Polar bears range throughout the circumpolar north in areas where they can hunt seals at open leads. The five "polar bear nations" in which the bears are found include the U.S. (Alaska), Canada, Russia, Denmark (Greenland), and Norway. Polar bears do not live in the southern hemisphere.Scientists estimate that there are between 22,000 to 27,000 polar bears.Adult male polar bears measure 2.5 to 3 meters (8 to 10 feet) tall. They weigh 250 to 770 kilograms (550 to 1,700 pounds). Adult female bears are smaller. They measure 1.8 to 2.5 meters (6 to 8 feet) tall and weigh 90 to 320 kilograms (200 to 700 pounds).Seals are the polar bear's primary prey, particularly the ringed seal and, sometimes, the bearded seal. When hunting is good, polar bears will typically eat only the fat and leave the rest of the carcass for scavengers including arctic foxes, ravens, and younger bears.In the wild, polar bears live an average of 15 to 18 years, although biologists have tagged a few bears in their early 30s.
Polar bears are a potentially threatened species rather than an endangered one. A threatened species is one that could easily become endangered in the foreseeable future. The major threat to the polar bear is climate change. Other threats include pollution, poaching, and industrial disturbances. Hunting could become a threat if populations are not well managed. The U.S. Fish and Wildlife Service has proposed that polar bears be added to the Threatened Species list under the U.S. Endangered Species Act. Canada and Russia both list the polar bear as "a species of concern." In 2005, the world's leading polar bear scientists reclassified the polar bear as vulnerable on the IUCN World Conservation Union's "Red List of Threatened Species," noting that the species could become extinct due to sea ice changes.