“American bison are the biggest land animals in North America, and big bulls can weigh as much as a small car.”
American bison are large grazers that shape North American prairies through herd movement, close-cropping of grasses, and dust wallows. Wild populations recovered from near-collapse but remain fragmented across protected and managed lands.
By An Nguyen · Published · Updated
Browse photographs of american bison across habitat, behavior, anatomy, and life stages.
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Core article
A closer look at habitat, diet, behavior, reproduction, and conservation.
The American bison (Bison bison) is the largest land animal in North America and the shaggy icon of its grasslands. Built for hard winters, open distances, and wolves, this herbivore is a keystone engineer of the prairie — its grazing, trampling, and wallowing shape the whole plant community. Its story also runs through near-extinction in the 1800s and a hard-won recovery since.
Bulls can reach 12.5 feet long, stand 6.5 feet at the shoulder, and weigh up to about 2,200 pounds; cows are smaller, up to roughly 1,000. The defining feature is the shoulder hump — not fat like a camel's, but muscle anchored on elongated vertebrae, powering the head as the animal sweeps snow aside to reach dormant grass beneath. Its coat is a survival system: a dense woolly undercoat under coarse guard hairs insulates so well that snow can settle on its back without melting. In spring the winter coat sheds in ragged clumps. Both sexes carry short curved horns, never shed, used against predators and, among bulls, in the rut. The species sits in the cattle family Bovidae and includes two subspecies — the plains bison and the larger northern wood bison.
Bison once held the largest range of any North American herbivore — from Alaska and Canada down through the central plains into northern Mexico, and east to the Appalachians — in herds of tens of millions. Today the range is a fraction of that and heavily fragmented, with most animals in national parks, state reserves, and private ranches across the U.S. and Canada. Plains bison hold the open grasslands of the midwest and southern Canada; wood bison keep to northern boreal forest and muskeg. Their selective grazing knocks back dominant grasses and lets wildflowers and forbs flourish, raising prairie diversity. They share this open country with the smaller, faster pronghorn.
Bison are ruminant grazers built for tough, low-grade forage — mostly grasses and sedges, with some wildflowers, lichens, and shrubs. A wide, flat muzzle crops vegetation close to the ground, and they feed unselectively across large areas. Their four-chambered stomach ferments the fibre with the help of gut microbes, and they regurgitate and re-chew the cud to break down cell walls. This lets bison extract a living from the silica-rich prairie grasses that non-ruminant grazers cannot survive on.
Bison society is fluid and, for much of the year, split by sex: cows, calves, and young form maternal bands, while bulls travel alone or in small bachelor groups, the bands merging into big aggregations on the move to fresh grass or water. A signature behavior is wallowing — rolling hard in dust and mud, which deters biting insects, helps shed the winter coat, and leaves scent that signals status. In the midsummer rut, bulls rejoin the herds and compete with deep bellowing and head-to-head charges, thick skulls and humped shoulders absorbing collisions that can still break bone.
Breeding timing is tuned to the seasons. After about 285 days' gestation, a cow bears a single calf in spring, as nutrient-rich new grass emerges. Newborns lack the hump and wear a bright orange-red coat — "red dogs" — and can stand, walk, and run within hours, essential against wolves and grizzlies. Calves nurse seven to eight months, their coats darkening to adult chocolate-brown over the first year as the hump develops. Bison mature at two to three years and live 15 to 20 in the wild, sometimes 25 in captivity.
The IUCN lists the bison as Near Threatened — a status that carries its recent history. In the 1800s, commercial hunting, railroad expansion, and deliberate campaigns to starve Plains tribes cut the population from an estimated 30–60 million to fewer than 1,000 by the 1890s. Early conservationists and ranchers pulled it back, and about 500,000 now live in North America — but most are raised as livestock and carry trace cattle DNA from historical crossbreeding. The pressing issues today are genetic diversity, disease (bovine brucellosis fuels conflict and culling around Yellowstone), and the shortage of large, connected prairie where diverse herds can roam and resume their role as ecosystem engineers.
Kingdom
Animalia
Phylum
Chordata
Class
Mammalia
Order
Artiodactyla
Family
Bovidae
Genus
Bison
Species
B. bison
American bison are the biggest land animals in North America, and big bulls can weigh as much as a small car.
Newborn calves are orange-red, so people nickname them 'red dogs.'
Despite their size, bison can run up to 35 miles per hour and jump surprisingly high.
Bison roll in dust and dirt, called wallowing, to clean their coats and shoo away bugs.
In winter, a bison swings its head from side to side to clear snow and reach the grass below.
In 2016 the American bison became the official national mammal of the United States.
Select a question to reveal the answer.
An American bison is a large, shaggy, humped grazing mammal from North America. It is the continent's biggest land animal and lives in herds on grasslands and prairies.
Bison live on the grasslands, prairies, and river valleys of North America. Today most live in protected parks, refuges, and managed herds in the United States and Canada.
Bison are herbivores. They mostly eat grasses and sedges, spending many hours each day grazing and then chewing their cud like cows do.
People often call them 'buffalo,' but true buffalo live in Africa and Asia. The American bison is a different animal, even though the nickname has stuck for a long time.
In the 1800s, intensive hunting reduced bison numbers from tens of millions to only a few hundred. Conservation efforts later helped them recover.
Adult bulls can stand about 6 feet tall at the shoulder and weigh up to roughly 2,000 pounds, making them the largest land mammals in North America.
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