Ursus arctos
(Grizzly or Brown Bear)

Order: Carnivora
Order Description: Carnivores
Family: Ursidae
Family Description: Bears

Grizzly bears are called “grizzly” because of the white or frosted tips of the hair on their upper side.This gives them a “grizzled” appearance.  They have a range of colors, from some being almost black, much like a black bear, to grizzled brown, to a blonde or even almost a chocolate brown color.They are larger than black bears, their adult weight ranges from 325 to 1700 pounds (150-785 kg).The wide range of weight occurs because coastal bears in Canada and Alaska have an abundance of food from spawning salmon, while bears living in the interior in places like Glacier and Yellowstone Parks rarely weigh more than 550 to 600 pounds.A distinguishing difference is the line of the forehead to the snout is concave (rather than straight in the black bear), and adults have a fairly distinct hump across their shoulders.Their claws are much longer, up to 4 inches in adult grizzlies, which helps distinguish the track from a black bear.Total length is 6 to 7 feet (180-213 cm), tail length is about 3 inches (76 mm).

Historically, the grizzly ranged over most of western North America, except in very dry regions.It currently is found in Alaska, northern and western Canada, the Cabinet-Yaak mountains of northwestern Montana, the Northern Continental Divide Ecosystem in Montana (Glacier Park region), the Selkirk Mountains in on the Montana and Idaho northern border, the northern Cascades (Washington), and the Yellowstone Park ecosystem(Wyoming/Montana/Idaho).It is most common in Alaska parts of Canada in large wilderness areas.In the lower 48 states (those south of Canada) the grizzly bear’s range is estimated to be 1 to 2 percent of its former range, and its population may be as low as 1 percent of it historic population size.

Mostly arctic or alpine tundraClick word for definition and subalpine mountain forests. In Idaho, occupies lodgepole pine/Douglas-fir forests near Yellowstone, and cedar/hemlock, spruce-fir, lodgepole/larch, and shrub fields in Selkirk Mountains. In the southeastern part of Idaho, adjacent to Yellowstone, grizzlies are still occasionally attracted to garbage left in the open by ill informed recreationists.This usually leads to the bear either being killed or captured and transported elsewhere.

The grizzly is certainly considered a carnivore, but its diet is dominated by plant material. It also eats carrionClick word for definition, especially in the early spring after emerging from hibernationClick word for definition, mammals, fish, insects, and garbage. In the Yellowstone area a study found ungulateClick word for definition remains composed major part of early season diet, graminoidsClick word for definition (grasses) dominated in May and June, and whitebark pine seeds were important in late season prior to hibernationClick word for definition; berries composed minor portion of scatsClick word for definition in all seasons. Selkirk study reported extensive feeding on huckleberries in summer.Grizzly bears prey on elk and moose calves in the spring when the calves are first born.By the end of 4 weeks after birth, elk calves can usually outrun grizzlies.Grizzlies rarely prey on adult ungulates, unless the animal is wounded or unhealthy.Most adults can outrun a bear.

Grizzlies tend to be crepuscularClick word for definition, their least activity occurs at midday, but much individual variation exists. Like black bears, they often rest in day beds in forest cover.They hibernateClick word for definition and enter dens in  October and November, emerging in April and May (in Idaho, hibernationClick word for definition occurs October through April).They typically dig their own den, usually on steep northern slope where snow accumulates. They rarely use the same den more than once.Individuals may congregate in areas with abundant food, but are otherwise solitary, except when breeding or caring for young.Males do not help care for young.A Yellowstone region study found that berry crop scarcity and large pine seed crop fluctuations were major factors limiting bear density. In the fall, prior to hibernationClick word for definition, whitebark pine nuts are a preferred source of food.Their home range exhibits much variation among areas, seasons, and individuals.A Selkirk mountain study reported adult home ranges of 226 to 454 km2, with male range generally larger than a female's. Density of the Selkirk population was about 1 bear per 40 km2. Mortality in Selkirk population is primarily due to illegal shooting.In the Yellowstone region, a major source of mortality occurs during the elk season.Grizzlies are attracted to elk carcasses left by hunter, often while the hunters are transporting part of their elk to their camps.Upon return the hunter may find a grizzly feeding on the elk that the hunter shot, and an aggressive grizzly usually ends up being shot.Educational programs are now trying to convince hunter to use pepper spray rather than guns to chase off the grizzly.Grizzlies are fast runners.They can run down elk calves, and they have been clocked at speeds over 30 mph.Obviously, a human cannot outrun them, and one shouldn’t try.We all know that in contrast to black bears, grizzlies can’t climb trees.Not true!There have been a number of observations of young grizzlies climbing trees, and on one instance in Alaska, actually climbing a tree to attack a human who had retreated up a tree.They are not as adept at climbing as black bears, and it seems that only smaller grizzlies climb.While their populations in the lower 48 states are low, they have recently stabilized.The enactment of the Endangered Species ActClick word for definition probably prevented the extinction of grizzlies in the lower 48 states.

Grizzlies breed late spring-early summer, the females at 2 to 4 yr intervals. During courtship and mating, the males may be with a female for up to two weeks. ImplantationClick word for definition of the fertilized egg is delayed; GestationClick word for definition lasts about 184 days.Young are born in hibernationClick word for definition in January. LitterClick word for definition size varies from 1 to 4 (average 2). Young remain with their mother first two winters, but are usually forced to leave in the spring when the female is courted by a male. Females breed first at 5 to 6 years of age, in their southern range, 6 to 9 years in the north.With such a low reproductive potentialClick word for definition and loss of habitat, it is no wonder that their populations are endangered.

Status: Protected nongame species
Global Rank: G4
State Rank: S1

Important State References:
McCracken, J.G., D. Goble and J. O'Laughlin. 1994. Grizzly bear recovery in Idaho. Idaho Forest, Wildlife and Range Policy Analysis Group. Univ. of Idaho. Moscow. 110pp.

Information written by Donald Streubel,© 2000
Photos by Don Streubel and from © Corel Corporation, 1993 - Corel Professional Photo Series # 94000, Yellowstone National Park, #94080.
Map image provided by
Stephen Burton, 2000
Design by Ean Harker 1999, 2000.