Jump to content

Grizzly bear: Difference between revisions

From Wikipedia, the free encyclopedia
Browse history interactively
← Previous editNext edit →
Content deleted Content added
VisualWikitext
Litscot (talk | contribs)
11 edits
Line 25: Line 25:


==Description==
==Description==
Grizzly size and weight varies greatly according to geographic location. Inland bears, particularly those of the Yukon region, may weigh as little as 300 lbs (135 kg) for adult males. The largest populations are found in coastal areas where weights are typically 500-750 lbs (225-340 kg). Populations found in Katmai National Park and the Alaskan Peninsula may approach or just exceed 1000lbs (450 kg), indeed some specimens rival the Kodiak bear in size and weight. The females are on average 38% smaller,<ref name="Bearalmanac">{{cite book |author=Brown, Gary |title=Great Bear Almanac |year=1996 |pages=340 |id=ISBN 1558214747}}</ref> at about 250–450 pounds (114–160&nbsp;kg),<ref>http://www.fws.gov/mountain%2Dprairie/species/mammals/grizzly/</ref> an example of [[sexual dimorphism]]. On average, grizzly bears stand about 1 meter (3.3 ft) at the shoulder when on all fours and 2 meters (6.6 ft) on their hind legs,<ref>http://www.mountainnature.com/wildlife/Bears/BearID.htm</ref> but males often stand 2.44 meters (8 ft) or more on their hind legs. On average, grizzly bears from the Yukon River area are about 20% smaller than typical grizzlies.<ref>[http://www.yesnet.yk.ca/projects/bears/facts/e/grizzly.html The Bear Facts - Types of bears in the Yukon]</ref> Formerly, taxonomists listed brown and grizzly bears as separate species. The Grizzly is classified as a Brown Bear subspecies, Ursus Arctos Horribilis. The term “brown bear” is commonly used to refer to the members of this subspecies found in coastal areas where salmon is the primary food source, but in fact, these are just coastal grizzlies in contemporary taxonomic classification. Inland bears and those found in northern habitats are more often called “grizzlies.” Brown bears on [[Kodiak Island]] are classified as a distinct subspecies from those on the mainland because they are genetically and physically isolated. The shape of their skulls also differs slightly.
Grizzly Bears are usually pink, with yellow stripes. Grizzly size and weight varies greatly according to geographic location. Inland bears, particularly those of the Yukon region, may weigh as little as 300 lbs (135 kg) for adult males. The largest populations are found in coastal areas where weights are typically 500-750 lbs (225-340 kg). Populations found in Katmai National Park and the Alaskan Peninsula may approach or just exceed 1000lbs (450 kg), indeed some specimens rival the Kodiak bear in size and weight. The females are on average 38% smaller,<ref name="Bearalmanac">{{cite book |author=Brown, Gary |title=Great Bear Almanac |year=1996 |pages=340 |id=ISBN 1558214747}}</ref> at about 250–450 pounds (114–160&nbsp;kg),<ref>http://www.fws.gov/mountain%2Dprairie/species/mammals/grizzly/</ref> an example of [[sexual dimorphism]]. On average, grizzly bears stand about 1 meter (3.3 ft) at the shoulder when on all fours and 2 meters (6.6 ft) on their hind legs,<ref>http://www.mountainnature.com/wildlife/Bears/BearID.htm</ref> but males often stand 2.44 meters (8 ft) or more on their hind legs. On average, grizzly bears from the Yukon River area are about 20% smaller than typical grizzlies.<ref>[http://www.yesnet.yk.ca/projects/bears/facts/e/grizzly.html The Bear Facts - Types of bears in the Yukon]</ref> Formerly, taxonomists listed brown and grizzly bears as separate species. The Grizzly is classified as a Brown Bear subspecies, Ursus Arctos Horribilis. The term “brown bear” is commonly used to refer to the members of this subspecies found in coastal areas where salmon is the primary food source, but in fact, these are just coastal grizzlies in contemporary taxonomic classification. Inland bears and those found in northern habitats are more often called “grizzlies.” Brown bears on [[Kodiak Island]] are classified as a distinct subspecies from those on the mainland because they are genetically and physically isolated. The shape of their skulls also differs slightly.
[[Image:Grizzly skull.jpg|thumb|left|200px|A grizzly bear skull]]
[[Image:Grizzly skull.jpg|thumb|left|200px|A grizzly bear skull]]
The grizzly's coloring ranges widely depending on geographic areas, from blond to deep brown, red or even grey. 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 56 kilometres per hour (35 miles per hour). However, they are slower running downhill rather than uphill because of the large hump of muscle over the shoulders. They have very thick fur to keep them warm in brutal, windy, and snowy winters.
The grizzly's coloring ranges widely depending on geographic areas, from blond to deep brown, red or even grey. 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 56 kilometres per hour (35 miles per hour). However, they are slower running downhill rather than uphill because of the large hump of muscle over the shoulders. They have very thick fur to keep them warm in brutal, windy, and snowy winters.

Revision as of 15:53, 6 November 2009

For other uses, see Grizzly bear (disambiguation).

Grizzly Bear
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)
Shrinking distribution during post-glacial, historic and present time

The grizzly bear (Ursus arctos horribilis), also known as the silvertip bear, is a subspecies of brown bear (Ursus arctos) that generally lives in the uplands of western North America. This subspecies is thought to descend from Ussuri Brown Bears which crossed to Alaska 100,000 years ago, though they did not move south until 13,000 years ago.[1]

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

Grizzly Bears are usually pink, with yellow stripes. Grizzly size and weight varies greatly according to geographic location. Inland bears, particularly those of the Yukon region, may weigh as little as 300 lbs (135 kg) for adult males. The largest populations are found in coastal areas where weights are typically 500-750 lbs (225-340 kg). Populations found in Katmai National Park and the Alaskan Peninsula may approach or just exceed 1000lbs (450 kg), indeed some specimens rival the Kodiak bear in size and weight. The females are on average 38% smaller,[2] at about 250–450 pounds (114–160 kg),[3] an example of sexual dimorphism. On average, grizzly bears stand about 1 meter (3.3 ft) at the shoulder when on all fours and 2 meters (6.6 ft) on their hind legs,[4] but males often stand 2.44 meters (8 ft) or more on their hind legs. On average, grizzly bears from the Yukon River area are about 20% smaller than typical grizzlies.[5] Formerly, taxonomists listed brown and grizzly bears as separate species. The Grizzly is classified as a Brown Bear subspecies, Ursus Arctos Horribilis. The term “brown bear” is commonly used to refer to the members of this subspecies found in coastal areas where salmon is the primary food source, but in fact, these are just coastal grizzlies in contemporary taxonomic classification. Inland bears and those found in northern habitats are more often called “grizzlies.” Brown bears on Kodiak Island are classified as a distinct subspecies from those on the mainland because they are genetically and physically isolated. The shape of their skulls also differs slightly.

A grizzly bear skull

The grizzly's coloring ranges widely depending on geographic areas, from blond to deep brown, red or even grey. 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 56 kilometres per hour (35 miles per hour). However, they are slower running downhill rather than uphill because of the large hump of muscle over the shoulders. They have very thick fur to keep them warm in brutal, windy, and snowy winters.

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.[6] 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.[7] They are similar in size, colour and behaviour to the Siberian Brown Bear (Ursus arctos collaris).[8]

Name

The word "grizzly" in its name refers to "grizzled" or grey hairs in its fur, but when naturalist George Ord formally named the bear in 1815 he misunderstood the word as "grisly", to produce its biological Latin specific or subspecific name "horribilis".[9]

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 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.[10] 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 Mexico, European countries, some areas of Canada and in the United States. However, it is expected that its re-population 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].

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.[11]

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, behaviour that can lead them into conflict with other species, such as wolves and humans. A few have been known to eat humans.[12]

The grizzly bears that reside in the American Rocky Mountains are not as large as Canadian or Alaskan grizzlies. 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 behaviour 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.[citation needed]

Interspecific competition

Female grizzly bear in Yellowstone National Park, US

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 grey 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 use 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.[citation needed]

Black bears generally stay out of grizzly territory but grizzlies may occasionally enter their terrain to obtain food sources both bears enjoy, such as pine nuts, acorns, mushrooms, 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.[citation needed]

Polar bears often don't come in contact with grizzlies due to different habitats and diets. However when they do meet, the grizzly is the aggresor, often driving the polar bears off.

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.[citation needed]

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.[citation needed]

Attacks on humans

Grizzlies are considered by some experts to be the most aggressive bears[citation needed] even by the standards of brown bears.[13] 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.[14] Mothers defending cubs are the most prone to attacking, being responsible for 70% of human fatalities.[15] Historically, bears have competed with other large predators for food, which also favors increased aggression.

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 home 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.[citation needed]

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 back-country 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.[16]

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."[17]

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 wiped out in Canada.[18] 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. On September 22, 2009, a federal judge reinstated protection for the bears[19]

Protection

A grizzly in Denali National Park

Within the United States, the U.S. Fish and Wildlife Service concentrates its effort to restore grizzly bears in six recovery areas. These are Northern Continental Divide (Montana), Yellowstone (Montana, Wyoming, and Idaho), Cabinet-Yaak (Montana and Idaho), Selway-Bitterroot (Montana and Idaho), Selkirk (Idaho and Washington), and North Cascades (Washington). The grizzly population in these areas is estimated at 750 in the Northern Continental Divide, 550 in Yellowstone, 40 in the Yaak portion of the Cabinet-Yaak, and 15 in the Cabinet portion (in northwestern Montana), 105 in Selkirk region of Idaho, 10–20 in the North Cascades, and none currently in Selway-Bitterroots, although there have been sightings[20] These are estimates because bears move in and out of these areas, and it is therefore impossible to conduct a precise count. In the recovery areas that adjoin Canada, bears also move back and forth across the international boundary.

The U.S. Fish and Wildlife Service claims that the Cabinet-Yaak and Selkirk areas are linked through British Columbia, a claim that is disputed.[21]

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 the bears scavenge for grain that has leaked from poorly maintained grain cars. Road kills 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 have died within a few hundred meters of roads and trails.[22]

On March 22, 2007, the U.S. 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 a lawsuit against the federal government to re-list the grizzly bear. On September 22, 2009, United States District Judge Donald W. Molloy reinstated the grizzlies' protected status due to the decline of whitebark pine tree, whose nuts are a main source of food for the bears.[19]

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.[22] 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.[23] 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.[24]

Recently the International Union for Conservation of Nature moved the Grizzly bear to "Lower Risk Least Concern" status on the IUCN Red List.[25]

The Mexican Grizzly Bear is extinct.[26]

See also

Notes

  1. ^ McLellan , Bruce and David C . Reiner. 1994. A review of bear evolution. Int. Conf. Bear Res. and Manage. 9(1):85-96.
  2. ^ Brown, Gary (1996). Great Bear Almanac. p. 340. ISBN 1558214747.
  3. ^ http://www.fws.gov/mountain%2Dprairie/species/mammals/grizzly/
  4. ^ http://www.mountainnature.com/wildlife/Bears/BearID.htm
  5. ^ The Bear Facts - Types of bears in the Yukon
  6. ^ Hutchinson's animals of all countries; the living animals of the world in picture and story Vol.I. 1923. p. 384.
  7. ^ Brown bear, Grizzly bear or Kodiak bear?
  8. ^ Brown Bear Hunting in Russia
  9. ^ Wright, William Henry (1909). The Grizzly Bear (1977 ed.). Lincoln, NE: University of Nebraska. pp. 28–29. ISBN 978-0-8032-5865-5.
  10. ^ Grizzly shot in Selway-Bitterroot from the Missoulian website
  11. ^ Grizzly Bear from the Defenders of Wildlife website
  12. ^ http://books.google.com/books?id=gFlz6UKGqrcC&pg=PA51&lpg=PA51&dq=grizzly+bear+devoured+victim&source=bl&ots=algzT0_VKL&sig=KgD1BiVJ9avoLUsCJ2bbbg47mp4&hl=en
  13. ^ Inter-species conflict. Which animal is the ultimate carnivore?
  14. ^ Why are grizzly bears more aggressive than our black bears?
  15. ^ How Dangerous are Black Bears
  16. ^ [1]
  17. ^ Bear Pepper Spray
  18. ^ "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)
  19. ^ a b Lindsay Barnett "Judge renews protected status for Yellowstone's grizzly bears" Los Angeles Times Sep 22, 2009.
  20. ^ Knibb, David, Grizzly Wars: The Public Fight Over the Great Bear pp. 164–213 (Eastern Washington University Press 2008). ISBN 978-1-59766-037-2.
  21. ^ Knibb, David, Grizzly Wars: The Public Fight Over the Great Bear pp. 202–04 (Eastern Washington University Press 2008). ISBN 978-1-59766-037-2.
  22. ^ a b "Wildlife Status - Grizzly bear - Population size and trends". Fish and Wildlife Division of Alberta Sustainable Resource Development. Retrieved 2008-04-06.
  23. ^ 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)
  24. ^ "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)
  25. ^ 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)
  26. ^ 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.
Retrieved from "https://en.wikipedia.org/enwiki/w/index.php?title=Grizzly_bear&oldid=324291860"