Bison / Buffalo

"...its toughness and hardy endurance fitted it to contend with purely natural forces...to resist cold and wintery blasts or the heat of the thirsty summer, to wander away to new pastures, to plunge over the broken ground, and to plow its way through snow drifts or quagmires." Theodore Roosevelt

History

The American bison or buffalo (Bison bison), is the largest mammal on the North American continent. This magnificent creature, which is a member of the cow family Bovidae, was given its common name by early French explorers who called them "les boeufs," meaning oxen. Throughout the years, the name went through several changes from "buffle" to "buffelo" and finally to its present "buffalo." Bison is the correct scientific and common name, but buffalo is widely used and accepted. Bison were given many names by native peoples, including "tatanka," "pezhekee," and "iinii," among many others.

Paleontologists have traced the ancestors of the American bison to southern Asia during the Late Pliocene, approximately 3 million years ago. Ancient bison were much larger than the present-day animal and ranged throughout the northern hemisphere. One prehistoric bison species, Bison latifrons, had horns measuring up to seven feet from tip to tip. The fossil record shows that over time bison went through many evolutionary changes. Bison occidentalis came about in the late Pleistocene and is a direct ancestor of modern bison.

Approximately 150,000 years ago, bison migrated to America by crossing the Bering land bridge that once connected Asia with North America. During the ensuing centuries, bison moved south and east, at one time ranging from Mexico to southern New England. The greatest concentration was found on the Great Plains where an estimated 30 to 60 million bison once roamed.

For centuries, bison and humans coexisted on the Great Plains. The bison was the mainstay of Plains Indian life, providing food, clothing, shelter, and tools. Every part of the animal could be used. This way of life persisted for thousands of years until over-exploitation by European colonials in the 1800s drove bison to the brink of extinction.

Between 1800 and 1890, market hunters and the U.S. Army organized large-scale bison hunts, killing millions of bison for their hides and decimating the species serving as the cornerstone for Plains Indians way of life. As many as 250 bison could be shot in one day by a skilled hunter, and a good skinner could remove the hide in five minutes. The peak of the bison trade was between 1870 and 1880, coinciding with railway development across the western United States. As railways expanded, personnel and supplies were transported more efficiently to and from the plains region. During this era, auctions reported moving as many as 200,000 hides every 1-2 days. The cumulative effect of this unregulated slaughter was the near extinction of the American bison. By the turn of the twentieth century, the thundering herds of millions were reduced to approximately 300 bison.

If not for the foresight of a few individuals, including Theodore Roosevelt, the American bison may have gone extinct. During the species’ decimation in the late 1800’s several private citizens began to capture and shelter bison. In 1886 the U.S. Cavalry was positioned in Yellowstone to protect the park from individuals seeking to exploit natural resources, including poaching from the dwindling bison population. It wasn’t until the Lacey Act was passed in 1894 that wildlife in Yellowstone gained legal protection and provided a mechanism to persecute offenders. The combination of legal protection and the preservation of habitat during the turn of the 20th century paved the way for bison recovery. Today, more than 500,000 bison live in North America under both public and private ownership.

In 1956, 29 bison were brought from Fort Niobrara National Wildlife Refuge in Nebraska and released in the South Unit of Theodore Roosevelt National Park. Here they roamed freely on 46,000 acres of park land and by 1962 the herd had increased to 145 animals. That year, 10 bulls and 10 cows were relocated to the 24,000-acre North Unit.

Though both units of the park can carry larger numbers of bison, park managers have currently set herd size at approximately 200 to 400 animals for the South Unit and 100 to 300 for the North Unit to maintain healthy range conditions. Learn more about Bison Management.

Biology

Warning: Bison are wild animals and can be dangerous if provoked. They can run up to 35 miles per hour, jump 6 feet vertically, and pivot quickly. Always view them at a distance and give them the right-of-way if encountered on a trail or the road. It’s recommended to keep at least 25 yards between you and bison you’re observing. When bison are in the road, be patient, stay in your vehicle, and observe them quietly. On trails, make a big detour around them, move slowly, and make sure they are aware of your presence to avoid surprising them. Keep dogs under control at all times; wild animals are often nervous when dogs are nearby and bison may charge if dogs are too noisy or too close. If a bison raises its tail, especially if the tail is straight up in the air, a charge may be imminent.

Full-grown bulls weigh up to 2,000 pounds and stand six feet or more at the shoulder. Bulls have massive heads which are covered with thick, long, wiry fur. The shoulders carry a huge hump that gives the bison its characteristic top-heavy look, with the hips being much smaller than its torso. A bison cow is similar in appearance to the bull, but is smaller in size, weighing up to 1100 pounds and reaching a height of five feet tall at the shoulder. Both sexes of bison have horns. Bulls have a life expectancy up to 15 years and cows can live up to 20 years old.

Bison group sizes fluctuate throughout the year, typically being largest during the summertime and smallest during the winter. Cow groups are typically composed of cows, calves, yearlings, bulls under 3 years old, and are led by an older cow. Bulls become progressively more solitary as they age but will still periodically join bachelor groups of other bulls or occasionally cow groups. Groups move on average 2 miles a day while grazing.

The mating season, also known as “the rut”, typically peaks in July. Bulls will rejoin the herd during this time and pursue cows. Prime breeding age for bulls is 6-10 years. Sometimes bulls challenge each other, crashing heads and trying to hook each other with their horns until one or the other backs down. However, in most cases, loud bellows, standing broadside to show size, and mock charges suffice and battles are avoided. Bulls do not have territories or collect harems of cows. Instead, bulls pick out one cow at a time and stay by her side, sometimes for several days, fending off other bulls until mating is completed. This behavior is called tending. By the time the rut is over, a prime bull may lose up to 200 pounds.

Cows usually conceive for the first time at two or three years olds. Though calves can be born at any time of the year, the calving season usually begins in April after a 9 month gestation period. Calves are orange-red in color and are up and moving within 3 hours of birth. They stay very close to their mother for the first few weeks. Cows are very protective of their young. Eventually, calves venture further away from their mothers, playing with other youngsters in nursery groups, while always under the watchful eyes of other cows within the herd. After 3 months, the orange-red coloration changes to dark brown and the hump and horns begin to form.

Bison are herbivores (plant eaters) and feed primarily on grasses and forbs. They are often seen in or near prairie dog towns where they find a continual supply of new grass shoots and can wallow in the loose soil. Bison have excellent hearing and a keen sense of smell. Wolves and grizzly bears are the natural predators of the American bison, but both have long been extirpated from Theodore Roosevelt National Park.

.