Learn More About:
American Bison

American Bison (Plains and Wood species) are not true buffalo.
Kingdom: Animalia
Family: Bovidae
bison (Plains)
Related species:
Canadian Wood Bison
European Bison (wisent)
Asian Buffalo
Indian Buffalo
Domestic cattle

Origins and Evolution

The ancestors of today's American Bison probably crossed the Bering Land Bridge connecting Asia and Alaska during the Pleistocene Epoch, about 500,000 years ago. Sea levels were lower at that time, with much of the water trapped in ice. Eventually, they roamed over most of what is now the United States, even to near the Atlantic Coast, and parts of Canada and Mexico. Being grazers, they thrived in and near plains environments.

Two different bison ancestors have been preserved in La Brea Tar Pits in the Los Angeles area in California. They are the Ancient Bison (Bison antiquus) and Long-horned Bison (Bison latifrons). The Ancient Bison looked much like today's American Bison, except that it was taller. It is the most common large herbivore found in the tar pits. The Long-horned Bison had a horn spread of about six feet and the horns spread outwards, rather than curling inwards (see web pages of the George C. Page Museum).

Evidence from the tarpits indicate that the bison were migratory - clusters of age groups of bison, each 1 year apart, are found in the tar, indicating that the bison were typically there for only a few months of each year.
Physical Characteristics:

Adult American Bison stand 5 - 6 feet tall at the shoulder and are 6 - 9 feet long, not including the tufted tail, which can be 3 feet. They weigh 700-2000 pounds after maturity, which is reached within three years. This makes them the largest land mammal in North America. They may live up to 30 years, although 15 - 20 is more normal.

The head and forequarters are covered with long woolly hair, whereas the smaller hindquarters have shorter hair. The hair falls off in clumps in the spring, leading to a patchy appearance. The bison's color is lighter in the summer and darker in the winter. Both genders have sharp, black, curved horns which can be 18 inches long. The horns are hollow. Their hooves are circular but cloven, leaving a distinctive round print.

The hump is structural, supported by underlying extensions of the vertebrae, rather than made of fat like a camel's. Bulls can run as fast as 30 miles per hour.

Geographic Range: Historic, recent past, and current.

Historically, American bison ranged the western plains in numbers estimated between 30 and 70 million. They were a principle resource of the Plains Indians, furnishing skins, food, bones, and fuel in the form of dried dung. In the early 1800s, Lewis and Clark's expedition encountered a herd in South Dakota, and wrote that the bison darkened the plains in their multitude. However, by that time, the smaller herds that had existed east of the Mississippi were already gone. In the 1830s, as many as 250 bison per day were hunted for hides and meat, and also as a means of controlling Plains Indian populations.
American Indian petroglyph of a bison
The coming of the railroads further decimated the herds, as people had access and rapid transportation to areas not previously economical to hunt. Some people hunted bison from the trains themselves. Some were killed simply for their tongues. By 1883, only a few hundred bison remained.

The first conservation measure occurred in 1894 when Congress made bison hunting in Yellowstone National Park illegal. In 1902, the Yellowstone herd was augmented with bison purchased from private breeders. By this time, the Yellowstone herd was the only herd left in the lower forty-eight (a herd of related wood bison existed in Canada). Today there are as many as 4000 bison in the greater Yellowstone area alone, and 400,000 in the U.S.

All of the current population of bison in the U.S. are descended from the private herds used to supplement the Yellowstone herds. These private herds were used for meat and were experimentally cross-bred with cattle. Today, many bison in the U.S. have cattle genes (are hybrids) rather than being "pure" bison. The Yellowstone herd remains genetically pure

Calves are born from April through August, mostly in May. Gestation is approximately nine months.They start out with a red coat which changes to brown by about five weeks of age. They are able to walk and run within hours of birth. Only one calf is born to a cow at a time. Calves may continue nursing for up to a year, although they begin grazing when quite young. Cows become sexually mature by age two or three and bulls by age three.
Breeding season is July through August and early September. Up until then, bulls live in "bachelor herds" and cows and calves live in seperate herds. Within these herds, there is a pattern of dominance which generally determines breeding frequency. In the rutting, or breeding, season, the bulls join the cow herds and choose specific females to follow.

Bison shed their winter coats in spring, giving them the characteristic shaggy appearance. Eventually they rub off or shed all the long hair except on their heads, front legs, and rumps.

Bison are grazing animals and migrate with the seasons. They eat grasses, forbs, and some shrubs. A bison will eat up to three percent of its body weight per day.

Although bison appear slow and clumsy, they can run up to thirty miles per hour over open ground.