, birds, fish, terrestrial mammals, and even berries.

Winter Dens

Pregnant female polar bears are the only ones that spend the winter in dens, as hunting for seals on sea ice is most productive during this season. Dens can be located on land along the coast or on sea ice. Unlike black and brown bears, which enter a deep metabolic dormancy during hibernation, denning polar bears remain somewhat active throughout the winter months while nurturing their unborn cubs.

Reproduction and Life Cycle

Mating usually occurs between March and June, but embryo implantation is delayed until autumn. Polar bears give birth during the winter to one to three cubs, with twins being the most common.

Newborn cubs are typically 12–14 inches long and weigh just over one pound. In spring, the mother and her cubs emerge from the den.

Mother polar bears are highly protective, sometimes defending their young from adult males, which can pose a threat to cubs. Cubs grow quickly, remaining with their mother for a little more than two years as they learn essential survival skills in the harsh Arctic environment.