“Grizzly bears are a North American form of brown bear.”
Grizzly bears are huge North American brown bears that live in forests and mountains. They eat plants, fish, and small animals, and spend winters in dens.
By An Nguyen · Published · Updated
Measured against the 176 species profiled on this site. Each figure is converted to one unit system from the published range on the page, so the ranks are computed, not quoted.
| Measure | This species | Rank here | Exceeds |
|---|---|---|---|
| Body mass | 362.9 kg | #31 of 176#22 of 90 Mammalia | 82% |
| Body length | 2.44 m | #36 of 176#23 of 90 Mammalia | 78% |
| Top speed | 56.3 km/h | #30 of 75#18 of 46 Mammalia | 58% |
| Lifespan in the wild | 25 yr | #48 of 169#24 of 85 Mammalia | 69% |
Closest in body mass
Ranks use the upper end of each published adult range, so they compare typical large adults rather than records, and metrics with no published number are left out rather than estimated. The full table is downloadable from the species dataset, and any two species can be put side by side in the comparison tool.
Browse photographs of brown bear across habitat, behavior, anatomy, and life stages.
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Core article
A closer look at habitat, diet, behavior, reproduction, and conservation.
The grizzly bear (Ursus arctos horribilis) is a large North American omnivore found from temperate forest to alpine tundra. It can take large ungulates but spends much of its foraging time eating berries, roots, and insects. Digging disturbs and aerates soil, while bears feeding on salmon carry marine nutrients inland.
Grizzlies are massive and strongly dimorphic: a mature male stands 3 to 4 feet at the shoulder, measures 5 to 8 feet long, and ranges from 400 to over 800 pounds, while females run 300 to 600. Its defining feature is the pronounced shoulder hump — not fat but a mass of deltoid muscle that powers the forelimbs for digging roots, unearthing burrowing mammals, and tearing apart logs — backed by non-retractable front claws up to 4 inches long, built for excavation rather than climbing. The thick coat ranges from blond and reddish-brown to nearly black, and pale, silvery tips on the back and shoulder hairs give the "grizzled" look and the common name, over a dense insulating undercoat for alpine and tundra cold. Despite the bulk, grizzlies are athletic, hitting 35 mph in short bursts. It is not a separate species but the North American subspecies of the brown bear (family Ursidae), whose ancestors crossed the Bering land bridge from Eurasia during the Pleistocene.
Grizzlies once ranged across much of western North America from Alaska to central Mexico and east onto the Great Plains, but eradication and human expansion have cut their range in the contiguous U.S. by nearly 98%. Robust populations now hold in Alaska and western Canada, while in the lower 48 fragmented remnants persist in protected strongholds — the Greater Yellowstone Ecosystem, Montana's Northern Continental Divide, and small pockets in Idaho and Washington. They are versatile across biomes, using temperate and boreal forest for cover and foraging, high alpine meadows in summer, and open tundra in the north, but they need vast, unfragmented wilderness to cover their large home ranges in search of dispersed seasonal food.
Despite belonging to the order Carnivora, grizzlies are opportunistic omnivores, with vegetation making up 70 to 90% of the diet. The diet is seasonal: in spring they scavenge winter-kill carrion, graze grasses and sedges, and dig roots; in summer they feed on insects, including army cutworm moths that gather in alpine talus. Late summer and autumn bring hyperphagia, a period of increased feeding before winter, when bears eat berries, pine nuts, and, along some rivers, lipid-rich salmon.
Grizzlies are predominantly solitary across large home ranges, but they aren't strictly antisocial — a rigid dominance hierarchy kicks in when bears crowd concentrated food like salmon streams and berry patches. There large mature males dominate the best spots, females with cubs rank high through defensive aggression, and subadults scavenge the margins, order maintained by scent-marking, jaw-popping, huffing, and bluff charges. Infanticide by adult males is documented: killing cubs ends lactation and can return a female to estrus sooner, so mothers with young cubs avoid areas frequented by big males.
Grizzly reproduction is slow, with high investment and delayed implantation: mating happens in spring and early summer, but the embryo stays dormant until late autumn, and if the female hasn't built enough fat through hyperphagia her body reabsorbs it. If it implants, gestation is only 6 to 8 weeks, and in the winter den she bears 1 to 3 tiny, blind, nearly hairless cubs weighing less than a pound, which grow fast on her rich milk. Cubs stay with her an extended 2.5 to 3.5 years learning to forage and navigate the social hierarchy, so females breed only every 3 to 4 years. Wild grizzlies typically live 20 to 25 years, sometimes 30.
Globally the brown bear is Least Concern, but grizzlies in the contiguous U.S. are listed as Threatened under the U.S. Endangered Species Act. Roads, housing, and agriculture fragment habitat and increase conflict when bears reach unsecured garbage, livestock, or crops. Climate-driven changes to whitebark pine and other seasonal foods may add pressure. Conservation focuses on connected habitat, attractant management, and reducing conflict near settlements.
Grizzly bears are a North American form of brown bear.
A grizzly's shoulder hump is muscle, not fat.
Grizzlies can smell food from miles away.
Cubs are born tiny during the mother's winter den sleep.
Grizzlies eat huge amounts of food before hibernation.
Despite their size, grizzlies can run faster than many horses in short bursts.
Select a question to reveal the answer.
Grizzly bears live in forests, mountains, and open valleys in Alaska, western Canada, and parts of the northwestern United States.
Grizzlies are omnivores. They eat berries, roots, grasses, insects, fish, and sometimes small mammals.
Yes. In cold regions, grizzlies spend winter in dens and live off stored fat until spring.
Grizzlies usually avoid people, but mothers with cubs or surprised bears may defend themselves. Wild grizzlies should never be approached.
Grizzly bears and polar bears are closely related species in the bear genus Ursus.
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