Polar bears evolved from brown bears and are the largest member of the bear family. Male polar bears measure 2.4- 2.6 m (8-9 ft) from nose to tail and generally weigh up to 600 kg (1,320 lbs), but may reach up to 800 kg (1,760 lbs). Females measure around 2 m (6-7 ft) and are typically about half the weight of males.
Designated critical habitat includes three units: barrier islands, sea ice and terrestrial denning habitat. The total area designated covers 484,734 sq km (187,157 sq mi), with approximately 96 percent of the critical habitat area being sea ice.
The Barrier Island Habitat includes coastal barrier islands and spits along Alaska’s coast. Barrier island habitat is used by polar bears for denning, refuge from human disturbances, access to maternal dens and feeding habitat, and travel along the coast.
The Sea Ice Habitat islocated over the continental shelf includes water 300m and less in depth. Sea ice habitat is essential to most polar bear activities. Polar bears evolved over thousands of years to life in a sea ice environment. They depend on the sea ice-dominated ecosystem to support essential life functions. It provides a platform for hunting and feeding, for seeking mates and breeding, for movement to terrestrial maternity denning areas, for resting, and for long-distance movements.
The Terrestrial Denning Habitat includes lands within 32 km of the northern coast of Alaska between the U.S. Canadian border and the Kavik River and within 8 km between the Kavik River and Barrow. Appropriate terrestrial denning habitat typically occurs near the coast which allows females to prey on seals, so that they can meet their nutritional needs before and after denning. Adult females also select locations that will provide an environment safe from predatory adult males, disturbance, and adverse weather conditions; all risks to which cubs are particularly vulnerable.
Nineteen populations of polar bears are distributed in Alaska, Canada, Greenland, Norway, and Russia. The world wide population is estimated to be 22,000-25,000 bears. Two populations occur in Alaska: the southern Beaufort Sea stock, shared with Canada; and the Bering Chukchi/Seas stock, shared with the Russian Federation.
To the left is a map of the 19 polar bear subpopulations (source: Polar Bear Specialist Group . The subpopulations include: Southern Beaufort Sea (SB), Chukchi Sea, Laptev Sea, Kara Sea, Barents Sea, East Greenland, Northern Beaufort (NB), Kane Basin (KB), Norwegian Bay (NW), Lancaster Sound (LS), Gulf of Boothia (GB), M’Clintock Channel (MC), Viscount Melville Sound (VM), Baffin Bay, Davis Strait, Foxe Basin, Western Hudson Bay (WH), Southern Hudson Bay and the Arctic Basin (AB).
Thanks to the hard work of a diverse team of stakeholders, known as the Polar Bear Recovery Team , the Polar Bear Conservation Management Plan (Plan) is now complete. The Plan serves as a practical guide to implementation of polar bear conservation in the United States. It describes the conditions under which polar bears would no longer need the protections of the Endangered Species Act and lays out a collective strategy geared towards achieving those conditions. A parallel path is laid out for improving the status of polar bears under the Marine Mammal Protection Act.