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Species Description

American Bison

Bos bison

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Phylum: Chordata
Subphylum: Vertebrata
Class: Mammalia
Order: Artiodactyla
Family: Bovidae


Rusty tan to almost black. This is the largest, most massive native land mammal of North America. The adult male bison can attain a maximum of 3.8 m (12.5 ft) in total length, stand 1.8 m (5.9 ft) at the shoulder, and weigh 1,000 kg (2204.6 lbs). Females on average are approximately 40% smaller. This large, cow-like hooved mammal has a distinct hump at the shoulder. Its head, neck, shoulders and forelegs are covered in long shaggy hair. The head is short and heavy, with short, black, curved horns. The tail is short and the tip is covered in a tuft of hair.

Life Cycle

Bison mate from early July to late September. A single calf (or rarely two) is born 9 - 9.5 months later in late April or May. Calves are yellowish to tawny in color and lack the characteristic hump of adults. Calves are very precocious and are able to follow the female within a few hours after birth. Within a few weeks the coat darkens and the hump begins to develop. Young are weaned at 7 - 8 months of age and remain with the female throughout their first winter. Bison continue to grow until 7 - 8 years of age, but sexual maturity is attained at 2 - 3 years in females, and 4 - 5 years in males.

Natural History

Bison are gregarious grazers. An estimated 30 - 40 million bison roamed the vast North American continent at the time of European contact in the 1500s. Bison are less selective than domestic cattle and consume a wide variety of grasses, forbs, and other broad-leafed plants. They are cud-chewers and have a four-chambered stomach. The daily activity of bison is very similar to that of domestic cattle. Peak feeding times are in the early morning and late afternoon, with a midday period of resting, cud chewing, and wallowing. A bison wallow is a shallow depression in the soil, which was used either wet or dry. Bison roll in these depressions, covering themselves with dust or mud which acts as a repellent to flies and other parasites. Very little is known about the ecology of bison herds east of the Mississippi River. Woodland bison lived in small herds compared to the vast herds of the western plains. The core of a herd was formed by cows, calves, and one- and two-year-old animals. Bulls stayed on the periphery, either singly or in small groups, except during the rut when they joined the main herd. The maximum lifespan of bison is 40 years, but the average is 20 years. Historical predators of bison were wolves, mountain lions, grizzly bears, and jaguars.


American Bison Region Map The historical range of the bison was extensive, from Alaska, Washington, Oregon, and Canada south into the northern portions of the Mexican plateau, and eastward to the Atlantic seaboard states, and all land in-between. Before Europeans arrived, small herds of woodland bison inhabited almost all of Georgia, except the southwestern and coastal parts of the state. By 1819 all bison east of the Mississippi River were gone forever.

Conservation Status

Bison have been extirpated in the wild throughout their range. They are maintained only in herds on ranches and in state, federal, and private parks and reserves. Private production of this species for food and hides has increased in recent years.

Similar Species

No other mammal in North America is similar in appearance to the bison.