15 Facts About Our National Mammal: The American Bison

The American bison was named the national mammal of the United States on May 9, 2016. This majestic animal joins the ranks of the Bald Eagle as the official symbol of our country—and much like the eagle, they’re a symbol of our American identity and one of the greatest conservation success stories of all time. 

In prehistoric times, millions of bison roamed North America—from the forests of Alaska and the grasslands of Mexico to Nevada’s Great Basin and the eastern Appalachian Mountains. Their history has been inextricably intertwined with many Indigenous communities. But by the late 1800s, there were only a few hundred bison left in the United States after European settlers pushed west, reducing the animal’s habitat and hunting the bison to near extinction. Had it not been for a few private individuals working with Tribes, states and the Department of the Interior, the bison would be extinct today.  

Explore more fun facts about the American bison: 

1. Bison are the largest mammal in North America. Male bison (called bulls) weigh up to 2,000 pounds and stand 6 feet tall, while females (called cows) weigh up to 1,000 pounds and reach a height of 4-5 feet. Bison calves weigh 30-70 pounds at birth. 


Bison at Rocky Mountain Arsenal National Wildlife Refuge in Colorado.

2. Since the late 19th century, Interior has been the primary national conservation steward of the bison. Public lands managed by Interior support 17 bison herds—or approximately 10,000 bison—in 12 states, including Alaska. This is about one-third of all wild bison in North America.


A bison calf between two adults.

3. What’s the difference between bison and buffalo? While bison and buffalo are used interchangeably, in North America the scientific name is bison. Actually, it’s Bison bison bison (genus: Bison, species: bison, subspecies: bison or athabascae), but only saying it once is fine. Historians believe the term “buffalo” grew from the French word for beef, “boeuf.”


A resting bison at Wichita Mountains National Wildlife Refuge.

4.Yellowstone National Park is the only place in the U.S. where bison have continuously lived since prehistoric times. What makes Yellowstone’s bison so special is that they’re the descendants of early bison that roamed our country’s grasslands. In 2021, Yellowstone’s bison population was estimated at 5,450—making it the largest bison population on public lands. This population is allowed to roam relatively freely over the expansive landscape of Yellowstone National Park and some nearby areas of Montana.


Eight bison walking by the Grand Prismatic Spring.

5. What’s a “red dog”? It’s a baby bison. Bison calves tend to be born from late March through May and are orange-red in color, earning them the nickname “red dogs.” After a few months, their hair starts to change to dark brown and their characteristic shoulder hump and horns begin to grow.


A bison and calf at Rocky Mountain Aresenal National Wildlife Refuge in Colorado

6. The history of bison and Native Americans are intertwined. Bison have been integral to Tribal culture, providing them with food, clothing, fuel, tools, shelter and spiritual value. Established in 1992, the Inter Tribal Buffalo Council works with the National Park Service to transfer bison from national park lands to Tribal lands.


The Bison Range in Montana.

7. You can judge a bison’s mood by its tail.  When it hangs down and switches naturally, the bison is usually calm. If the tail is standing straight up, watch out! It may be ready to charge. No matter what a bison’s tail is doing, remember that they are unpredictable and can charge at any moment. Every year, there are regrettable accidents caused by people getting too close to these massive animals. It’s great to love the bison but love them from a distance.


A bison watching over a calf at Yellowstone National Park.

8. Wind Cave National Park’s herd helped revive bison populations around the country. The story starts in 1905 with the formation of the American Bison Society and a breeding program at the New York City Zoo (today, the Bronx Zoo). By 1913, the American Bison Society had enough bison to restore a free-ranging bison herd. Working with Interior, they donated 14 bison to Wind Cave National Park in South Dakota. More than 100 years later, the bison from Wind Cave have helped reestablishing other herds across the United States and most recently in Mexico.


A small herd of bison at Wind Cave National Park in South Dakota.

9. Bison may be big, but they’re also fast. They can run up to 35 miles per hour. Plus, they’re extremely agile. Bison can spin around quickly, jump high fences and are strong swimmers.


A bison charging through a river at Yellowstone National Park.

10. Pass the salad, please. Bison primarily eat grasses, weeds and leafy plants—typically foraging for nine to 11 hours a day. That’s where the bison’s large protruding shoulder hump comes in handy during the winter. It allows them to swing their heads from side-to-side to clear snow—especially for creating foraging patches. Learn how bison's feeding habits can help ensure diversity of prairie plant species especially after a fire.


Bison in the snow at Yellowstone National Park.

11. From hunter to conservationist, Teddy Roosevelt helped save bison from extinction. In 1883, Teddy Roosevelt traveled to the Dakota Territory to hunt bison. After spending a few years in the west, Roosevelt returned to New York with a new outlook on life. He paved the way for the conservation movement, and in 1905, formed the American Bison Society with William Hornaday to save the disappearing bison. Today bison live in all 50 states, including Tribal lands, wildlife refuges, national parks and private lands.


A bison stands alone in Theodore Roosevelt National Park in North Dakota.

12. Bison can live up to 20 years old. The average lifespan for a bison is 10–20 years, but some live to be older. Cows begin breeding at the age of two and only have one baby at a time. For males, the prime breeding age is six to 10 years. Learn how Interior works to ensure genetic diversity and long-term viability of bison.


Bison herd on the move.

13. A little dirt won’t hurt. Called wallowing, bison roll in the dirt to deter biting flies and help shed fur. Male bison also wallow during mating season to leave behind their scent and display their strength.

A bison rolling around in the dirt. Photo by Jim Peaco, National Park Service.

14. The American bison’s ancestors can be traced to southern Asia thousands of years ago. Bison made their way to America by crossing the ancient land bridge that once connected Asia with North America during the Pliocene Epoch, some 400,000 years ago. These ancient animals were much larger than the iconic bison we love today. Fossil records show that one prehistoric bison, Bison latiforns, had horns measuring 9 feet from tip to tip.


Bison standing in the snow at the National Elk Refuge in Wyoming.

15. Bison are nearsighted -- who knew? While bison have poor eyesight, they have excellent senses of smell and hearing. Cows and calves communicate using pig-like grunts, and during mating season, bulls can be heard bellowing across long distances.


A bison checking out a park information sign at Wind Cave National Park.

The Department of the Interior collaborates with other federal, Tribal, state and conservation partners to restore large, wild bison herds on appropriate large landscapes to manage bison as native wildlife, and to strengthen cultural connections of Native American peoples and the American public to our national mammal. We hope you’ve enjoyed these fun facts about this amazing animal!