Alaska Department of Fish and Game
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Did You Know?
Polar bears are closely related to brown bears.
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.
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.
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.
Polar bears’ movements are driven by regional ice dynamics. Their migrations can be quite extensive, following the seasonal position of the ice edge.
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
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)
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.
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.
Males: 600–1200 lbs. 8–10 ft.; Females: 400–700 lbs.
Circumpolar, northern hemisphere only
Ringed seals, bearded seals, walruses, beluga whales
Male polar bears, and Alaska Native hunters
2 cubs once every 3 years
Did You Know?
- Polar bears have black skin underneath their white fur.
- Polar bears do not undergo true hibernation.
- Polar bears are closely related to brown bears.
- The polar bear’s white coat serves as camouflage while hunting on snow and sea ice.
Polar bears are hunted by Alaska Natives as an important part of their culture. Polar bear meat is consumed, and their fur is used for clothing and blankets. Parts of the bear are also used for handicrafts.
Polar bears are protected under the Marine Mammal Protection Act (MMPA) and managed by the U.S. Fish and Wildlife Service (USFWS). USFWS also has co-management agreements with the Alaska Nanuuq Commission and the North Slope Borough. The Chukchi Sea population is managed through a bilateral agreement with Russia. Alaska Natives have also signed an agreement with the indigenous people of Canada regarding the management of the Southern Beaufort Sea population.
The U.S. Fish and Wildlife Service (USFWS) and U.S. Geological Survey (USGS) conduct polar bear research. They have a long term mark-recapture study in the Southern Beaufort Sea to determine population size and productivity. In 2008, they began a study on the effect of climate change on Southern Beaufort Sea polar bears to compare the condition and activity of polar bears on land versus on the ice. USFWS conducts yearly aerial surveys of Southern Beaufort Sea polar bears to study their fall distribution. USFWS and USGS also study polar bears in the Chukchi Sea. Through a capture project, the scientists collected biological and demographic information.
ADF&G and the USFWS-Marine Mammals Management are collaborating on a project to evaluate the feasibility of 3 methods to detect polar bear dens on barrier islands in the Beaufort Sea. For more information see Cooperative Maternal Polar Bear Den Detection Project.
For more information on USFWS polar bear research, see the USFWS Polar Bear Research in Alaska (PDF file).
If you find a polar bear carcass see the USFWS Polar Bear Research in Alaska (PDF file).
- Polar Bear — Wildlife Notebook Series (PDF 43 kB)
- Polar Bear — U.S. Fish and Wildlife Service
- Polar Bear — ADF&G Comprehensive Wildlife Conservation Strategy (see pg. 7) (PDF 186 kB)
- Polar Bear Safety (PDF file)