Fish and Game Home

Alaska Department of Fish and Game


Jump to species:

Printer friendly

Polar Bear (Ursus maritimus)
Species Profile

Photo of a Polar Bear

Did You Know?

The polar bear’s white coat serves as camouflage while hunting on snow and sea ice.

Special Status Listing: Yes, see Status, Trends and Threats.

General Description

Polar bears have longer necks, and smaller heads and ears compared to other bears. Their white or yellowish coat is made of water repellant hair on top of a dense undercoat. They have large feet to help them swim and walk on thin ice. The bottoms of their feet are nearly covered in fur.

Polar bears are the size of large brown bears. The largest males can weigh in excess of 1700 lbs, but the average is 600–1200 lbs and 8–10 feet in length. Adult females weigh 400–700 lbs.

Life History

Growth and Reproduction

Females are sexually mature when they are 3–6 years old. Males reach sexual maturity at 4-5 years of age, but are generally not successful breeders until after 6 years of age. The breeding season for polar bears is March through May. A male will find a female by following her scent and tracks across the sea ice. After mating, the development of the fertilized egg (blastocyst) is delayed and does not implant in the female’s uterus until August. Once the embryo begins to grow, the gestation period is only 4-5 months. In October and November, a pregnant female will find a denning area either on land or on the sea ice. She creates her den by making a depression in the snow on a bank or slope or near rough ice. As snow drifts form, she will increase the size of her den. The cubs (usually twins) are born in December and weigh 1-2 lbs and must remain in the protection of the den until they grow bigger.

By late March or early April when the cubs weigh ~15 lbs, they leave the den. For the first few days, the family will make short trips and return to the den giving the cubs time to acclimate to the temperatures outside. After this time, the group will travel to the drifting sea ice. The cubs will remain with their mother for about 2 years and then the female will mate again.

Food Ecology

Ringed seals are the main prey of polar bears. Bears capture seals by waiting at their breathing holes. They may also hunt seals that are resting on the ice or they break into seal dens, called lairs, made in the snow and capture females or pups. Polar bears also eat bearded seals, walrus, and beluga whales. Polar bears will feed on whale, walrus, and seal carcasses they find. When other food is not available, they will eat small mammals, bird eggs, and vegetation.

Migration

Polar bears’ movements are driven by regional ice dynamics. Their migrations can be quite extensive, following the seasonal position of the ice edge.

Behavior

In general, except for females with cubs, polar bears are solitary animals, however whale carcasses can attract large numbers of polar bears.

Range and Habitat

Polar bears occur throughout the northern polar region. In the winter, polar bears in Alaska are found as far south as St. Lawrence Island and occasionally move down to St. Matthew Island and the Kuskokwim Delta. In the summer, bears are most abundant around the edge of the pack ice in the Chukchi Sea and Arctic Ocean. Denning areas include Wrangel Island and other Russian Islands, islands in the Canadian Arctic, Greenland, and Spitsbergen, and the northern Alaska coast.

Mark-recapture, tagging, and genetic studies have shown that there are 19 separate populations of polar bears. Two of these populations are in Alaska: the Southern Beaufort Sea population and the Chukchi Sea population. The Southern Beaufort Sea population is found along the north coast of Alaska and into the Canadian Beaufort Sea area. The Chukchi Sea population is in western Alaska, ranging as far west as Wrangel Island and eastern Siberia and as far south as St Matthew Island in the Bering Sea.

Status, Trends, and Threats

Status

The two stocks in Alaska appear to be stable. However, the polar bear is listed as threatened under the Endangered Species Act (ESA) because their dependence on sea ice for hunting is likely to cause population declines in the future. To learn more, visit the ADF&G Special Status page for polar bear.

NatureServe: Global: G3 (vulnerable), State: S3 (vulnerable)
IUCN: Vulnerable
ESA: Threatened

Trends

The population of polar bears in Alaska declined during the early 1970s. This decline was attributed to overharvest in the 1950s and 1960s when a trophy harvest was legal and popular. There was a moderate recovery during the late 1970s after the passage of the Marine Mammal Protection Act (MMPA) in 1972 when only subsistence hunting by Alaska Natives was allowed. In 2009 the Southern Beaufort Sea population was estimated to be 1,500 and the Chukchi Sea population was not as well known, but thought to be ~2,000.

Threats

Current and predicted future declines in sea ice led the U.S. Fish and Wildlife Service to find that the polar bear should be listed as threatened throughout its range. Thinner ice and longer ice-free periods in summer may reduce the length of time polar bears have to hunt and result in a decreasing population.

Oil exploration and drilling activities are also a threat; bears can be displaced from high quality denning areas into less suitable locations. Contact with oil during an oil spill could reduce the insulation capacity of their coat and be toxic to bears. It could also negatively impact their food.

Fast Facts

  • Size
    Males: 600–1200 lbs. 8–10 ft.; Females: 400–700 lbs.
  • Lifespan
    25 years
  • Distribution/Range
    Circumpolar, northern hemisphere only
  • Diet
    Ringed seals, bearded seals, walruses, beluga whales
  • Predators
    Male polar bears, and Alaska Native hunters
  • Reproduction
    2 cubs once every 3 years