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6–6.5 feet (1.8–2.0 m)
Height (Males)
1,500 to 2,000 lbs (680–900 kg)
Weight (Males)
5 feet (1.5 m)
Height (Females)
800 to 1,100 lbs (360–500 kg)
Weight (Females)

About

#Mammals

The American Bison (Bison bison), often referred to as the buffalo of the North American plains, is an iconic symbol of the American frontier and one of the most remarkable land mammals in the Western Hemisphere. It belongs to the family Bovidae, which also includes antelope, cattle, goats, and sheep. The bison is the largest terrestrial mammal in North America, and it once roamed the continent in vast herds, shaping both ecosystems and Indigenous cultures across the Great Plains.

There are two recognized subspecies: the plains bison (Bison bison bison), which historically occupied the grasslands from Canada to Mexico, and the wood bison (Bison bison athabascae), found primarily in the boreal forests of Canada and Alaska. While similar, wood bison are larger and have squarer humps and longer legs, suited for moving through deep snow and forest terrain.

American Bison are powerfully built animals, characterized by their massive shoulder hump, thick shaggy forequarters, and sturdy legs. Mature males (bulls) can weigh up to 2,000 pounds (900 kg) and stand over 6 feet (1.8 meters) tall at the shoulder, while females (cows) are smaller but still formidable. Their thick coat, ranging from dark brown to almost black, insulates them from both summer heat and frigid winters.

Bison are herd animals, often moving in groups that range from small family units to massive aggregations. They are primarily grazers, feeding on grasses, sedges, and other low vegetation. Despite their size, they are agile and capable of running up to 35 miles per hour (56 km/h), jumping high fences, and swimming across rivers.

Once nearly driven to extinction due to overhunting and habitat loss, the American Bison has rebounded through dedicated conservation efforts, especially in national parks, tribal lands, and private preserves. Today, it stands not only as a biological marvel but also as a symbol of cultural resilience and ecological restoration in North America.

Threatened:
Extinct
Critically Endangered
Endangered
Vulnerable
Near Threatened
Least Concern

Physical Characteristics

The American Bison is a massive, powerfully built ungulate and the largest land mammal in North America. Its formidable size, muscular build, and distinct features have made it one of the most iconic animals of the Great Plains and boreal forests.

Size and Weight
Adult bison display significant sexual dimorphism:

  • Males (bulls) can weigh 1,500 to 2,000 pounds (680–900 kg) and stand 6–6.5 feet (1.8–2.0 meters) at the shoulder.

  • Females (cows) are smaller, weighing 800 to 1,100 pounds (360–500 kg) and standing around 5 feet (1.5 meters) tall.

The length of a mature bison ranges from 7 to 12.5 feet (2.1–3.8 meters) from nose to tail tip.

Hump and Body Shape
One of the most distinctive features is the prominent shoulder hump, formed by elongated vertebrae and massive shoulder muscles. This gives the bison its signature sloped back and immense digging and snow-plowing strength—especially important in winter feeding.

Coat and Coloration
Bison have a thick, woolly coat of coarse hair:

  • The front half is covered in dense, shaggy fur, especially around the shoulders, neck, and head.

  • The hindquarters have shorter, sparser hair.

  • Coat color ranges from dark brown to almost black, though it may lighten slightly in summer.

The coat is shed annually in late spring or early summer, with tufts often peeling off in large clumps.

Head and Horns
Bison have a broad, rounded head with a short, curved pair of black horns found on both sexes. Horns typically grow up to 2 feet (60 cm) in length, arching outward and then upward. These horns are used in defense, mating battles, and establishing dominance.

Their eyes are small and dark, set well apart to provide panoramic vision, and their ears are short and partially hidden in the mane.

Legs and Hooves
Despite their bulk, bison have short, muscular legs with cloven hooves that support rapid acceleration, agile turns, and strong endurance. They can run at speeds up to 35 mph (56 km/h) and jump over 6-foot (1.8-meter) obstacles.

In sum, the American Bison’s powerful body, dense coat, iconic hump, and sturdy horns all contribute to its survival in harsh environments and its dominance on the North American plains.

Reproduction

The reproductive cycle of the American Bison is seasonal and structured around the rhythms of the North American prairie, with calves born in spring to coincide with the most abundant food resources. Bison exhibit a polygynous mating system, where dominant males compete for breeding access to multiple females during a well-defined rutting season.

Breeding Season (Rut)
The bison rut occurs in late summer, typically from July through September. During this time, bulls join female herds, where they engage in ritualized competition for mating rights. Dominant bulls display their fitness through:

  • Roaring bellows and low grunts

  • Pawing the ground and wallowing in dust

  • Head swinging and physical posturing

  • Occasional horn clashes with rival bulls

These displays can escalate into fierce, though usually non-lethal, battles that determine breeding hierarchy.

Mating and Fertilization
Once dominant bulls establish control over receptive females, mating occurs. Bulls will guard individual females (tending bonds) for several days, following and protecting them from rivals until mating is complete.

Gestation and Calving
The gestation period lasts about 270–285 days (approximately 9 months). Most calves are born between April and May, when new grass growth provides vital nutrition for nursing mothers and growing calves.

Birth and Early Life
Females give birth to a single calf (twins are very rare), usually in isolation from the herd for safety. Calves are precocial—able to stand and walk within an hour—and are reddish-golden in color at birth, earning them the nickname “red dogs.” Their coat darkens over the first few months.

Calves nurse for 4 to 6 months, though they begin grazing as early as a few weeks old. They typically remain close to their mothers through the first year.

Sexual Maturity and Breeding Age

  • Females reach sexual maturity by 2–3 years of age and may breed annually thereafter.

  • Males reach sexual maturity around the same time but typically do not breed successfully until 6 years or older, once they can compete for dominance.

The reproductive strategy of the bison ensures synchronized calving, maximized calf survival, and long-term population sustainability in wild and managed herds.

Lifespan

The American Bison is a long-lived mammal, particularly for a wild ungulate, with individuals often surviving well over a decade in natural settings and significantly longer in managed environments. Lifespan is influenced by habitat conditions, predation, human activity, and access to veterinary care in captivity.

In the Wild
In natural settings such as national parks, reserves, or large conservation herds, bison commonly live 12 to 15 years, with some individuals reaching up to 20 years.

  • Females tend to live longer than males, as bulls expend more energy during the breeding season and are more prone to injury from fights or rut-related stress.

  • Calves have a higher mortality rate during their first year, mainly due to predation (by wolves, bears, or coyotes) or environmental extremes.

In Captivity or Protected Reserves
In zoos, wildlife preserves, and private ranches, where threats from predators, disease, and harsh winters are reduced, bison may live 20 to 25 years, with some females recorded at over 30 years of age. Access to consistent food, shelter, and veterinary care significantly extends lifespan.

Age-Related Changes
As bison age, they may exhibit:

  • Worn teeth, reducing foraging efficiency

  • Reduced fertility, especially in older cows

  • Slower movement and diminished dominance in bulls, eventually leading them to be pushed out of breeding hierarchies

Older bulls often live alone or on the edges of herds, while older cows may remain integrated with female groups.

Reproductive Longevity
Females can remain reproductively active into their late teens, although calving intervals may increase and calf survival may decline with age. Bulls tend to lose breeding competitiveness after about 10 to 12 years.

In summary, the American Bison has a substantial lifespan for a grazing mammal, supporting a long reproductive window and multigenerational herd dynamics, especially in stable or protected populations.

Eating Habits

The American Bison is a specialized grazer, feeding primarily on grasses and sedges across the prairies, plains, and open woodlands of North America. Its eating habits play a critical role in shaping the ecosystems it inhabits, making it a keystone herbivore in grassland environments.

Primary Diet
Bison consume a wide range of grasses, sedges, and other herbaceous plants, with seasonal variation depending on availability:

  • In spring and summer, they favor young, green grasses that are high in protein and moisture—species like blue grama, buffalo grass, and big bluestem.

  • In winter, when snow covers the ground and green vegetation is scarce, they shift to dry grasses and sedges, digging through snow with their massive heads and shoulders to access forage.

Unlike browsers such as deer or moose, bison rarely eat woody shrubs or tree leaves, though they may occasionally consume forbs (flowering herbs) and low shrubs when grass is limited.

Foraging Behavior
Bison spend 8–11 hours per day grazing, often divided between early morning and late afternoon sessions, with periods of rest and rumination in between. They graze with their heads low, sweeping side to side as they crop vegetation with their large, flat teeth.

They are highly mobile and will travel great distances in search of quality forage, often shaping plant communities through their movement patterns and selective grazing.

Digestive System
Like all bovids, bison are ruminants, meaning they have a four-chambered stomach that allows them to ferment and break down tough plant material. This system supports efficient extraction of nutrients from fibrous grasses and helps them survive on low-quality forage during harsh winters.

Ecological Role
Bison grazing helps:

  • Maintain open prairie ecosystems

  • Promote plant diversity by preventing overdominance of certain grass species

  • Enrich soil through manure and trampling, stimulating seed dispersal and nutrient cycling

In summary, the American Bison’s eating habits reflect its evolutionary adaptation to open grasslands, where its grazing behavior shapes both the land and the lives of countless other species.

Uniqueness

The American Bison is a symbol of resilience and ecological power, uniquely adapted to the grasslands and woodlands of North America. Its size, history, behavior, and ecological role make it one of the most remarkable and iconic mammals of the Western Hemisphere.

Largest Land Mammal in North America
No other native land mammal rivals the bison’s sheer mass and presence. Bulls can weigh up to 2,000 pounds (900 kg), yet they remain agile, capable of running 35 mph (56 km/h), leaping fences, and swimming rivers. This rare combination of strength, speed, and endurance is unmatched among North American herbivores.

Distinctive Physical Features
The bison’s massive shoulder hump, shaggy front coat, and short, curved black horns give it a prehistoric appearance—echoing its Ice Age ancestors. Its hump contains specialized vertebrae and muscle for plowing snow and defending against predators, while its dark facial mask and sweeping head movements are unmistakable.

Keystone Grazer and Ecosystem Shaper
Bison are keystone species—their selective grazing shapes plant communities, maintains grassland health, disperses seeds, recycles nutrients, and creates habitats for insects, birds, and other wildlife. Wallows they create (shallow depressions formed by dust-bathing) become microhabitats for water retention and biodiversity.

Cultural and Historical Significance
No other animal is as deeply woven into the cultural identity of Indigenous peoples, who relied on bison for food, clothing, shelter, and spiritual symbolism. The bison is also the national mammal of the United States, representing recovery from near extinction.

Conservation Comeback
Once numbering 30–60 million, bison were driven to the brink of extinction in the 19th century, with fewer than 1,000 remaining by the 1880s. Today, thanks to conservation efforts, national parks, tribal leadership, and private stewardship, the American Bison has rebounded to over 500,000 individuals—a profound story of ecological and cultural restoration.

From its awe-inspiring presence and powerful ecological role to its deep cultural roots and dramatic comeback, the American Bison remains one of the most unique and enduring symbols of wild North America.

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FAQ’s

1. What is the species closest to the American Bison?

The species most closely related to the American Bison (Bison bison) is the European Bison (Bison bonasus), also known as the wisent. Both belong to the genus Bison and share a common ancestor that lived during the late Pleistocene.

While they differ in habitat and some physical traits—European bison are slightly taller and less heavily built—the two species are genetically similar and are the only surviving members of their genus. A more distant relative is domestic cattle (Bos taurus), with whom bison can interbreed to produce hybrids known as beefalo.

2. How do American Bison compare to other buffalos?

The American Bison is often colloquially called a “buffalo,” but true buffaloes belong to different genera entirely:

Feature American Bison (Bison bison) African Buffalo (Syncerus caffer) Asian Water Buffalo (Bubalus bubalis)
Native Range North America Sub-Saharan Africa South and Southeast Asia
Horns Short, curved, upward Broad, curled outward then inward Long, crescent-shaped, swept back
Shoulder Hump Prominent Absent Minimal
Hair Thick, shaggy forequarters Sparse Sparse
Domesticated? No (though ranch-managed) No Yes, widely domesticated
Temperament Generally non-aggressive but powerful Very aggressive and dangerous Domesticated form is docile; wild form is dangerous

Overall, the American Bison is more cold-adapted, has a distinctive shoulder hump, and is genetically and taxonomically closer to cattle than to true buffaloes. Despite the name “buffalo,” it is not a true buffalo at all.

3. What national parks provide the greatest chances to see Bison?

The American Bison can be found in both Canada and the United States.  Here are the national parks where you have the greatest chances to see Bison:

🇺🇸 United States

  • Yellowstone National Park (Wyoming, Montana, Idaho) – Home to the largest free-roaming, genetically pure herd of American Bison in the world (~5,000 individuals).

  • Badlands National Park (South Dakota) – Offers excellent viewing in open prairie habitats.

  • Wind Cave National Park (South Dakota) – One of the first parks to restore bison populations.

  • Grand Teton National Park (Wyoming) – Bison often seen grazing along the Snake River valley.

  • Theodore Roosevelt National Park (North Dakota) – Known for scenic views and easy bison viewing.

🇨🇦 Canada

  • Elk Island National Park (Alberta) – Home to both wood bison and plains bison, with strong conservation focus.

  • Wood Buffalo National Park (Alberta/Northwest Territories) – The largest national park in Canada, home to the world’s largest wild wood bison population.

For the best sightings, visit in spring or fall, when bison are more active and visible, and explore open meadows, river valleys, and grasslands during morning or late afternoon hours.