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Grizzly Bear (Ursus arctos horribilis) - Wiki
| Subject: | Grizzly Bear (Ursus arctos horribilis) - Wiki
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Grizzly bear
From Wikipedia, the free encyclopedia
[Photo] Brown bears at Brooks Falls Katmai National ParkPhotograped by Mila Zinkova (http://home.comcast.net/~milazinkova/Fogshadow.html) in July of 1998. The picture is a digital picture of an old film picture.
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 kilograms (400???1,500 pounds) and stand 2.44 m (8 feet) tall on its hind legs.; the male is on average 1.8 times as heavy as the female, an example of sexual dimorphism. This dimorphism suggests that size is an important factor in the male's ability to successfully compete for and attract breeding opportunities. 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 fifty-five kilometers per hour (thirty-five miles per hour).
Normally a solitary active animal, in coastal areas the grizzly congregates alongside streams and rivers during the salmon spawn. Every other year females (sows) produce one to four young (most commonly two) which are small and weigh only about 500 grams (one 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 portions of the Northwestern United States including Idaho, Montana, Washington and Wyoming, extending as far south as Yellowstone and Grand Teton National Parks, but is most commonly found in Canada. It is argued by some that there still remains a small population in Southern Colorado in the Southern San Juan Mountains. Its original range also included much of the Great Plains and the Southwestern states, but it has been extirpated in most of those areas. The grizzly currently enjoys legal protection in the United States. However, it is expected that its repopulation of its former 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 to the bear's slow reproductive habits (bears invest a good deal of time in raising young). There are currently about 60,000 wild grizzly bears currently located throughout North America. Brown bears (of which the grizzly bear is a subspecies) can live up to thirty years in the wild, though twenty to twenty-five is normal.
Diet
Bears have been known to prey on large mammals such as moose, deer, sheep, caribou and even black bears. Grizzly bears will feed on fish such as salmon, trout, and bass, and those with access to a more protein-enriched diet in coastal areas potentially grow larger than interior individuals. Grizzly bears will readily scavenge food, behavior that can lead them into conflict with other species, such as wolves and humans.
The grizzly bears that reside in the American northwest are not as large as Canadian or Alaskan sub-species Ursus arctos. This is due, in part, to the richness of their diet which in Yellowstone consists of whitebark pine nuts, roots, tubers, grasses, various rodents, army cutworm moths and scavenged carcasses, none of which match the fat content of the salmon available in Alaska and British Columbia. During early spring, as the bears emerge from their dens, elk and bison calves are actively sought. The bear will move in a zig-zag pattern, nose to the ground, hoping to find a meal.
In preparation for winter, bears will gain hundreds of kilograms of fat, during a period of hyperphagia, before going into a state of false hibernation. The bear will often wait for a substantial snowstorm before it enters its den. Presumably, this behavior lessens the chances that predators will be able to locate the den. The dens themselves are typically located at elevations above 6,000 feet on northern-facing slopes. There is some debate amongst professionals as to whether grizzly bears technically hibernate. Much of the debate revolves around body temperature and the ability of the bears to move around during hibernation on occasion. Grizzly bears have the ability to "partially" recycle their body wastes during this period. In some areas where food is plentiful year round, grizzly bears forgo hibernation altogether.
Interspecies competition
Most notable in Yellowstone have been the interactions between gray wolves and grizzly bears. Since the reintroduction of gray wolves to Yellowstone, many lucky visitors have witnessed a once common struggle between a keystone species, the grizzly bear, and its historic rival, the gray wolf. The interactions of U. arctos horribilis with the wolves of Yellowstone have been under considerable study. Typically, the conflict will be over a carcass, which is commonly an elk killed by wolves. The grizzly bear will use its strong sense of smell to locate the kill first. Then the wolves and grizzly will play a game of cat and mouse. One wolf may try to distract the bear while the others feed. The bear then may retaliate by chasing the wolves. If the wolves become aggressive with the bear it is normally in the form of careful nips at its hind legs. Thus, the bear will sit down and ease its ability to protect itself in a full circle. Rarely do interactions such as these end in death or serious injury to either animal. One carcass simply isn't usually worth the risk to the wolves if the bear has the upper hand (due to strength and size) or to the bear (if the wolves are too numerous or persistent). Over time, it seems the grizzly bears have benefited from the presence of the gray wolf because of increased food availability.
Legal status
The grizzly bear is listed as threatened in the contiguous United States, and endangered in parts of Canada. In May 2002, the Canadian Species at Risk Act listed the Prairie population (Alberta, Saskatchewan and Manitoba range) of grizzly bears as being extirpated in Canada. In Alaska and parts of Canada however, the grizzly is still legally shot for sport by hunters. 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.
Protection
Many national parks, such as Yellowstone and Grand Teton, have laws and regulations in place to protect the bears.
On March 22, 2007, The US Federal Government stated that Grizzly bears in and around Yellowstone National Park no longer need Endangered Species Act protection. Several environmental organizations including the NRDC have since brought legal suit against the federal government to relist the grizzly bear.
Environment Canada consider the Grizzly bear to a "special concern" species, as it is particularly sensitive to human activities and natural threats. In Alberta and British Columbia, the species is considered to be at risk.
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http://en.wikipedia.org/wiki/Grizzly_bear
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Scientific Name: Ursus arctos horribilis Ord, 1815
Common Names: Grizzly Bear, North American Brown Bear, Silvertip Bear |
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