Animal
American bison
The American bison is a big, shaggy animal with a hump on its back. It lives in herds and eats grass on the prairie.
The American bison is the largest land animal in North America. Once tens of millions roamed the Great Plains, but by the 1890s fewer than a thousand were left. Careful protection, starting with a tiny herd in Yellowstone, brought bison back.
Bison bison is North America's largest land mammal, a grazing ruminant whose herds once shaped the continent's grasslands. Reduced to fewer than 1,000 animals by the 1890s, it has recovered to around 30,000 in conservation herds, yet wild, free-ranging bison remain rare and the IUCN lists it as Near Threatened.
Photo: Jack Dykinga, public domain, via Wikimedia Commons
Meet the American bison
The bison is a big, shaggy animal.
It has a big hump on its back and short, curved horns. It has a beard under its chin. It is the biggest land animal in North America.
The American bison is the biggest land animal in North America. A big bull can weigh about 900 kilograms and stand about 1.9 meters tall at his hump, taller than most grown-ups. Cows are about half that weight.
Bison have shaggy dark-brown fur on their heads, shoulders and front legs, a beard, and short horns that curve upward. Many people call them buffalo, but scientists prefer 'bison'. True buffalo, like the African buffalo, live on other continents.
Bison bison is the largest land mammal in North America. Bulls reach about 1.9 meters at the hump and 2.7 to 3.8 meters in length; cows are smaller. Both sexes carry short, upward-curving horns, and the long hair on the head, forequarters and forelegs contrasts with short, dense hair on the hindquarters.
Two subspecies are usually recognized, the plains bison and the wood bison of northern Canada, though DNA studies show they are one species and some biologists even include the European bison. The word 'buffalo' probably comes from the French 'boeuf' (beef); 'bison' is preferred scientifically because true buffalo are distant Old World relatives.
Quick facts
- Group
- Mammal
- Length
- 2.7 to 3.8 m
- Height
- 1.5 to 1.9 m
- Weight
- 500 to 900 kg
- Top speed
- up to 55 km/h
- Lifespan in the wild
- 15 to 20 years
Prairies, meadows and parks
Bison live in North America.
They live on wide, grassy lands called prairies. Some live in the mountains of Yellowstone, where winters are very snowy.
Before 1800, bison roamed across much of North America, with most of them on the Great Plains, a vast sea of grass between the Mississippi River and the Rocky Mountains. Some even lived in eastern forests.
Today most wild bison live in national parks and reserves in the United States and Canada. Yellowstone National Park is the only place in the United States where bison have lived wild ever since prehistoric times, through snowy winters of minus 40 degrees.
Historically, bison ranged across much of North America, with the greatest numbers on the Great Plains and some in forests east of the Mississippi. The IUCN now lists them as native and resident only in parts of Canada (including Alberta, British Columbia, Saskatchewan and the Northwest Territories) and of the United States (such as Montana, Wyoming, South Dakota and Utah), with reintroduced herds in Alaska and Mexico and none left in most former states.
Yellowstone's herd is the only one in the lower 48 states that has been free-ranging continuously since prehistoric times; its bison migrate up to about 110 kilometers between summer and winter ranges. Most other herds live within fences on public or private land. Shading on the map is by country, so it shows far more area than bison actually use.
Continent
Its habitat
Where can you find this animal?
- Lives here naturally · Countries and seas named by a scientific source
- Sightings recorded · Records of wild sightings (GBIF)
- Brought back by people · Countries and seas named by a scientific source
Lives here naturally · Countries and seas named by a scientific source
Parks, reserves and ranges in parts of western Canada and the United States, such as Yellowstone. Wild bison use only small, scattered areas of each country.
Places: Canada and United States.
Source: iucn-red-list · checked October 2026
Sightings recorded · Records of wild sightings (GBIF)
Counts of GBIF records of wild observations (human and machine) and preserved specimens. Records include introduced populations, vagrants, escaped or released animals and misidentifications, so a country with records is not necessarily part of the native range.
Wild sightings have been recorded in United States, Canada, Mexico, Germany, Denmark, Poland, Japan, Austria and 8 more places.
Source: gbif · checked October 2026
Brought back by people · Countries and seas named by a scientific source
Mexico, where the IUCN lists bison as extant and reintroduced (wood bison have also been reintroduced in Alaska, within the United States).
Places: Mexico.
Source: iucn-red-list · checked October 2026
Range maps show where scientists say an animal lives, often country by country. An animal may live in only part of a country shown, and sightings records can include animals that wandered far from home.
Grazers of the prairie
Bison eat grass.
They eat for many hours every day. In winter they sweep away snow with their heads to find the grass underneath.
Bison are grazers. In Yellowstone, grasses and grass-like plants called sedges make up more than 90 percent of what they eat, and they spend 9 to 11 hours a day feeding.
Like cows, bison are ruminants. They swallow grass, then later bring it back up to chew again, which is called chewing the cud. In winter, a bison swings its huge head from side to side like a snowplow to clear snow off the grass. Other hoofed animals usually dig with their feet instead.
Bison are bulk grazers: in Yellowstone, grasses and sedges make up more than 90 percent of the diet, with forbs and browse usually under 5 percent, and foraging takes 9 to 11 hours a day. As ruminants with a multi-chambered stomach, they alternate feeding with regurgitating and rechewing cud, so microbes can break plant fiber into fatty acids. The NPS reports that their large digestive tract handles low-quality forage more efficiently than cattle, deer or elk.
Bison also engineer their food supply. Rather than following the spring 'green wave' of new growth, Yellowstone bison return to graze the same areas repeatedly, which keeps plants growing short and nutritious.
Did you know?
Birds ride on bison.
Magpies perch on bison to pick insects from their coats, and cowbirds follow them to catch insects stirred up by their hooves.
Magpies glean insects from bison coats, and cowbirds follow herds to catch insects flushed by their movement.
Built for winter
A bison's hump is made of strong muscles.
Its thick, woolly coat keeps it warm in the snow. Bison can run fast and jump high, even though they are so big.
A bison's hump is not fat. It is made of strong muscles attached to long bones in the back. These muscles let a bison swing its big head to push away snow.
Bison stay warm with thick skin, a woolly underfur, long outer hairs and layers of fat. Bison are also surprisingly athletic: they can run at about 55 km/h, jump over things about 1.5 meters high, and swim across rivers.
The shoulder hump is muscle anchored to long spinous processes of the thoracic vertebrae, powering the side-to-side head sweep used to clear snow. Insulation comes from thick skin, dense underfur, long guard hairs and fat reserves, which together let bison survive winters in which temperatures can fall to around minus 42 degrees Celsius.
Despite their bulk, bison are agile: the NPS reports running speeds of about 55 km/h, rapid pivots, jumps of about 1.5 meters and strong swimming. Their hearing and sense of smell are excellent; the NPS also rates their vision highly, though the Smithsonian says bison do not see very well. Bulls have broader, more triangular heads, thicker fur on the forehead and forelegs, and shoulders broader than their hips; cows have slimmer, more curved horns.
Red calves of spring
A baby bison is called a calf.
It is born in spring with reddish fur. Within a few hours it can keep up with the herd. Its fur turns brown as it grows.
Bison calves are born in late April and May, after their mothers have been pregnant for about nine months. A calf weighs about 20 kilograms and has bright reddish-tan fur.
Just two or three hours after birth, a calf can keep up with the herd. Its mother and the other bison protect it. Its coat starts turning brown at about two and a half months, and it drinks milk for seven or eight months.
After a gestation of 9 to 9.5 months (about 285 days), single calves are born in late April and May, weighing about 20 kilograms. They are reddish-tan and begin darkening at about 2.5 months. Calves keep pace with the herd within two to three hours, nurse for seven to eight months and are fully weaned by the end of the first year.
First winters are hard: the NPS reports that 20 to 40 of every 100 first-year Yellowstone bison may die from accidents, cold or predation, compared with about 9 in 100 adults. Bison mature sexually at about two, but bulls older than seven sire most calves. Life expectancy is about 15 to 20 years.
Herds, wallows and the rut
Bison live in herds.
They roll in the dust to get rid of bugs. In summer, the big males bellow very loudly. Bison stand together to stay safe.
Bison live in herds that seem to be led by older females. In Yellowstone, herds average about 20 animals in winter and about 200 in summer, and up to around 1,000 gather in July and August for the mating season, called the rut. Then the bulls bellow loudly, roll in the dust and push each other to show who is strongest.
Rolling in dusty hollows, called wallowing, keeps biting flies away. Bison are big and fast, so in parks people stay well back from them.
Herds of cows, calves and young bulls appear to be directed by older females; mature bulls live alone or in small bachelor groups outside the rut. Group sizes in Yellowstone average about 20 in winter and 200 in summer, with up to about 1,000 during the July-August rut, when bulls bellow, wallow and fight for access to cows.
Wallowing deters biting insects, sheds molted fur and spreads scent. Wolves and grizzly bears are the only large predators of adults, and bison usually face attackers as a group, which makes them hard targets. Birds such as magpies pick insects from their coats. In parks, visitors must keep a long distance, because bison are wild and can move quickly.
Did you know?
Bison use their heads like snowplows.
In winter, a bison swings its big head from side to side to sweep snow off the grass.
Neck and hump muscles let bison clear snow by sweeping the head sideways, unlike most hoofed animals that paw with their feet.
A great comeback
Long ago, bison almost disappeared.
People saved the last few and protected them. Now there are many more bison in parks again.
There may once have been 30 to 60 million bison in North America. In the 1800s, huge numbers were killed for their hides and meat, and the U.S. Army set out to wipe out the bison as a way to control the Plains tribes who depended on them. By the 1890s, fewer than 1,000 were left.
In Yellowstone, about two dozen wild bison survived in 1902. Protecting them, and adding bison from private herds, rebuilt the population. Today about 30,000 bison live in conservation herds across North America.
Estimates of bison numbers before the mid-1800s range from 30 to 60 million (NPS) or more. Market hunting and a U.S. Army campaign to eliminate bison as a way to control the Plains tribes who depended on them reduced them to fewer than 1,000 by the 1890s; Yellowstone's wild herd fell to about two dozen by 1902 before protection and 21 bison from private herds rebuilt it. Yellowstone held nearly 5,300 bison in 2025.
About 30,000 bison now live in conservation herds, while several hundred thousand are raised as livestock and do not count toward wild numbers. The IUCN lists the species as Near Threatened; its Green Status of Species rates it 'Critically Depleted', a measure of how far it remains from full ecological recovery. Free-ranging herds are few. The National Park Service works with federal, state and tribal agencies on where bison may roam outside Yellowstone, one of the park's most complex conservation issues.
IUCN Red List
How is the american bison doing in the wild?
- Least Concern
- Near Threatened (this animal)
- Vulnerable
- Endangered
- Critically Endangered
- Extinct in the Wild
- Extinct
Near Threatened
Not at risk yet, but it could be soon.
See the IUCN Red List assessment · The IUCN Red List of Threatened Species 2022.2
Amazing facts
-
Bison use their heads like snowplows.
In winter, a bison swings its big head from side to side to sweep snow off the grass.
Neck and hump muscles let bison clear snow by sweeping the head sideways, unlike most hoofed animals that paw with their feet.
-
Baby bison have red fur.
Bison calves are born reddish-tan and start turning brown at about two and a half months.
Calves are reddish-tan at birth and begin darkening at about 2.5 months of age.
-
Bison can run fast and jump high.
A bison can run at about 55 km/h and jump over things about 1.5 meters high.
Despite weighing up to about 900 kilograms, bison can run about 55 km/h, pivot quickly and clear obstacles about 1.5 meters high.
-
Birds ride on bison.
Magpies perch on bison to pick insects from their coats, and cowbirds follow them to catch insects stirred up by their hooves.
Magpies glean insects from bison coats, and cowbirds follow herds to catch insects flushed by their movement.
Words to know
- prairie
- a large, flat or rolling grassland
- herd
- a large group of animals that live and move together
- ruminant
- an animal that brings up its food to chew again, called chewing the cud
- wallow
- to roll in dust or mud; also the hollow made by rolling
- rut
- the mating season, when males compete
- conservation herd
- a group of animals kept to protect the species, not for farming
Discovery challenge
-
What is a bison's hump made of?
What is a bison's hump made of?
What does the bison's hump allow it to do?
- Water
- Strong muscles
- Fat only
Show the answer
Strong muscles
The hump is made of strong muscles.
The hump is muscle attached to long back bones, which lets the bison swing its head to clear snow.
Muscle on long vertebral spines powers the side-to-side head sweep used to clear snow from grass.
-
What color is a baby bison?
What color are bison calves when they are born?
When do bison calves begin to darken?
- Reddish
- Bright blue
- White with spots
Show the answer
Reddish
Baby bison are reddish when they are born.
Calves are reddish-tan and start turning brown at about two and a half months.
At about 2.5 months the reddish-tan calf coat starts turning brown.
-
What do bison eat?
What makes up most of a bison's food?
Which describes the bison diet in Yellowstone?
- Grass
- Fish
- Fruit
Show the answer
Grass
Bison eat grass.
Grasses and sedges make up more than 90 percent of what Yellowstone bison eat.
Over 90 percent graminoids (grasses and sedges), with forbs and browse usually under 5 percent.
-
Were bison almost all gone once?
About how many bison were left by the 1890s?
Roughly how many wild bison remained in Yellowstone in 1902?
- Fewer than 1,000
- About 10 million
- More than ever
Show the answer
Fewer than 1,000
Yes! Very few were left, but people saved them.
Fewer than 1,000 bison were left by the 1890s. Protection brought them back.
About two dozen; for the whole continent, fewer than 1,000 bison remained by the 1890s.
Places where you might see it
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Watch
Natural wonder
Yellowstone National Park
Yellowstone National Park sits on top of a giant volcano in the western United States. Heat from melted rock deep underground powers more than 10,000 hot springs, geysers, mudpots and steam vents, and the park is home to bison, wolves and two kinds of bears.
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Watch
Country
United States
The United States is a large country in North America made of 50 states, from icy Alaska to the warm islands of Hawaii. It has the Grand Canyon, the Mississippi River and Yellowstone, and about 342 million people live there.
Experiments to try
- Watch What If? Lab What if forests became grasslands? Forests and grasslands are next-door neighbors in many places, and fire, grazing animals and rain decide where one ends and the other begins. Imagine a forest becoming a grassland: who would move in, what would happen to the soil, and where would all the carbon in the trees go?
- Watch What If? Lab What if a forest grew back after a fire? In 1988, fires passed through about a third of Yellowstone National Park. Today, the young trees that sprouted afterward have grown into new forests. Follow the forest's comeback: the first plants, the pine cones that open with heat, and the animals that return.
Explore next
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African buffalo
The African buffalo is a huge, cow-like grazer with heavy, curving horns. It lives in herds that can number in the thousands, and a herd will rush to protect a calf in danger. It lives across much of Africa south of the Sahara, from open savannas to rainforests.
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Black-tailed prairie dog
Black-tailed prairie dogs are sociable ground squirrels of North America's Great Plains. They dig huge underground towns, keep the grass short to watch for danger, and bark warnings to each other. Many other animals depend on their towns.
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3D
Animal
Gray wolf
The gray wolf is the largest member of the dog family and the wild ancestor of pet dogs. Wolves live in family packs that hunt big animals like elk and moose together, and their howls can carry about 10 kilometers. After being wiped out in many places, wolves are coming back in parts of North America and Europe.
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Watch
Animal
Moose
The moose is the largest member of the deer family. It lives in northern forests, wades and even dives into lakes to eat water plants, and bull moose grow enormous new antlers every year. In Europe it is called an elk.
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Animal
Muskox
Muskoxen are shaggy Arctic grazers with long coats that nearly reach the ground and a super-warm underwool called qiviut. Herds protect their calves by standing in a ring with their horns facing out. Despite the name, they are more closely related to goats and sheep than to oxen.
- Watch What If? Lab What if forests became grasslands? Forests and grasslands are next-door neighbors in many places, and fire, grazing animals and rain decide where one ends and the other begins. Imagine a forest becoming a grassland: who would move in, what would happen to the soil, and where would all the carbon in the trees go?
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Watch
3D
Animal
Saiga antelope
The saiga antelope is a goat-sized antelope with an amazing floppy nose. Huge herds roam the dry steppes of Central Asia. Saigas were once nearly wiped out by hunting, but thanks to protection there are now more than a million.
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Watch
3D
Animal
Cattle
Cattle are large farm animals that people tamed from wild oxen long ago. They eat grass and digest it with a stomach that has four parts. Farmers around the world keep cattle for milk, meat and leather, and in some places oxen still pull plows and carts.
For parents & teachers
What children will learn
- Describe how the bison's hump, coat and digestion help it survive grassland winters.
- Explain what a ruminant is and how bison graze.
- Describe the bison life cycle and herd life.
- Explain the history of the bison's near extinction and recovery, including its impact on Plains peoples.
Recommended ages: 3 to 17 · About 15 minutes
Talk about it
- Why might killing the bison have harmed the people who depended on them?
- Yellowstone's bison grew from about two dozen animals. What do you think helped them recover?
- Why do park rangers ask visitors to stay far away from bison?
Try at home or in class
- Measure 1.9 meters up a wall with tape to see how tall a bull bison stands at his hump.
- Wrap one cup of warm water in a wool sock and leave another bare: after 20 minutes, feel which stayed warmer, like a bison in its winter coat.
Key vocabulary: prairie, herd, ruminant, wallow, rut, conservation herd
Where these facts come from
- The IUCN Red List of Threatened Species , International Union for Conservation of Nature (IUCN terms of use (no redistribution of Red List data or range maps))
- GBIF Backbone Taxonomy and GBIF Occurrence Search , Global Biodiversity Information Facility (CC0 1.0 (backbone); occurrence counts are facts derived from records under CC0, CC BY and CC BY-NC)
- Bison Ecology , National Park Service, Yellowstone National Park
- American bison , Smithsonian's National Zoo and Conservation Biology Institute
- Bison bison (American bison), 2016 assessment , IUCN Red List
- Wikidata , Wikimedia Foundation (CC0 1.0)
- Wikimedia Commons , Wikimedia Foundation (Per file: Public domain, CC0, CC BY or CC BY-SA only (credited on each page))
Checked, not yet human-reviewed. Last updated October 28, 2026. Spotted a mistake? Tell us.