In an 1887 census, the once countless plains bison (Bison bison bison) were reduced to 541 individuals by overhunting. Since then, conservation efforts have reestablished this subspecies in Oklahoma and Montana.

The other subspecies, the wood bison (B. bison athabascae), is listed as endangered.

These bovids graze in large herds, preferably on mixed-grass and short-grass prairie.

American bison are the largest land mammals native to the western hemisphere, although the females are much smaller than the males.

Both sexes have horns.

During the breeding season, the males fight over access to the females.

Bison share several bacterial infectious diseases with cattle that some ranchers fear may be transmittable to livestock, although studies suggest this is unlikely.

Animal Facts

Name: American Bison (Bison bison)

Family: Bovidae (Cattle and Relatives)

Range: Western Canada, northwestern United States

Habitat: Prairies, open woodlands

Diet: Grasses, grasslike plants, berries, lichens, and horsetails

Head and Body Length: 6.5 to 13 feet (2 to 4 m)

Tail Length: 20 to 24 inches (50 to 60 cm)

Shoulder Height: 5 to 6.5 feet (1.5 to 2 m)

Weight: 700 to 2,200 pounds (320 to 1,000 kg)

Life Cycle: Mating June to September; gestation 270 to 280 days, one calf born

Description: Shaggy, brownish-black hair on head, neck, shoulders and forelegs; light brown hair on hindquarters; large, heavy head; short, upturned horns; bearded chin; shoulder hump on males

Conservation Status: Lower Risk (Conservation Dependent)

Major Threat: Habitat loss

What Can I Do?: Visit the National Wildlife Federation and Buffalo Field Campaign for information on how you can help.