Ursus maritimus
Male polar bears average 900 lbs. and females average about 500 lbs., although at least one male is known to have topped 2,200 lbs. Males can be over 3 meters in length. These carnivorous mammals will dine on nearly any available prey, but prefer ringed seals. They live in the extreme northern latitudes of the planet and face extinction due to global warming and pollution. In the 1770s, initially, two species of polar bear were described. Ursus maritimus is the current accepted classification, and as of 2011, all additional names are considered synonyms.
Subpopulations
Scientists have identified 19 subpopulations of polar bears, though all are the same species. In 2009, studies showed there were between 20,000 and 25,000 polar bears worldwide, but eight of the subspecies were in decline. Subpopulations in the most extreme northern latitudes did not present enough data for a conclusion on their status, so they may well be declining too. Subpopulations around the northern coasts of Alaska and Canada and the Chukohi Sea area of Russia suffered most.
Extinct Polar Bear
During the Pleistocene age, often called the "Ice Age," the first known example of a polar bear appeared. A white mutation of the brown bear, it developed sometime between 100,000 BC and 250,000 BC. The bear stood about 6 feet high at the shoulder, which would rank it as the largest bear known to exist. Since the icy climate stretched far south at the time, its range extended down to England. Its diet is difficult to determine, but most likely it fed on seals the way contemporary polar bears do.
Polar Bear Hybrid
Polar bears and grizzly bears have been known to mate and reproduce in zoos, but DNA evidence of polar bear hybrids in the wild has also surfaced. On April 16, 2006, a hunter shot an apparent polar bear near the southern tip of Banks Island in Canada. However, the bear had spots of brown hair, a concave face and other features of a grizzly. DNA testing concluded the mother was a polar bear and the father, a grizzly. Since mating takes place only after several days of sharing territory closely, it suggests an interesting interspecies dynamic.