grizzly bear

The Grizzly Bear, sometimes called the Silvertip Bear, is a powerful brownish-yellow bear that lives in the uplands of western North America. It has traditionally been treated as a subspecies, Ursus arctos horribilis, of the brown bear living in North America.

Grizzly Bears reach weights of 180–680 kg (400–1,500 lb); the male is on average 1.8 times as heavy as the female, an example of sexual dimorphism. Their coloring ranges widely across geographic areas, from blond to deep brown or black. These differences, once attributed to subspeciation, are now thought to be primarily due to the different environments these bears inhabit, particularly with regard to diet and temperature.

The Grizzly has a large hump over the shoulders which is a muscle mass used to power the forelimbs in digging. The head is large and round with a concave facial profile. In spite of their massive size, these bears can run at speeds of up to 55 km/h (35 mph).

Normally a solitary, nocturnally active animal, in coastal areas the Grizzly congregates alongside streams and rivers during the salmon spawn. Every other year females (called sows) produce one to four young (most commonly two) which are small and weigh only about 500 g (1 pound). Sows are very protective of their offspring.

The current range of the Grizzly Bear extends from Alaska, south through much of Western Canada, and into the northern Northwestern United States including Idaho, Montana and Wyoming. Its original range also included much of western and southern United States, but it has been extirpated in those areas. It is expected that the grizzly's repopulation of its U.S. range will be a slow process due equally to the ramifications of reintroducing such a large animal to areas which are prized for agriculture and livestock and also because of the bear's slow reproductive habits (Bears invest a good deal of time in raising young).

Diet

Being omnivores, grizzlies feed on a variety of plants and berries including roots or sprouts and fungi, as well as insects and smaller mammals; what is eaten depends largely on time of year and precise location. The larger bears have been known to prey on large mammals such as moose, sheep, and caribou. Grizzly bears in general will feed on fish like salmon, trout, and bass, but those with access to a more protein-enriched diet in coastal areas can grow much larger than their herbivorous cousins.

In preparation for winter, bears will gain hundreds of kilograms of fat before going into a state of false hibernation. There is some debate amongst professionals as to whether or not Grizzly Bears technically hibernate. Much of this debate revolves around body temperature and the ability for the bears to move around during hibernation on occasion. One interesting adaptation is that Grizzly Bears have the ability to partially recycle their body wastes during this period. In some areas where food is plentiful all year round, Grizzly Bears will forego hibernation altogether.

Legal status

The Grizzly Bear is listed as threatened in the contiguous United States, and endangered in parts of Canada. It is currently rapidly repopulating areas where it was previously extirpated. On January 9, 2006, the US Fish and Wildlife service proposed to remove Yellowstone grizzlies from the list of threatened and protected species.

Some biologists have argued that the word horribilis should be removed from the bear's taxonomic name, as its negative connotations may hinder conservation efforts. This change would not be permitted by the International Code of Zoological Nomenclature.

Trivia

• In April 2006, the first grizzly-polar bear hybrid found in the wild was discovered at Banks Island, Canada.

• The Grizzly Bear was the first real-world animal to appear in the Nickelodeon TV Show Avatar the last airbender

See also

• List of fatal bear attacks in North America by decade