Close-up of a bison herd beginning to stampede.

Stories in Oklahoma

6 Furry Facts and History about the Iconic American Bison

Where Did All the Bison Go?

Nestled between the Appalachian Mountains to the east and the Rocky Mountains on the west, lived an enormous herd of bison roaming across the Great Plains of central North America. It is estimated that 30 million bison were wandering the plains when Columbus landed on the eastern shores. These incredible animals were so iconic that they became a national symbol of pride for the seemingly endless resources of the newly found continent.

However, in the late 1800s these bison were almost entirely driven to extinction with less than 1,000 individual animals remaining. A census conducted in 1905 indicated that there were 835 wild bison and 256 bison in captivity at that time. Sanctuaries, zoos and parks were safe havens for these special animals and helped to sustain and increase their population size. The first national preserve for bison was founded in 1907 near Cache, OK and later became the Wichita Mountains National Wildlife Refuge.

Close-up of an American bison caught by a camera trap hidden in the tallgrass.
American bison A camera trap set up on the prairie at captures a curious bison. © Morgan Heim

Years later, hunting laws and other protective measures allowed the remaining bison to live, thrive and multiply. Today their numbers have rebounded to around 350,000—about 1% of their original herd size—but enough to keep them out of the dangers of extinction.

Approximately 15,000 animals can be found across the public lands of the United States. Remaining bison populations are in private herds such as those maintained by The Nature Conservancy.

The Nature Conservancy has plains bison (Bison bison bison) on twelve native grassland preserves in North Dakota, South Dakota, Nebraska, Iowa, Illinois, Indiana, Colorado, Kansas, Missouri and Oklahoma. Eleven of these herds are owned and managed by the Conservancy and one herd is owned by a university that manages the TNC-university owned preserve. All locations are home to year-round resident herds totaling approximately 6,000 bison across 130,000 acres of native rangeland.

Two bison seen from far way under turbulent, stormy skies at the Cross Ranch Preserve in North Dakota.
Cross Ranch Preserve
North Dakota
Cross Ranch is located along the only free-flowing section of the Missouri River in North Dakota.
Close-up of a male bison at the Samuel H. Ordway, Jr. Memorial Preserve in South Dakota.
Samuel H. Ordway, Jr. Memorial Preserve
South Dakota
Ordway Prairie lies at the southern end of large untilled landscape consisting of over 135,000 acres that extends into North Dakota.
View of the Niobrara River snaking through the preserve in fall.
Niobrara Valley Preserve
Nebraska
The Nature Conservancy's Niobrara Valley Preserve is one of the largest TNC preserves in the U.S., and a model for grassland management using bison, cattle and fire.
A herd of bison atop a hill at the Broken Kettle Grasslands Preserve in Iowa.
Broken Kettle Grasslands Preserve
Iowa
Broken Kettle is a sweeping reminder of nature’s beauty. Not only is it the Conservancy’s largest preserve in Iowa, but it contains the largest remaining prairie in Iowa.
Small group of bison eating the fall season grasses at the Nachusa Grasslands Preserve in Illinois.
Nachusa Grasslands Preserve
Illinois
In 1986, recognizing Nachusa offered the best opportunity in the state to restore a large and diverse grassland, the Conservancy purchased the core of the preserve.
A bison calf in a group of adults at the Kankakee Sands Preserve in Indiana.
Kankakee Sands Preserve
Indiana
Bison Rangers are on duty at the Bison Viewing Area on the last Saturday of every month from 10am to 4pm to answer questions about Kankakee Sands, bison and all things prairie.
Expansive view of the San Juan Mountains and grazing bison at the Zapata Ranch in Colorado.
Zapata Ranch
Colorado
In 1999, The Nature Conservancy made conservation history by acquiring this preserve, its largest in Colorado.
Close-up of adult bison eating green grasses at the Smoky Valley Ranch in Kansas.
Smoky Valley Ranch
Kansas
On this land, you'll find a sight that almost vanished from America—bison roaming a prairie as they did hundreds of years ago.
Landscape view of the rolling hills at the Konza Prairie in Kansas.
Konza Prairie
Kansas
Konza Prairie hosts decades of research on the tallgrass prairie ecosystem while welcoming visitors to experience the beauty of the Flint Hills.
Sun setting over the lush prairie at the Tallgrass Prairie National Preserve in Kansas.
Tallgrass Prairie National Preserve
Kansas
The country's only national park dedicated to the tallgrass prairie, privately owned by The Nature Conservancy.
Visitors taking a photo in a wooden frame at the Dunn Ranch Prairie Visitor's Center in Missouri.
Dunn Ranch Prairie
Missouri
Dunn Ranch Prairie boasts breathtaking views of expansive grasslands, a thriving bison herd, hundreds of vibrant wildflower species and over 100 species of birds.
Bison calf resting the the lush grasses at the Joseph H. Williams Tallgrass Prairie Preserve in Oklahoma.
Joseph H. Williams Tallgrass Prairie Preserve
Oklahoma
The Joseph H. Williams Tallgrass Prairie Preserve is the largest protected remnant of tallgrass prairie left on earth.

The Nature Conservancy Bison Herds See where the bison live and roam across The Nature Conservancy preserves in North America.

Prairie Predators

Historically, the bison's most important predator was the wolf. Wolves constantly followed the large herds singling out the old, incapacitated and very young animals. Even solitary adult males were not exempt from an attack—grizzly bears could kill an adult bison. Mountain lions and coyotes were also opportunistic predators of the young calves. Humans had their role to play too. The survival of many Native American tribes were closely tied to the bison herds.

Beyond predators and human activity, one of the primary dangers for bison herds were iced-over rivers. Thousands of bison drowned, particularly in the northern United States, when the crushing weight of crossing herds caused the ice to give way.

Since the wolf and grizzly bear are gone from the tallgrass prairies of the Great Plains region, humans must act as the predator. Each year, the herds are roundup into corrals to receive annual vaccinations, weight checks as well as managing the herd size by culling individual animals.

We know that you’re wondering and the answer is no, The Nature Conservancy has no plans to reintroduce wolves to the Tallgrass Prairie Preserve. It isn't big enough and they wouldn't mix well with our neighbors' cattle.

Bison calf laying in the grass.
Spring Brings New Life American Bison roam and graze the spring grasses across the more than 40,000 acre Tallgrass Prairie Preserve in Pawhuska, Oklahoma. © Morgan Heim
Bison mom and new calf soon after giving birth.
Bison calf at Tallgrass First bison calf of 2020 at Tallgrass Prairie Preserve © Harvey Payne

Watch the 1993 Bison Release

Take a trip in the Youtube time machine to watch a CBS news report covering the historic bison release featuring General Norman Schwarzkopf. 

Jump To Video

Returning Bison to the Tallgrass Prairie

In 1993 The Nature Conservancy reintroduced bison at the Joseph H. Williams Tallgrass Prairie Preserve as a critical part of restoration to the tallgrass prairie ecosystem. Preserve visitors can usually see one or more small groups of bison by driving the 15-mile bison loop. Still, they are wild animals with thousands of acres to roam and may be hidden by the rolling prairie terrain.

The Tallgrass Prairie Preserve bison herd began with 300 animals generously donated by the Ken-Ada Ranch north of Bartlesville named the Christina Adams Bison Herd in honor of the daughter of ranch owners Kenneth and Dianna Adams. This herd has since grown and lives on more than 30,000 acres. The herd size in the summer swells to approximately 2,700 animals that includes the calves born earlier in spring. After the annual roundup each fall the overwintering herd size is approximately 2,100 individuals.

Image from 1993 of the crowd watching as bison are released back on the prairie.
A large herd of bison heading out of fenced corrals with people looking on.
Bison on a pink and purple background of a speciality license plate.
Oklahoma Bison License Plate © Courtesy/Oklahoma Tax Commission

Join the Herd!

Support bison conservation in style with this colorful license plate!

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Managing The Herd

All young females who have not yet given birth, also known as 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, many efforts are taken to ensure the herd remains free from these diseases. During the annual roundup all keeper animals are vaccinated for several bovine diseases and treated for external and internal parasites.

Bulls (adult males) are sold at 6-7 years of age. Why? As they get older they become more aggressive and dangerous. Cows (adult females) are sold at 10-12 years of age. They are still productive through their early twenties but their sale value is higher as teenagers and as they age, they are less physically fit for withstanding the rigors of roundup.

Two adult male bison forcefully butting heads.
Bison at Tallgrass Prairie Bison sparring at Tallgrass Prairie Preserve in Oklahoma. © 2014 Morgan Heim for The Nature Conservancy
A full moon rises over the prairie and the bison herd.
American Bison A full harvest moon rises over the herd at Tallgrass Prairie Preserve, Pawhuska, Oklahoma. © Morgan Heim
Bison at Tallgrass Prairie Bison sparring at Tallgrass Prairie Preserve in Oklahoma. © 2014 Morgan Heim for The Nature Conservancy
American Bison A full harvest moon rises over the herd at Tallgrass Prairie Preserve, Pawhuska, Oklahoma. © Morgan Heim

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 natural creeks and ponds.

For research and good record-keeping, each individual animal in the herd is identified with an ear-tag transponder. This tag is read by holding a wand near the animal's head and the wand transmits the tag's data to a computer. Each transponder transmits a unique number, which is then assigned to that particular animal to track the animal's sex, origin, age, weight, pregnancy status and general health.

A person administers a vaccine to a bison by mouth.
Vaccination Bison at the Tallgrass Prairie Preserve at annually vaccinated against a variety of diseases. © David Smith

Bison Release - CBS - Oct 18, 1993 In the fall of 1993, 300 bison were released back to their home on the tallgrass prairie. And now it's time to celebrate many successful years of restoring a fully-functioning portion of the tallgrass prairie ecosystem with the use of free-roaming bison!