Mammals · Carnivora · Ursidae

Brown Bear

Ursus arctos horribilis

Not Evaluated

It has not yet been assessed against the IUCN criteria. See full glossary

The grizzly is the interior subspecies of the brown bear in North America, smaller than the coastal bears of Alaska because it has less salmon available. It is omnivorous and opportunistic: roots, berries, insects, rodents, carrion and ungulates according to the season. It is recognised by the muscular hump over the shoulders and the concave facial profile. It once occupied the whole western half of the United States and today survives in Alaska, western Canada and a few ecosystems of the Rockies.

Weight

130 kg – 360 kg

Size

1.8 m – 2.5 m

Lifespan

25 years

Diet

Omnivore

Combines animal and plant food depending on availability.

Activity

Crepuscular

Active above all at dawn and dusk.

Social structure

Solitary

Lives and hunts alone, joining others only to breed.

Sighting difficulty

Unknown

Temperate forestMountainTundraGrasslandOmnivore Crepuscular Solitary Temperate forest Mountain Tundra Grassland Mammal

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Fun facts

GeneralA subspecies of brown bear; it puts on as much as 180 kg before hibernating, on salmon and berries.
The hump on its back is muscle, not fat: it is what drives the forelimbs when digging, and it is the most reliable feature for telling it apart from the black bear.
During hibernation it goes for months without eating, drinking or defecating, and even so it barely loses muscle mass or bone density; that mechanism is being studied as a route to treating human osteoporosis and muscle wasting.

Life cycle & biology

Skeleton type: Vertebrate - internal bony skeleton (mammal)
Habitat & environment: Forest, alpine meadows, tundra and river valleys of western North America
Birth weight: 400 - 500 g
Size at birth: About 30 cm; born blind and almost hairless, while the mother hibernates
Sexual maturity: 5 years
Gestation / incubation: 7 months (with delayed implantation)
Litter / clutch size: 2