Grizzly Bear

views updated Jun 11 2018

Grizzly Bear

Ursus arctos horribilis

ListedMarch 11, 1967
FamilyUrsidae (Bears)
DescriptionLarge brown bear with humped shoulder and long, curved front claws.
ReproductionUsually 2 cubs every 3-4 years.
ThreatsLogging, recreational use of habitat, poaching.
RangeColorado, Idaho, Montana, Washington, Wyoming


The brown bear or grizzly, as it is more commonly known, Ursus arctos horribilis, is one of the largest and most menacing of North American land mammals. It is characterized by a humped shoulder, a long snout, a somewhat concave face, and long, curved front claws. Adult males range in size from 300-850 lbs (135-385 kg) and reach a shoulder height of 4.5 ft (1.4 m) when on all fours. When standing on its hind legs, as it often does to survey the landscape, the male may reach an imposing 9 ft (2.7 m) tall. Females are slightly or considerably smaller. The grizzly's color varies widely from brown to nearly black, but in mature animals, the long hairs on the back are lighter at the tips, giving the animal a silvery appearance, hence the name "grizzly." The grizzly can live more than 30 years.


The grizzly bear is adapted for great strength, agility, and speed. An omnivorous and opportunistic feeder, it feeds primarily on green vegetation, pine nuts and berries, and roots and tubers. The bulk of the meat in its diet is carrion, although bears in some areas prey upon deer and other small mammals. Bears along the coast use salmon as their main food source. Bears hibernate through the winter and, when they emerge from their dens in the spring, must seek out food sources high in protein.

The grizzly's home range is among the largest of the land mammals. Particularly active individuals may range over an area of 800-1,000 sq mi (2,070-2,590 sq km). The grizzly migrates to lower elevations in spring and fall and returns to higher elevations in midsummer for denning and in winter for hibernation. It defends only its breeding territory, which is restricted to the immediate area around its den. Mothers jealously guard cubs and may enforce a distance of several hundred yards with fury, chasing off intruders.

Bears are solitary animals except when breeding or caring for young. Mating season is from May through July, peaking in mid-June. Females in heat (estrus may last from a few days to more than one month) are receptive to practically all adult males, and both sexes are normally promiscuous. Females reach sexual maturity after about four years, and the average interval between births is three and one-half years. The gestation period is between 229 and 266 days; litter sizes range from one to three, averaging two cubs. Cubs emerge from hibernation with the mother in spring and stay with her for up to two years while they learn to hunt and forage.

A grizzly bear typically digs its own hibernation den, usually into the side of a steep, northern slope where snow accumulates; the snow provides good insulation throughout the winter. Bears occasionally use natural caves for hibernating.


Ideal habitat conditions for grizzlies are found in undisturbed wilderness forests that are interspersed with moist meadows and grasslands. Most remaining habitat is ruggedly mountainous, ranging in elevation between 5,000-10,000 ft (1,500-3,000 m). The grizzly ventures briefly into open areas to forage but is seldom seen far from cover.


Before human settlement, the grizzly bear ranged throughout North America from the Rocky Mountains westward and from central Mexico north throughout Alaska, wherever suitable habitat was present. The steady loss of pristine wilderness lands in the lower 48 states has forced the grizzly bear into more northerly pockets of mountainous wilderness. The relatively abundant Alaskan population is not considered in jeopardy. The grizzly was extirpated from Texas by the turn of the century, from California and most of Utah in the 1920s, and from Oregon, New Mexico, and Arizona in the 1930s. A grizzly killed in the San Juan Mountains of Colorado in 1979 may have been one of the last animals in that state.

As a result of human activities, number of bears plummeted from historical levels of 50,000 to 100,000 bears down to fewer than 1,000 by 1975 in the conterminous United States. Today, remnant populations of grizzlies are confined to isolated fragments of habitat that comprise 2% of their original range. In 1994, it was estimated that fewer than 1,000 grizzly bears occurred in the United States, excluding Alaska.

In the lower 48 states where it is classified as Threatened, the grizzly bear is restricted to five isolated ecosystems in the northwestern states: the Yellowstone Ecosystem in Wyoming, Montana, and Idaho; the Northern Continental Divide Ecosystem in Montana; the Cabinet-Yaak Ecosystem in Montana and Idaho; the Selkirk Mountains Ecosystem in Idaho and Washington; and the North Cascades Ecosystem in Washington. Additionally, bears may occur in the Bitterroot Ecosystem in Idaho and Montana (comprising the largest contiguous wilderness in the lower 48 states), and in the San Juan Mountains of Colorado, though as of 1994, no substantive evidence of grizzly bears existed for those areas, despite some reports of sightings over the years.

The Yellowstone Ecosystem includes Yellowstone and Grand Teton national parks and portions of the Shoshone, Bridger-Teton, Targhee, Gallatin and Custer national forests-areas totaling 5.5 million acres (2.2 million hectares). Some 55,000 acres (22,260 hectares) of adjacent state and private lands in Montana, Wyoming, and Idaho are included in this figure. In 1988, the grizzly bear population for this ecosystem was estimated at between 170 and 180 and was thought to be increasing at a rate of about two animals per year, the first increases noted since 1975. In 1994, minimum population estimate for the ecosystem was 236 bears, with the annual average number of females with cubs at 9.8.

The Northern Continental Divide Grizzly Bear Ecosystem contains 5.7 million acres (2.3 million hectares) of occupied grizzly bear habitat. This Montana area includes Glacier National Park, parts of the Flathead and Blackfoot Indian Reservations, and portions of five national forests (Flathead, Helena, Kootenai, Lewis and Clark, and Lolo). The 1985 population was thought to be between 440 and 680 bears, about one bear per 8 sq mi (21 sq km). In spite of uncertainty about the status of the bear population, some sport hunting of grizzlies is allowed each year by the state of Montana. In 1994, the minimum estimated bear population for the ecosystem was 306 bears (the largest grouping), with an annual average number of females with cubs estimated at 11.3 inside Glacier National Park, and 13.3 outside the park.

The Cabinet-Yaak Ecosystem along the Montana-Idaho border consists of more than one million acres (405,000 hectares) and includes the Cabinet Mountain Wilderness, Northwest Peaks, and the Yaak River Valley. Only about a dozen bears were known to inhabit the Cabinet Mountains in 1985, and the status of grizzlies in other parts of the ecosystem is unknown. The 1994 minimum population estimate for the ecosystem was 15 bears. Nine grizzlies were radio-collared between 1986 and 1993 and reproduction was documented.

The Selkirk Mountains Ecosystem of northeastern Washington and northwestern Idaho is not well defined. A portion of the Kaniksu National Forest in extreme northern Idaho and adjacent lands in the Colville National Forest in Washington have been identified by state and Forest Service biologists as occupied by grizzly bears. A Canadian population adjoins this area, and an inter-migration of animals between these populations is likely. The 1994 minimum grizzly bear population estimates for the Selkirks was 25 bears. As of 1993, 28 grizzlies had been radio-collared for monitoring.

Washington's North Cascades Ecosystem includes North Cascades National Park and adjacent portions of the Mount Baker and Snoqualmie, Okanogan, and Wenatchee national forests. The range extends north into British Columbia, but the size of the grizzly population is unknown; though grizzly bears were known there as recently as 1975, no substantive evidence exists that the bears are still present in the ecosystem.

About 95% of the grizzly bear's current habitat in the lower 48 states is on federal and state lands, including a portion on Native American lands under jurisdiction of the Bureau of Indian Affairs. Federal lands fall under the authority of the Forest Service, the Park Service, and Bureau of Land Management (BLM), and are managed as wilderness or as multiple-use lands.


Because of its wide range and aversion to prolonged human contact, the presence of a stable population of grizzly bears is indicative of healthy, intact wilderness ecosystems. The grizzly bear population can be used as a yardstick to determine whether or not the United States' established policy of maintaining viable wilderness areas in the lower 48 states is being met. Currently, wilderness goals could be considered threatened along with the grizzly bear.

The Forest Service and the BLM permit considerable commercial timber harvesting on public lands each year. The effect of these activities on grizzly behavior and habitat are not sufficiently understood but are probably considerable. In addition, activities in wilderness areas related to oil and mineral exploration have been stepped up, intensifying human intrusion into remaining tracts of pristine wilderness.

Recreational visitors to the major national parks and forests within the grizzly's range have increased significantly in recent years. In addition, residential development on private lands adjacent to public lands has increased, bringing humans and grizzlies into closer contact. Bears are sometimes attracted to garbage at camping sites and residential areas. These bears damage property and threaten pets and livestock but, for the most part, are merely considered a nuisance. Occasionally, a bear that is overly aggressive and too accustomed to human contact loses its instinctive fear and becomes a real danger to human life. The Endangered Species Act protects grizzlies from hunting on federal lands; however, a provision does allow problem bears to be killed in defense of human life. Some illegal poaching still occurs in spite of strong federal and state penalties. Poachers often claim that they killed in self defense after being attacked.

Because of the sometimes conflicting goals of preserving wilderness and allowing citizens access to wilderness, national parks and forests provide an environment that is conducive to conflicts between humans and grizzly bears. But there are numerous examples of humans and grizzly bears coexisting compatibly. Ranchers, loggers, wildlife professionals, and many others spend a lot of time within bear habitats with relatively few problems. On the whole, these people are aware of bear behavior and display a healthy caution. They move predictably and loudly through suspected bear habitat. Casual visitors to the wilderness are less cautious and occasionally surprise a foraging bear or stumble upon a mother and her cubs. When surprised or when defending cubs, the grizzly may attack with unfortunate results.

Conservation and Recovery

The U.S. Fish and Wildlife Service (FWS) 1982 Recovery Plan for the grizzly bear outlines a three-pronged strategy for management efforts: maintaining suitable habitat, limiting human-caused mortality, and minimizing bear and human contacts. Because the status of most bear populations is poorly understood, the FWS has placed a high priority on developing a population-monitoring system that can determine trends as well as size. To this end, some animals have been tagged and fitted with radio transmitters, and, beginning in 1982, annual aerial surveys were instituted. Ground survey techniques are being standardized so that data from different sites can be compared. More extensive research into the grizzly's biology and habitat requirements have been initiated. To date, most of these federal and state-sponsored efforts have been conducted in the Yellowstone and Northern Continental Divide ecosystems, but biologists have expanded their efforts to other ecosystems during the 1990s.

In 1983, the Interagency Grizzly Bear Committee (IGBC) was established under the Department of the Interior to coordinate the activities of the various federal and state agencies involved in the recovery effort. The IGBC has implemented several activities to minimize human-caused mortality and to limit contact between bears and humans. These activities include a major public education program to decrease the likelihood and danger of human-bear encounters, a coordinated law-enforcement campaign to deter poaching, and placement of bear-proof food storage containers at camp grounds to deter foraging bears. The IGBC is also using extensive mapping and computer-generated habitat models to improve land management practices. For example, selective logging of one portion of the range might be scheduled when bears are known to be foraging elsewhere. The goal is to classify public lands in one of three ways: areas essential for the bear's survival that should remain undisturbed; areas where other land uses, such as logging, can be made compatible with bear habitation; and areas where residential and recreational uses preclude bear habitation.

Since the 1982 release of the original Recovery Plan, much has been accomplished toward grizzly bear recovery. A revised Recovery Plan, approved in 1993, outlines many actions that have already been taken to manage bear populations and conserve habitat. It also establishes recovery criteria for each ecosystem, with which to determine the status of grizzly bear populations and make decisions regarding its possible delisting. The revised plan also includes a discussion of the need to manage roads in grizzly habitat; the possible importance of linkages between grizzly bear ecosystems; and a strategy to maintain genetic diversity in the isolated Yellowstone Grizzly Bear Ecosystem.

The two largest grizzly bear populations, those in the Northern Continental Divide Ecosystem and the Yellowstone Grizzly Bear Ecosystem, had, by 1994, met many of the recovery criteria established in the Recovery Plan. For smaller populations, many years of continued effort will be required to achieve recovered status. Three population criteria will be monitored in each recovery zone (within the ecosystems) to assess the status of the population and determine recovery: the number of females; the levels of human-caused mortality; and the distribution of family groups (within designated management units).

Much of the success of recovery efforts will depend upon the cooperation and support of the American public. The public perception of the grizzly as a vicious, human-assaulting predator is largely undeserved, although the dangers of an unprepared hiker coming face-to-face with a "problem" bear should not be underestimated. Public outcry often demands immediate execution of offending bears and their kin. There can, however, be no wilderness without such dangers as the grizzly bear represents. It is up to public land managers to determine the tolerance of bears for human disturbance and to provide adequate warnings and protection for recreational visitors. Ongoing research should provide knowledge that will allow bears and humans to coexist.


Regional Office of Endangered Species
U.S. Fish and Wildlife Service
Eastside Federal Complex
911 N.E. 11th Ave.
Portland, Oregon 97232

Regional Office of Endangered Species
U.S. Fish and Wildlife Service
P.O. Box 25486
Denver Federal Center
Denver, Colorado 80225


Craighead, F. J., Jr. 1979. Track of the Grizzly. Sierra Club Books, San Francisco.

Erickson, A. W., et al. 1968. "The Breeding Biology of the Male Brown Bear (Ursus arctos )." Zoologica 53:85-106.

Guilday, J. E. 1968. "Grizzly Bears from Eastern North America." American Midland Naturalist 79(1):247-250.

Herrero, S. 1970. "Human Injury Inflicted by Grizzly Bears." Science 170:593-598.

Interagency Grizzly Bear Committee. 1983. "Report of the Ad Hoc Task Force to Review the Population Status of the Yellowstone Grizzly Bear." Department of the Interior, Washington, D.C.

Moore, W. R. 1984. "The Last of the Bitterroot Grizzlies." Montana Magazine 68:8-12.

Russell, R. H., et al. 1978. "A Study of the Grizzly Bear (Ursus arctos ) in Jasper National Park." Report. Canadian Wildlife Service, Edmonton.

U.S. Fish and Wildlife Service. 1982. "The Grizzly Bear Recovery Plan." U.S. Fish and Wildlife Service, Portland.

U.S. Fish and Wildlife Service. 1993. "The Grizzly Bear Recovery Plan (revision)." U.S. Fish and Wildlife Service, Portland.

Zager, P. E. 1983. "Grizzly Bears in Idaho's Selkirk Mountains: An Update." Northwest Science 57:299-309.

Grizzly Bear

views updated May 08 2018

Grizzly bear

The grizzly bear (Ursus arctos ), a member of the family Ursidae, is the most widely distributed of all bear species . Although reduced from prehistoric times, its range today extends from Scandinavia to eastern Siberia, Syria to the Himalayan Mountains, and, in North America, from Alaska and northwest Canada into the northwestern portion of the lower 48 states. Even though the Russian, Alaskan, and Canadian populations remain fairly large, the grizzly bear population in the northwestern continental United States represents only about 1% of its former size of less than 200 years ago. Grizzly bears occupy a variety of habitats, but in North America they seem to prefer open areas including tundra , meadows, and coastlines. Before the arrival of Europeans on the continent, grizzlies were common on the Great Plains. Now they are found primarily in wilderness forests with open areas of moist meadows or grasslands .

Female grizzly bears vary in size from 200450 lb (91204 kg), whereas the much larger males can weigh up to 800 lb (363 kg). The largest individualsfrom the coast of southern Alaskaweigh up to 1,720 lb (780 kg). Grizzly bears measure from 6.59 ft (22.75 m) tall when standing erect. To maintain these tremendous body sizes, grizzly bears must eat large amounts of food daily. They are omnivorous and are highly selective feeders. During the six or seven months spent outside their den, grizzly bears will consume up to 35 lb (16 kg) of food, chiefly vegetation, per day. They are particularly fond of tender, succulent vegetation, tubers, and berries, but also supplement their diet with insect grubs, small rodents, carrion, salmon , trout, young deer, and livestock, when the opportunity presents itself. In Alaska, along the McNeil River in particular, when the salmon are migrating upstream to spawn in July and August, it is not unusual to see congregations of dozens of grizzly bears, along the riverbank or in the river, catching and eating these large fish.

Grizzly bears breed during May or June, but implantation of the fertilized egg is delayed until late fall when the female retreats to her den in a self-made or natural cave, or a hollow tree. Two or three young are born in January,
February, or March, and are small (less than 1 lb/0.45 kg) and helpless. They remain in the den for three or four months before emerging, and stay with their mother for one and a half to four years. The age at which a female first reproduces, litter size, and years between litters are determined by nutrition, which induces females to establish foraging territories which exclude other females. These territories range from 1075 mi2 (26194 km2). Males tend to have larger ranges extending up to 400 mi2 (1,036 km2) and incorporate the territories of several females. Young females, however, often stay within the range of their mother for some time after leaving her care, and one case was reported of three generations of female grizzly bears living within the same range.

Grizzly bear populations have been decimated over much of their original range. Habitat destruction and hunting are the primary factors involved in their decline. The North American population, particularly in the lower 48 states, has been extremely hard hit. Grizzly bears numbered near 100,000 in the lower 48 states as little as 180 years ago, but, today, fewer than 1,000 remain on less than 2% of their original range. This population has been further fragmented into seven small, isolated populations in Washington, Idaho, Montana, Wyoming, and Colorado. This decline and fragmentation makes their potential for survival tenuous. The U. S. Fish and Wildlife Service considers the grizzly bear to be threatened in the lower 48 states.

Little has been done to protect this declining species in the lower 48 states. In 1999 it was agreed to begin slowly reintroducing grizzlies into the 1.2 million acre (49,000 ha) area of the Selway-Bitterroot Wilderness on the border of Idaho and Montana. Unfortunately, the project was put on hold as of 2001 due to unfounded fear of the animal. Habitat loss due to timbering, road building, and development in this region is still a major problem and will continue to impact these threatened populations of bears.

[Eugene C. Beckham ]



Nowak, R. M., ed. Walker's Mammals of the World 5th ed. Baltimore: Johns Hopkins University Press, 1991.


"Interior Department Caves in to Grizzly Bear Scare." USA Today, August 6, 2001.


Craighead Environmental Research Institute. [cited May 2002]. <>.

"New Grizzly Bear Recovery Plan: Bad News for Bears." Wild Forever, 1993.

grizzly bear

views updated May 23 2018

grizzly bear Large bear, generally considered to be a variety of brown bear (Ursus arctos) although sometimes classified as a separate species (U. horribilis). Once widespread in w North America, the grizzly is now rare except in w Canada, Alaska, and some US national parks. Length: to 2.5m (7ft); weight: 410kg (900lb).