American bison

Physical Description and Distinguishing Subspecies

The American bison possesses a distinctive physique characterized by a massive head, a pronounced shoulder hump, and slimmer hindquarters. Its coat changes seasonally, featuring a long, shaggy, dark brown winter coat and a lighter, shorter summer coat. Sexual dimorphism is pronounced, with males being significantly larger and heavier than females. The species is generally divided into two subspecies, the plains bison and the wood bison. The plains bison is smaller with a more rounded hump, while the wood bison is larger with a taller, square hump and is considered one of the largest wild bovids globally. Head-rump lengths can reach 3.5 metres for males, with tails adding 30 to 95 centimetres. Both sexes have short, curved horns that can grow up to 60 centimetres long, which are used in intra herd disputes and defense. For the first two months, calves exhibit a lighter reddish orange colour, earning them the nickname red dogs.

Evolutionary Journey and Genetic Relationships

Bison first appeared in Asia during the Early Pleistocene approximately 2.6 million years ago. They arrived in North America much later, between 195,000 and 135,000 years ago, descending from the Siberian steppe bison that migrated across the Bering land bridge. Their first appearance defines the Rancholabrean faunal stage due to their major ecological impact. In North America, they rapidly diversified into species like the enormous long horned Bison latifrons. The modern American bison is believed to have evolved from Bison antiquus at the end of the Pleistocene. Genetic evidence from nuclear DNA indicates their closest living relatives are yaks, and they are nested within the genus Bos. Mitochondrial DNA reveals a complex relationship with European bison, which are more closely related to domestic cattle, suggesting ancient introgression or incomplete lineage sorting. This genetic history is distinct from the more recent but limited cattle gene introgression that occurred during the 19th century population bottleneck.

Historic Dominion and the Path to Near Extinction

The historical range of the American bison, known as the great bison belt, was a vast tract of grassland spanning from central Alaska to the Gulf of Mexico and from nearly the Atlantic Seaboard to the Rocky Mountains. Herds shaped the continent's first thoroughfares, creating trails through seasonal migrations between feeding grounds and salt licks. These trails were later used by Indigenous peoples, explorers, and pioneers, and some became routes for railways. The species was a fundamental resource for Plains Indigenous nations, providing food, hides for clothing and shelter, and bones and horns for tools. The combination of commercial hunting for hides, systematic slaughter to undermine Indigenous nations as part of a genocidal campaign, and the introduction of bovine diseases from domestic cattle caused a catastrophic decline. From an estimated 60 million in the late 18th century, the population was reduced to a mere 541 animals by 1889, representing one of the most severe mammalian population collapses in history.

The Modern Recovery and Population Structure

Recovery began with a handful of ranchers and conservationists gathering remnant animals in the late 19th and early 20th centuries. Conservation efforts expanded significantly by the mid 20th century. The most recent 2026 estimate from the IUCN SSC Bison Specialist Group places the total North American population between 430,000 and 530,000 individuals. Of these, only about 31,000 are considered wild, free range bison not primarily confined by fencing. The majority of bison are in approximately 6,400 commercial herds, while roughly 20,500 are part of 62 conservation herds. Reintroduction programs have successfully re established wild herds in multiple regions. In 2014, US Tribes and Canadian First Nations signed a landmark treaty to collaborate on restoration, the first such agreement in nearly 150 years. Herds now roam in national parks from Wood Buffalo and Banff in Canada to Yellowstone in the United States, and reserves in northern Mexico like Janos Biosphere Reserve.

Habitat Use and Migratory Behaviour

American bison are animals of open and semiopen grasslands, prairies, river valleys, and scrublands like sagebrush. They also historically used some lightly wooded areas. Contrary to being solely plains dwellers, some herds routinely use mountainous terrain. The Yellowstone herd is frequently found above 2,400 metres elevation, and the reintroduced Banff herd roams high ridges and steep drainages. In Yukon, bison often summer in alpine plateaus above the treeline. Bison are migratory grazers, and their daily movements are influenced by seasonal vegetation, rutting activity, and insect harassment. They have been recorded traveling an average of 3 kilometres per day in summer ranges. Their diet is predominantly grasses and sedges, but they will turn to browsing sagebrush and other plants in times of scarcity. On mixed prairie, cool season grasses can compose 79 to 96 percent of their diet.

Social Hierarchy and Reproductive Biology

Bison society is organized around maternal herds of females and their young, and bachelor herds or solitary males. Male offspring leave their maternal herd around age three. The herds mix during the breeding season from July through September. Dominant bulls maintain small harems, a behaviour known as tending, where they follow females and shield them from rival males. Challenging bulls bellow or roar to get a female's attention, and the tending bull must respond in kind. Dominance hierarchies exist for both sexes and are influenced by birth date, with earlier born calves tending to be larger and more dominant as adults. Gestation lasts approximately 285 days, resulting in a single calf. Cows nurse their calves for at least 7 to 8 months, and if not pregnant again, a calf may nurse for 18 months. Cows reach sexual maturity at three years. Bison have a life expectancy around 15 years in the wild, but in protected herds with predation, individuals have been known to live into their early to mid twenties.

Cultural and Official Recognition

The American bison is deeply embedded in the life and culture of the Indigenous peoples of the Great Plains. In many Plains Indian languages, distinct words exist for male and female bison, reflecting their special significance, a linguistic distinction not always present for other large mammals. In wider recognition of its ecological and historical importance, the bison was designated the national mammal of the United States on May 9, 2016. This status grants it official recognition alongside the bald eagle. The year 2026 marks the tenth anniversary of this designation, an occasion noted by museums and conservation groups. The animal's representation continues to be prominent, with suggestions for its use as a mascot for major events like the 2026 FIFA World Cup, highlighting its enduring status as a unique North American symbol.

Ongoing Conservation and Reintroduction Projects

Contemporary conservation focuses on maintaining genetic integrity, expanding habitat, and managing disease. Many conservation herds use DNA testing to identify and manage the low level cattle genetics present from historic crossbreeding. Active reintroduction projects continue to restore bison to their historic landscape. In Canada, plains bison were reintroduced to Banff National Park where they exhibit natural migratory behaviour. In Mexico, genetically pure bison were reintroduced to the Janos Biosphere Reserve in 2009, with a second herd formed in Maderas del Carmen in 2020. A unique Pleistocene rewilding project has seen wood bison from Alberta's Elk Island National Park introduced to Yakutia, Russia, since 2006. These bison, the most similar living relative to the extinct steppe bison, have adapted well to the cold and were officially registered on Yakutia's Red List in 2019. Such projects underscore the bison's role as a keystone species capable of shaping diverse ecosystems.

Comparative Differences with European Bison

Although similar in appearance, the American bison and the European bison exhibit notable differences in physicality and behaviour. The American bison is slightly heavier on average due to a less rangy build and has shorter legs, making it slightly shorter at the shoulder. Its neck is set differently, leading it to graze more and browse less than its European cousin. The nose of the European bison is set farther forward relative to the forehead. The American bison's body is hairier, but its tail has less hair than that of the European species. Their fighting styles differ significantly European bison horns point forward, facilitating interlocking fights like domestic cattle, while American bison prefer charging. Furthermore, American bison are more easily tamed and have historically bred more readily with domestic cattle, a factor that contributed to genetic management challenges during their recovery.

Questions about American bison

What is the difference between a bison and a buffalo?

In North American English, bison and buffalo refer to the same animal, the American bison. The term buffalo originated with early European explorers like Samuel de Champlain, who used the French word buffles after learning of the animal from Indigenous nations. Scientifically, it is a bison, distinct from true buffalo species like the Asian water buffalo and African buffalo. The word bison entered English from French in the early 17th century. In precise biological and international contexts, using bison avoids confusion with the bovids of Africa and Asia.

How many American bison are left today?

The most recent authoritative estimate from 2026, provided by the IUCN SSC Bison Specialist Group, states the total North American population is between 430,000 and 530,000 animals. This total includes all bison in commercial, conservation, and tribal herds. Of this number, only approximately 31,000 are considered wild, free range bison not primarily confined by fencing. The remaining animals are in roughly 6,400 commercial herds and 62 conservation herds. This represents a monumental recovery from the 1889 low of 541 individuals.

Where can I see wild bison in Canada?

Canada hosts several key wild bison populations. Wood Buffalo National Park protects the world's largest free roaming wood bison herd. Elk Island National Park in Alberta maintains important conservation herds of both pure wood and plains bison, and serves as a source herd for reintroductions worldwide. Plains bison have been successfully reintroduced to Banff National Park where they roam mountainous terrain. Other populations exist in Grasslands National Park, Saskatchewan, and in various provincial parks and wildlife management areas in Alberta, Saskatchewan, Manitoba, British Columbia, and Yukon, where they often use alpine habitats in summer.

Why did bison almost go extinct?

The near extinction resulted from a deliberate and concerted campaign in the 19th century. Commercial hunting for hides and meat was extensive. More systematically, the United States government and settlers engaged in widespread slaughter to destroy a primary resource for Plains Indigenous nations, directly supporting a genocidal policy to force them onto reservations by eliminating their traditional way of life. This was combined with the introduction of bovine diseases such as brucellosis from domestic cattle, which further decimated the herds. These factors collectively reduced the population from tens of millions to just over five hundred in less than a century.

How big can an American bison get?

The American bison is the heaviest land animal in North America. Mature bulls are vastly larger than cows. The heaviest wild bull ever recorded weighed 1,270 kilograms. They can stand up to 186 centimetres at the shoulder for plains bison and 201 centimetres for wood bison. Captive, farm raised bison have been recorded at even higher weights, with one reaching 1,724 kilograms.

What is the status of the American bison as a national symbol?

The American bison was officially named the national mammal of the United States on May 9, 2016. This legislative act recognized the animal's central role in the nation's history, ecology, and culture. The bison now holds an official status alongside the bald eagle. The year 2026 marks the tenth anniversary of this designation, which has been commemorated by institutions like the Smithsonian. The designation underscores the bison's story of resilience and recovery, and its image remains a powerful representation of North America's natural heritage and the ongoing efforts to restore wild places and species.

Sources: Wikipedia and current public reporting, checked by the Your Space Hamilton desk. Last updated 2026-10-19.