Brown Bear (Ursus arctos) Fact Sheet: Physical Characteristics

A massive bear with small, round eyes and ears, a dished-in snout, distinct shoulder hump, powerful body; only Polar Bears are heavier.

Diet largely determines size (Schwartz et al 2003)

• Largest brown bears have access to meat
• Bears with vegetable diet are smaller.

Pelage

• Color varies from pale tan, blond, gold, many shades of brown to near black, and gray or silver. (Pasitschniak-Arts 1993)
• Black and partial black fur phases in eastern and central Asia. (Garshelis 2009)
• Grizzly's guard hairs often pale at tips
• Underfur grown in fall and molted in spring

Males 1.2-2.2 times larger than females - extreme dimorphism.

Most likely due to competition between males during breeding season.

Largest Brown Bears - Western Alaska and British Columbia; Kodiak and Admiralty Islands.
Teeth and skulls not as specialized for biting and shearing as those of many meat-eating dogs and cats. (Sacco and Van Valkenburgh 2004)

• No shearing molars (carnassials)
• Canine teeth long
• First three premolars small or not present
• Molars broad, flat
• Teeth suited for wide variety of food items from insects to large ungulates

Most reliable way to distinguish a Black Bear skeleton from that of a Grizzly Bear: (Gordon 1977)

• Grizzly's 1st molar in lower jaw is longer than 20.4 mm (.8 in) and wider than 10.5 mm (.4 in)

Other good ways to distinguish Black and Brown Bears:

• Grizzly has shoulder hump; Black Bear doesn't
• Grizzly has "dished' (concave) snout that is shorter than a Black Bear's
• Grizzly's ears are short and rounded; Black Bears' are larger and more pointed
• Grizzly's claws are much longer.

Eyesight not keen but used for finding berries and nuts
Hearing and sense of smell acute.
Feet plantigrade (walk "flat-footed"); soles hairy

• Five digits on each limb
• Very long slightly curved claws 5-10 cm (2-4 in)

• Claws used for digging; not well adapted for climbing trees

Female has 6 teats
Digestive tract similar to other carnivores except for its length (more surface for absorbing plant nutrients)
No fat deposits on artery walls (no arteriosclerosis); can gain significant weight in autumn (and lose in spring) with no ill effects. (Craighead 1979)

• Recent studies suggest bears finely regulate calcium levels in blood and prevent its deposition in artery walls, which in turn prevents plaque build-up. (Gamble 2006)

Physiology differs from other carnivores - have a period of winter dormancy (hibernation) with profound changes in body chemistry, metabolism, breathing rate, and moderate changes in body temperature (Schwartz et al 2003)

• Females with young may loose up to 43% of body mass during denning. (Garshelis 2009)

Polar-Bear/ Grizzly hybrids are fertile (Davis 1950)

Color can vary from pale tan, blond, gold, many shades of brown to near black, and gray or silver.

Image credit: © San Diego Zoo Wildlife Alliance. All rights reserved.

Craighead (1979)
Garshelis (2009)
Kurt (1990)
Pasitschniak-Arts (1993)
Sacco and Van Valkenburgh (2004)
Schwartz et al (2003)