Some Basic Bison Information

A Historical Perspective

Great herds of bison once roamed North America between the Appalachian Mountains on the east and the Rockies on the west. It is estimated that around 30 million bison roamed the continent when Columbus landed. The herds were so large that the bison became a symbol of the seemingly endless resources of the continent.

People have hunted North American bison for more than 12,000 years. Early European explorers and settlers killed the bison for the same reasons that Native American tribes hunted them - for their meat and hides. Unlike the Native Americans who utilized virtually all of the bison, however, white hunters became extravagant and wasteful. Taking only delicacies like the tongue, they left tons of meat and hide to rot. Railroad crews decimated what was left of the bison, as railroads cut across the herds' home range.

By 1888, only 541 bison remained in the U.S. Efforts began to prevent the species from becoming extinct. William Temple Hornday (1854-1937), an American zoologist, had a significant influence on the efforts to protect and increase the herds.

A 1905 a census indicated there were 835 wild bison and 256 bison in captivity at that time. Sanctuaries, zoos, and parks were safe havens for bison and helped to increase their numbers. The first national preserve for bison was founded in 1907 near Cache, OK and later became the Wichita Mountains National Wildlife Reserve. Subsequent game laws and other protective measures allowed the surviving bison to live and multiply. Today about 350,000 bison live in the U.S., and bison can be found in all 50 states. Large herds can be found in many natural areas, parks, and refuges, but the majority of the bison are found on private ranches.

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"Buffalo" or "Bison" ?

"Oh, give me a home, where the buffalo roam ...." Although most of us in North America refer to bison as "buffalo," true buffalo are confined to Africa (cape buffalo) and Southeast Asia (water buffalo). True buffalo - the water buffalo for example - have 13 pairs of ribs whereas bison have 14. The American bison is the largest of native North American land mammals, outweighing its closest rivals, the moose and the big brown Kodiak bear.

The word buffalo derives from the Latin word bufalus.
Bison comes from the old Germanic word for ox: wisent.


Bison priscus

steppe wisent of Europe and Siberia hunted by Cro-Magnon man - a huge beast

Bison latifrons

50% larger than our modern bison with horns spanning 7-9 feet

Bison antiquus

hunted by Folsom man approximately 10,000 years ago.

Bison occidentalis

a large plains bison

Bos bison

our modern bison

Based on genetic analysis, bison have been reclassified from the genus Bison into the genus Bos. Bos encompasses the "ungulates" (cloven hooves), and now includes all wild cattle and the domestic Bos taurus as well as the three subspecies of bison:

Bos bison bison

plains bison

Bos bison athabascae

wood bison

Bos bison bonasus

European wisent (endangered)

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Vital Statistics

Bison are social animals and live in herds that change in size and composition throughout the year. In winter, herds are much smaller, typically only 20 to 30 in number, with older bulls completely isolating themselves. During the rut (mating) season in summer, bison gather in very large herds. Herds are definitely matriarchal with cows usually leading herd movement.

Bulls weigh from 1,600 to 2,000 pounds, stand between 5.5 and 6.5 feet high at the shoulder, and measure from 9.5 to 11.5 feet in total length (including the tail). Bulls seldom live longer than 20 years but, in rare cases, may live to be 40 years old.

The cow is smaller, weighing up to 1,100 pounds, although most weigh about 1000 pounds. They stand 4.5 to 5.5 feet in height at the shoulder, and are less than 10 feet in length. Less shaggy on the head and chin, she has a smaller hump and her horns are more slender and curved than the bull's.

A bison's coat attains prime condition during the winter months, then sloughs off in clumps during the annual molt in the spring. The biggest chunks come from the hump and shoulders, where fur is two to five times thicker than the hair on the hindquarters. This difference in thickness accentuates the hunchback shape. The hair on forelegs, throat, chin, crown, and forehead reaches surprising lengths, especially on older animals. The longest masses, dangling from between the horns and upper forehead, have been known to grow to 22 inches.

Bison are subject to the same diseases as cattle but in the wild seem to be amazingly free of disease. No serious epidemics have been reported in present-day animals. Some animal breeders have tried to develop a hardy, useful kind of domestic animal by crossing American bison with ordinary domestic cattle. The cattaloes or beefaloes that result have not proven satisfactory, primarily due to infertility problems.

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Herd Origin & Management

The Tallgrass Prairie bison herd was started with 300 animals donated by the Ken-Ada Ranch north of Bartlesville in the fall of 1993, and christened the Christina Adams Bison Herd (for the daughter of the Ken-Ada Ranch owners, Kenneth and Dianna Adams). The herd has since grown, more or less according to schedule. The target size is a summer herd of 2,600, including calves, with an over-wintering herd of 1,950, in a 23,000 acre fiire-bison unit.

All heifer calves are vaccinated against brucellosis and all incoming animals are tested for brucellosis and tuberculosis and quarantined before admission to the herd. Even though there is no substantiated evidence of bison to cattle transmission of brucellosis, great pains are taken to ensure the herd remains brucellosis free. During the annual roundup all keeper animals are vaccinated for several bovine diseases and treated for external and internal parasites.

Genetic mixing is controlled by the importation and culling of breeding bulls. Bulls have been obtained from a number of sources, including: Custer State Park, SD; Cross Ranch Preserve, ND (TNC); Fort Niobrara NWR, NE; Fort Robinson State Park, NE; KS Parks & Wildlife, Garden City Herd, KS; Ken-Ada Ranch, OK; Maxwell Game Refuge, KS; National Bison Range, MT; Niobrara Valley Preserve, NE (TNC), Samuel H. Ordway Memorial Prairie, SD (TNC); Sedgwick County Zoo, KS; and Wichita Mountains NWR, OK.

Bulls are sold at 6-7 years of age, since after this they tend to become more aggressive and dangerous. Cows are sold at 10-12 years of age. They are still productive through their early twenties but their sale value is higher as teenagers. Also, the older cows are less physically fit for withstanding the rigors of roundup.

The herd receives no supplemental feeding, but, because the animals are in a restricted range, salt with trace minerals is provided. Water is available in creeks and ponds.

For research and record-keeping purposes, each individual bison in the herd is identified with an ear-tag transponder. This tag is read by holding a wand near the animal's head; the wand transmits the tag's data to a portable computer. Each transponder transmits a unique number, which is then assigned to that particular animal. Some of the information tracked includes the animal's sex, origin, age, weight, pregnancy status, and general health. Due to the lack of a 'standard tag', the tags have been changed several times. Recently the International Standards Organization (ISO) published a standard for herd animal tags. During the 2002 roundup the tags were replaced with ISO-standard e-tags, which should simplify this aspect of the herd management.

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Bison Breeding

The rutting season, which varies slightly from north to south, begins about mid-June and wanes towards the end of September. Heifers typically first breed at 2 years of age and calve at 3. Calves, weighing 30-40 pounds at birth, are usually born in April or May after a gestation period of 9.5 months. Cows are able to produce calves until they are about 15 to 20 years old, typically one calf per year. Twins are very rare.

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Bison Grazing

Like domestic cattle, bison are grazers. However, they prefer young, tender grasses and eat few forbs (such as wildflowers). They walk along biting off mouthfuls of grass, barely chewing it before swallowing. Cud-chewing occurs later in the day when the hastily swallowed grass is brought up, portion by portion, to be broken down more completely in a second chewing. Feeding mainly in early morning and the late afternoon, bison normally rest and chew their cud during mid-day and at night. Research at the preserve has found that not less than 99% of a bison's diet is grasses and sedges. The bison's rubbing on young trees helped prevent trees from invading the prairie. When necessary, bison will travel a long way to find water; however they can go for long periods without it.

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Bison Wallowing

Wallowing is practiced by both sexes and all age classes. Wallows are usually in dry areas, but wet areas may be used. This behavior seems to be important in grooming, sensory stimulation, alleviating skin irritation, and reproductive behavior. Dust, which packs into the hair after wallowing, probably minimizes the effects of insects.

Wallows also serve as water reservoirs, making small ponds that become available to vertebrates and invertebrates for multiple uses; in addition, such ponds enhance growth of specific vegetation needing moist or wet habitat. Wallowing behavior also transports soils and seeds to other areas because the thick fur on the head and forequarters is ideal for dispersal of awned, barbed, and sticky materials.

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Bison Predators

Historically, the bison's most important predators were wolves. Wolves constantly followed the large herds, culling the old, incapacitated, and very young animals. Even solitary adult bulls were not immune to attack. To a lesser extent native human Americans were predators of the bison. Grizzlies occasionally killed bison, and mountain lions and coyotes were also occasional opportunistic predators of young calves.

But one of the primary killers, before the slaughter by humans in the late 1800s, were iced-over rivers. Thousands of bison drowned, particularly in the northern U.S., when the enormous weight of crossing herds caused the ice to give way.

Since the wolf and grizzly bear are gone from the tallgrass prairie region, man is the remaining predator. The Nature Conservancy has no plans to reintroduce wolves to the Tallgrass Prairie. It isn't big enough and they and our neighbors' cattle wouldn't mix well; so that means no wolves - ever!

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Bison Personality

Bison aren't serious all the time. Young bison are thought to play. Play is manifested by seemingly purposeless frolicking, including chasing, battling, butting, kicking, and racing. Such activity aids muscle development and coordination important later in life.

Although bison have keen sense of smell, their eyesight is poor. They maintain contact with one another by uttering hog-like grunts. Bison are ordinarily mild-mannered, even dull, animals but can be aggressive. Threat postures, which may be a prelude to fighting, include a snort or a growling, guttural bellow with head up, mouth wide open, and tail erect. Heed these warnings!

For your safety, when visiting a bison herd, please observe the following rules:

  • Rule #1: Stay in your car!

  • Rule #2: Stay in your car! Bison are fast - they can go from 0 to Oops! (up to 35mph) faster than you can say it! If they're blocking the road, wait. Though they may be big and fuzzy, bison are essentially wild animals and are not cuddly.

  • Rule #3: Stay in your car!

For more on bison behavior read Where Buffalo Roam published by the Badlands Natural History Association, and available in the preserve's visitor center.

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Bison Meat

Bison meat is a tasty, high-quality source of protein, with significantly less calories, fat, and cholesterol per serving than beef, pork, or chicken. For more information on the nutritional value of bison meat, check professional sources such as the National Bison Association.

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Bison/Cattle Comparison

Grazing Behavior

Bison have a much stronger herding instinct and are much more mobile. They tend to move constantly, even when grazing, producing a more intensive, short-duration grazing effect.


Bison consume a larger proportion of grasses and less forbs and shrubs.


Bison more effectively digest low-quality forage. Cattle have greater digestive efficiency on high-quality (e.g., feedlot rations) diets.

Range Utilization

Bison grazing is less restricted by water availability, slope, elevation, and shade. Bison are more attracted to preferred forage, such as the lush new grass that follows a fire.

Winter Foraging

In many areas, grass-fed cattle must be given protein supplement during the winter. Bison maintain themselves and have much lower weight losses on poor quality winter forage (cured, low nutrient standing grass). Bison forage down through snow-cover and will eat snow to meet their water requirements.

Cold Stress

Bison have higher overall cold resistance: better insulation, lower winter metabolic rates, and lower external critical temperature.


Bison create and maintain wallowing areas (small scale patch disturbances) and actively rub themselves on trees and other suitable objects.


Bison are hardy animals with natural resistance to bovine diseases and possess an exceptional ability to recuperate from injuries. They require less handling (worked only once per year) and no growth hormones. With sufficientspace, grass, water, herd age/sex structuring, and sound fence construction (6-foot barbed-wire fence) containment is not a problem. Losses to predation are simulated by culling calves and older cows and bulls.

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Summary of Bison Facts

  • Bison is the correct term for the mammals on the Tallgrass Prairie Preserve. According to scientists, true buffalo are confined to Africa and Southeast Asia.

  • Before the settlements of modern civilization, around 30 million bison roamed across North America. By 1890, fewer than 600 plains bison were alive.

  • Bison and cattle are cousins (that is, they are in the same genus, Bos).

  • Bison are the largest native animals on the North American continent.

  • Full-grown bison bulls stand about 6.5 feet at the shoulder and can weigh up to 2,000 pounds.

  • Adult bison consume more than 30 pounds of grass (air-dry weight) in a day.

  • Bison can jump 6 feet vertically. Because they reportedly can jump more than 7 feet horizontally, "bisonguards" on the Preserve are 14 feet wide. (This is double the standard width of a cattleguard.)

  • Bison can run speeds up to 35 miles per hour.

  • Bison are powerful swimmers, navigating with all but hump, muzzle, and top of the head submerged.

  • Both sexes have horns; the cow's are smaller. A bull bison can be identified from a cow by wider, thicker horns; a wider skull; and a generally more massive structure.

  • The gestation period for bison is 9.5 months.

  • Bison calves are generally born in the spring and weigh 30-40 pounds.

  • The bison was named the state mammal of Oklahoma by the legislature in 1972.