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In preparation for winter, bears gain hundreds of kilograms of fat, during a period of [[hyperphagia]], before going into a state of [[hibernation|false hibernation]]. The bear often waits for a substantial snowstorm before it enters its den, such behavior lessening 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 skip hibernation altogether.
In preparation for winter, bears gain hundreds of kilograms of fat, during a period of [[hyperphagia]], before going into a state of [[hibernation|false hibernation]]. The bear often waits for a substantial snowstorm before it enters its den, such behavior lessening 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 skip hibernation altogether.


they eat lions. i know this cuz im the goodest reasercher evers.
==Interspecies competition==
[[Image:Grizzly Bear Yellowstone.jpg|right|thumb|Female grizzly bear in Yellowstone National Park, U.S.A.]]Most notable in Yellowstone have been the interactions between [[gray wolves]] and grizzly bears. Since the reintroduction of gray wolves to Yellowstone, many 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 uses its keen sense of smell to locate the kill. 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 quick 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.

Black bears generally stay out of grizzly territory but the grizzly may occasionally enter black bear terrain to obtain food sources both bears enjoy, such as pine nuts, acorns, and berries. When a black bear sees a grizzly coming it either turns tail and runs or climbs a tree. Black bears are not strong competition for prey because they have a more herbivorous diet. Confrontations are rare because of the difference in size, habitat, and diet of the bear species. When this happens it is usually with the grizzly being the aggressor. The black bear will only fight when it is a smaller grizzly such as a yearling or when the black bear has no other choice but to defend itself. This usually results in the black bear's death.

[[Cougars]] however, generally give the bears a wide berth. Grizzlies have less competition with cougars than with other predators such as coyotes, wolves, and other bears. When a grizzly descends on a cougar feeding on its kill, the cougar usually gives way to the bear. When a cougar does stand its ground, the cougar will use its superior agility and its claws to harass the bear yet stay out of its reach until one of them gives up, usually the cat.

[[Coyotes]], foxes, and wolverines are generally regarded as pests to the grizzlies rather than competition, though coyotes and wolverines may compete for smaller prey such as rabbits and deer. All three will try to scavenge whatever they can from the bears. Wolverines are aggressive enough to occasionally persist until the bear ambles on, leaving more than normal scraps for the smaller animal.


==Attacks on humans==
==Attacks on humans==

Revision as of 14:50, 8 February 2009

For other uses, see Grizzly bear (disambiguation).

Grizzly Bear
Ursus arctos horribilis
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Mammalia
Order:
Carnivora
Family:
Ursidae
Genus:
Ursus
Species:
U. arctos
Subspecies:
U. a. horribilis
Trinomial name
Ursus arctos horribilis
(Ord, 1815)
Current range of Ursus arctos horribilis in purple, historic range in pink.

The Grizzly Bear (Ursus arctos horribilis), also known as the Silvertip Bear, is a subspecies of brown bear (Ursus arctos) that lives in the uplands of western North America.

Grizzlies are normally solitary active animals, but in coastal areas the grizzly congregates alongside streams, lakes, rivers, and ponds during the salmon spawn. Every other year, females (sows) produce one to four young (commonly two) which are small and weigh only about 500 grams (one pound). A sow is protective of her offspring and will attack if she thinks she or her cubs are threatened.

Description

Male grizzly bears can reach and stand 3 meters (10 ft) tall on their hind legs; the females are on average 38% smaller,[1] an example of sexual dimorphism. Their coloring ranges widely across geographic areas, from blonde to deep brown or red. The grizzly has a large hump over the shoulders, which is a muscle mass used to power the forelimbs in digging. The hind legs are more powerful, however. The muscles in the lower legs provide enough strength for the bear to stand up and even walk short distances on its hind legs, giving it a better view of its surroundings. 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 64 kilometers per hour (40 miles per hour). However, they are slower running downhill rather than uphill because of the large hump of muscle over the shoulders.

A grizzly bear skull

Grizzlies can be distinguished from most other brown bear subspecies by their proportionately longer claws and cranial profile which resembles that of the polar bear.[2] Compared to other North American brown bear subspecies, a grizzly has a silver tipped pelt and is smaller in size. This size difference is due to the lesser availability of food in the grizzlies' landlocked habitats.[3] They are similar in size, color and behavior to the Siberian Brown Bear (Ursus arctos collaris).[4]

Range

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. There may still be a small population in southern Colorado in the southern San Juan Mountains. In September 2007 a hunter produced evidence of grizzly rehabilitation in the Selway-Bitterroot ecosystem by killing a male grizzly.[5] 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, Canada, Mexico, and European countries. 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 located throughout North America.[citation needed] These bears weigh from 400 to 600 pounds.

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.[6]


Diet

A mother grizzly with a cub

Although grizzlies are of the order Carnivora and have the digestive system of a carnivore, they are actually omnivores since their diet consists of both plants and animals. They have been known to prey on large mammals such as moose, deer, sheep, elk, bison, caribou and even black bears. Grizzly bears 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 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. This is due, in part, to the richness of their diet which in Yellowstone consists of whitebark pine 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 moves in a zig-zag pattern, nose to the ground, hoping to find unsuspecting animals to feed on.

In preparation for winter, bears gain hundreds of kilograms of fat, during a period of hyperphagia, before going into a state of false hibernation. The bear often waits for a substantial snowstorm before it enters its den, such behavior lessening 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 skip hibernation altogether.

they eat lions. i know this cuz im the goodest reasercher evers.

Attacks on humans

Grizzlies are considered by some experts to be the most aggressive bears, even by the standards of brown bears.[7] Aggressive behavior in grizzly bears is favored by numerous selection variables. Unlike the smaller black bears, adult grizzlies are too large to escape danger by climbing trees, so they respond to danger by standing their ground and warding off their attackers. Increased aggressiveness also assists female grizzlies in better ensuring the survival of their young to reproductive age.[8] Mothers defending cubs are the most prone to attacking, being responsible for 70% of grizzly caused human fatalities.[9] Historically, bears have competed with other large predators for food, which also favors increased aggression.

Precautionary measures

Campers are warned to hang food, garbage, and toiletries out of reach of bears, or to use a secure bear cache

Grizzly bears normally avoid contact with people. In spite of their obvious physical advantages and many opportunities, they almost never view humans as prey. Even so, they can be extremely dangerous animals. Most grizzly bear attacks result from a bear that has been surprised at very close range, especially if it has a supply of food to protect, or female grizzlies protecting their offspring. In recent years, some grizzly bears appear to have learned to hone in on the sound of hunters' gunshots in late fall as a source of potential food, and inattentive hunters have been attacked by bears trying to appropriate their kills.

It is imperative for all campers in areas inhabited by grizzly to maintain a clean campsite. Reports have indicated that something as innocuous as a tube of lip balm can entice a bear to come near a campsite in search of food. Any bear that is conditioned to finding food around campsites will almost always return and expect the same reward. The bear is then a threat to campers and itself, and park rangers may be forced to kill it. For backcountry campers, hanging food between trees at a height unreachable to bears is a common procedure, although some grizzlies can climb and reach hanging food in other ways. An alternative to hanging food is to use a bear canister.

Since most grizzlies prefer to avoid people, it is a good idea to make noise when traveling in dense brush or other places where visibility is limited. High pitched shouts or whistles will alert nearby bears and give them a chance to get out of the way. "Bear bells" are generally useless as their sound does not travel far.

The Sierra Club wants the Forest Service to require everyone who enters a national forest in grizzly bear country to carry bear spray. Spokeswoman Heidi Godwin said in a news release: "The proper use of bear pepper spray will reduce human injuries caused by bears, reduce the number of grizzly bears killed in self defense, and help promote the recovery and survival of the grizzly bear." [10]

Pepper-based bear sprays (containing at least 1% of the active ingredient capsaicin) have proven effective in deterring bears[citation needed], both grizzly and black[citation needed], that attacked after being surprised at close range.[citation needed] The spray causes instant irritation of exposed mucous membranes in the eyes, nose and mouth, and in the great majority of cases where it has been used, immediately diverts the bear.[citation needed]Whilst just the surprise of a sharp spray can deter the bear, this cannot be counted on. Combined with most people's inexperience with firearms, the practicality of the firearm at hand, where to hit a bear if possessing one, and the suddenness of the situation, recent research has shown that bear spray is significantly more effective than firearms.[citation needed] A further advantage of bear spray is that it leaves the bear alive and perhaps less likely to attack in the future. However, bear spray is far from guaranteed, as a bear will either ignore it [3], or as in attacks on groups of two or more, the bear will sometimes simply move on to the next person[11]. Also, if the can is not 100% full or reaches its expiration date, it may prove ineffective[12].

In the event of a surprise attack that cannot be repelled, it is important not to make eye contact with the bear as eye contact can be seen as aggression. Adopt a submissive posture and remain still; often a charging grizzly will turn away at the last moment. Never run from a bear—uphill, downhill or into water. Grizzlies can outrun humans. Some say that climbing a tree can be a good defense, if there is time, as the long curved digging claws of a grizzly makes it hard for the bear to grip a tree and climb it. [citation needed] Others[who?] argue that climbing trees is not a good idea since many bears can and will climb up after you. [citation needed] If you do take to a tree, you should get at least two to three times as high as the bear can reach.[citation needed]

Where grizzlies do follow through on a charge and actually attack, they will usually bite at the head. The best defense is to lie prone, face down, legs spread to make it harder for the bear to flip you over, and hands gripped around the neck. Normally, once a grizzly is sure you are no longer a threat, it will leave.[citation needed] This is why most wildlife agencies in grizzly country advise that people play dead if attacked. Struggling or fighting back will almost certainly intensify and prolong the attack[citation needed]; at the same there is advice to actually fight back.[citation needed]

Grizzlies are driven by the need to find high-calorie food, especially first thing in the spring after hibernation and from late August through to their hibernation season in November. For this reason, people who live in bear country or camp, hunt or hike there, are well-advised to ensure that nothing that might smell edible to a bear is left exposed, especially overnight. Food and garbage should be locked securely in a hard-bodied structure or double-wrapped in plastic bags and suspended from a line at least 10 feet from the ground in campsites.

When traveling in grizzly territory, hikers should be aware of their surroundings at all times, recognizing the signs of bear presence in the area. Fresh diggings can indicate a grizzly recently feeding on vegetation or hunting rodents. A grizzly track is unlike that of a black bear in that one can trace a single line from the innermost point on the left toe to the innermost point on the right toe without intersecting the pad of the foot. Claws are normally more than an inch from the end of the toe. Other signs include: talus slopes that appear raked, fallen logs which have been torn up, and high claw marks on trees. The smell of decomposing flesh is a danger sign, as bears will take possession of animal carcasses and defend these rich food supplies aggressively; hikers should always give a wide berth to any area where there is a strong odour.

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[13]. 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. In March 2007, the U.S. Fish and Wildlife Service "de-listed"the population, effectively removing Endangered Species Act protections for grizzlies in the Yellowstone National Park area.

Protection

All national parks, such as Banff National Park, Yellowstone and Grand Teton, and Theodore Roosevelt National Park have laws and regulations in place to protect the bears. Even so, grizzlies are not always safe in parks. In Glacier National Park in Montana and Banff National Park in Alberta, grizzlies are regularly killed by trains as they scavenge for grain that has leaked from poorly maintained grain cars. Roadkills on park roads are another problem. The primary limiting factors for grizzly bears in Alberta and elsewhere are human-caused mortality, unmitigated road access, and habitat loss, alienation and fragmentation. In the Central Rocky Mountains Ecosystem most bears died within a few hundred metres of roads and trails.[14]

On March 22, 2007, The U.S. Federal Government stated that Grizzly bears in and around Yellowstone National Park (Greater Yellowstone Ecosystem) 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.

Farther north, in Alberta, Canada, intense DNA hair-snagging studies on 2000 showed the grizzly population to be increasing faster than what it was formerly believed to be, and Alberta Sustainable Resource Development calculated a population of 841 bears.[14] In 2002, the Endangered Species Conservation Committee recommended that the Alberta grizzly bear population be designated as Threatened due to recent estimates of grizzly bear mortality rates that indicated that the population was in decline. A recovery plan released by the Provincial government in March 2008 indicates that the grizzly population is lower than previously believed.[15] The Provincial government has so far resisted efforts to designate its declining population of about 700 grizzlies (previously estimated at as high as 842) as endangered.[citation needed]

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.[16]

Recently the International Union for Conservation of Nature moved the Grizzly bear to "Lower Risk Least Concern" status on the IUCN Red List.[17]

The Mexican Grizzly bear is extinct.[18]

Reintroduction in North America

Grizzly bears engaged in a play fight at San Francisco Zoo

Historic range

The present range of grizzly bears in the United States has significantly decreased within the past 200 years.[citation needed] In the mid 1800s, populations were distributed throughout the western United States including all of[Montana, Wyoming, and Colorado, and most of Idaho, Washington, Oregon, California, Arizona, Alaska, New Mexico, Utah, North Dakota and South Dakota, and parts of Nebraska, Kansas, Nevada, Oklahoma, and Texas.[citation needed] The following is a table of reported Grizzly Bear populations in Canadian jurisdictions from 1991 to 2001/2002:

Population estimates by jurisdiction[citation needed]
1991 2001-2002
Alberta 575 to 660 750 to 841
BC 1,300 to 1,340 1,375 to 1,400
Yukon 6,300 to 6,300 6,300 to 6,350
NWT 5,050 to 5,065 5,080 to 5,100
Nunavut 900 950 to 1,000
Alb.nat. 205 to 215 185 to 193
Totals 14,330 to 14,480 14,640 to 14,884

Human threat of extinction

The primary explanation for the range and population decreases of grizzly bears in North America has been anthropogenic. With the gold rush beginning in the late 1840s, people began to establish settlements throughout the indigenous ranges of the grizzly bear. People killed the bears for their meat, fur, and because they were seen as a threat to humans. Additional contact between bears and settlers increased with western expansion, which led to a rapid decline in grizzly bear populations. By 1870, grizzly bears were scarce, even in the state of California where they were once plentiful.

Rewilding

The ideas of rewilding and reintroducing species to their natural environment are concepts based in conservation biology with the purpose of recovering lost biodiversity. Grizzly bears are just one of many species that have been diminished by the activities of humans, and reintroducing them to wilderness areas inside their historic ranges is a significant step in improving the natural biodiversity within the United States.


Ecological effects

The reintroduction of grizzly bears in habitats where they have naturally lived in the past has many positive effects on the surrounding ecosystem. As terrestrial predators, grizzly bears indirectly influence their ecological community from the top-down, causing a cascade effect which impacts the trophic levels within the community structure, and other organisms within the area. In the absence of grizzly bears, ungulate populations can increase beyond natural levels, dramatically altering vegetation structure and decreasing avian species richness, which both vary inversely with ungulate abundance. Grizzly bears also directly influence plant communities through digging habits. As they dig and forage for selective vegetation, grizzly bears disturb the nutrient structure in the soil which increases the available ammonium and nitrate levels for other plant species. In these ways, grizzly bears can increase the natural diversity of their habitat and help bring the ecosystem dynamics closer to a stable equilibrium.

Social effects

Communities of farmers and people who live adjacent to designated grizzly bear reintroduction reserves will be more susceptible to bear attacks and property damage. This is one of the main problems with reintroduction practices. People can feel threatened by animals such as the grizzly bear appearing in their neighborhoods. This may lead to protests against the implementation of the reintroduction project. Therefore, the chosen wilderness area must be as remote as possible in order to limit grizzly bear encounters with human populations and prevent the occurrence of any negative social impacts.

Steps involved

When an adequate wilderness area of historical grizzly bear range is selected for the reintroduction, grizzly bears must be transported from one of the remaining populations within North America. Existing historical samples of preserved skin from grizzly bears who previously lived in the chosen area can be analyzed for their DNA properties. DNA samples from the remaining grizzly bear populations in North America can then be compared to the historical samples in order to determine the best possible match. The DNA analysis will provide the most precise method for selecting grizzly bears from populations that will have the highest probability of survival in the selected area of reintroduction.

Minimum viable populations

After a site is chosen for reintroduction, the number of grizzly bears released into the area must be large enough for the population to survive in the long run. A minimum number of 200-250 grizzly bears on a reserve ranging from 8,556 to 17,843 square kilometers (3,303 to 6,889 mi²) is required for a low probability of species decline and an average extinction time greater than 20 years. A smaller group of individuals will result in a certain population decline or extinction and reintroduction efforts will result in failure.

See also

Notes

  1. ^ Brown, Gary (1996). Great Bear Almanac. pp. pp.340. ISBN 1558214747. {{cite book}}: |pages= has extra text (help)
  2. ^ Hutchinson's animals of all countries; the living animals of the world in picture and story Vol.I. 1923. pp. pp.384. {{cite book}}: |pages= has extra text (help)
  3. ^ Brown bear, Grizzly bear or Kodiak bear?
  4. ^ Brown Bear Hunting in Russia
  5. ^ Grizzly shot in Selway-Bitterroot from the Missoulian website
  6. ^ Grizzly Bear from the Defenders of Wildlife website
  7. ^ Interspecies conflict. Which animal is the ultimate carnivore?
  8. ^ Why are grizzly bears more aggressive than our black bears?
  9. ^ How Dangerous are Black Bears
  10. ^ Bear Pepper Spray
  11. ^ [1]
  12. ^ [2]
  13. ^ "Species at Risk - Grizzly Bear Prairie population". Environment Canada. 2006-05-08. Retrieved 2008-04-08. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  14. ^ a b "Wildlife Status - Grizzly bear - Population size and trends". Fish and Wildlife Division of Alberta Sustainable Resource Development. Retrieved 2008-04-06.
  15. ^ Alberta Grizzly Bear Recovery Team. "Alberta Grizzly Bear Recovery Plan 2008-2013, Alberta Species at Risk Recovery Plan No. 15" (PDF). Retrieved 2008-04-06. {{cite web}}: line feed character in |title= at position 21 (help)
  16. ^ "Species at Risk - Grizzly Bear Northwestern population". Environment Canada. 2006-05-08. Retrieved 2008-04-06. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  17. ^ Bear Specialist Group 1996. "Ursus arctos. In: IUCN 2007. 2007 IUCN Red List of Threatened Species". Retrieved 2008-04-09.{{cite web}}: CS1 maint: numeric names: authors list (link)
  18. ^ Bear Specialist Group 1996. "Ursus arctos ssp. nelsoni. In: IUCN 2007. 2007 IUCN Red List of Threatened Species". Retrieved 2008-04-09.{{cite web}}: CS1 maint: numeric names: authors list (link)

References

Wikimedia Commons has media related to Ursus arctos horribilis.
Wikispecies has information related to Ursus arctos horribilis.
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