male bison with six small birds on its back
Birds will perch on the backs of bison, looking for insects disturbed by their grazing.

NPS Photo / Kim Acker


Perhaps no other animal symbolizes the West as dramatically as the American bison. In prehistoric times millions of these animals roamed the North American Continent from the Great Slave Lake in northern Canada, south into Mexico and from coast to coast. No one knows how many bison there were, but the naturalist, Ernest Thompson Seton, estimated their numbers at sixty million when Columbus landed. They were part of the largest community of wild animals that the world has ever known. The National Park Service has played an important part in returning the bison to the Great Plains. Click here to view the YouTube video Restoring the Thunder: Bison conservation in the Great Plains National Parks about the restoration of the American bison to the Great Plains.

Explore the Time Line of the American Bison created by the U.S. Fish and Wildlife Service.

A bison bull with frost on its fur
A bison bull stands in the frost.

NPS Photo


Bison are part of the family Bovidae, to which Asian buffalo, African buffalo and domestic cattle and goats belong. Because American bison resembled in some ways old world buffalo (Asian and African buffalo), early explorers to North America began to call them buffalo. Although it is a misnomer, the name buffalo is still used interchangeably with bison. One of the physical differences between the old world buffalo and the American bison is the large shoulder hump of the bison. This hump, along with a broad, massive head, short, thick neck and small hindquarters give the animal its rugged appearance.

The color and character of the bison's fur varies with the season. A mature bull in winter has a dark brown to black coat. The length of the hair measures up to sixteen inches on the forehead, ten inches on the forelegs, and only eight inches on the hindquarters. It is little wonder that bison, unlike domestic cattle, face into storms.



The best description of a bison's temperament is unpredictable. They usually appear peaceful, unconcerned, even lazy, yet they may attack anything, often without warning or apparent reason. To a casual observer, a grazing bison appears slow and clumsy, but he can outrun, out turn, and traverse rougher terrain than all but the fleetest horse. They can move at speeds of up to thirty-five miles per hour and cover long distances at a lumbering gallop.

Their most obvious weapon is the horns that both male and female have. But their head, with its massive skull, can be used as a battering ram, effectively using the momentum produced by two thousand pounds moving at thirty miles per hour! The hind legs can also be used to kill or maim with devastating effect. At the time bison ran wild, they were rated second only to the Alaska brown bear as a potential killer, more dangerous than the grizzly bear. In the words of early naturalists, they were a dangerous, savage animal who feared no other animal and in prime condition could best any foe. A bull with lowered head, snorting and pawing the ground, with tail stiffly upraised, conveys a universal warning of danger to all nearby that is impossible to ignore!

Other activities of the bison include rubbing, rolling, and wallowing. Wallowing creates a saucer-like depression called a wallow. This wallow was once a common feature of the plains; usually these wallows are dust bowls without any vegetation.

Bison have poor eyesight but acute hearing and an excellent sense of smell. The sounds they make range from a pig-like grunt to an aggressive bellow.

Bison mother and calf graze in the grass
A mother and calf bison grazing

NPS Photo


The rutting, or mating, season lasts from June through September with peak activity in July and August. At this time, the older bulls rejoin the herd and fights often take place between bulls. The herd exhibits much restlessness during breeding season the animals are belligerent, unpredictable and most dangerous.

Calves, born nine to nine and one-half months later in April or May, generally weigh thirty to seventy pounds. They have reddish-brown fur and do not have the conspicuous hump of the adult. After a few months, the fur begins to change to chocolate brown and the hump begins to develop.


Much has been written concerning the economic value of the bison to the American Indian. The bison sustained a way of life, providing food, clothing, shelter, and fuel. Extermination of the bison spelled the doom of American Indian independence.

In 1800, it was estimated there were forty million bison, by 1883, there were few wild bison in the United States - most were in Yellowstone National Park. By 1900, there were less than a thousand left in North America. The majority of the forty million animals were killed in a fifty-five year period, beginning in 1830. Many people denounced the slaughter; few did anything to stop it. Fortunately, a small, devoted group of conservationists managed to save a few hundred. The bison we see and enjoy today were raised from these few survivors.


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    Last updated: August 30, 2020

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