Species Guide: American Bison (Bison bison)
Family: Bovidae
The American Bison is one of the most iconic large mammals indigenous to North America. Often colloquially referred to as the buffalo, this species has an evolutionary history shaped by grassland ecosystems and a cultural legacy deeply ingrained in many human societies. Prior to extensive hunting in the 19th century, tens of millions of bison roamed across the central regions of the continent. Today, their populations are primarily restricted to protected areas, reflecting both the recovery efforts and ongoing ecological challenges.
Appearance
Adult bulls are the largest members of the species. They exhibit a massive and muscular build with a broad head, a pronounced hump at the shoulders, and heavy forequarters. Their dark brown fur grows especially long and dense around the head, neck, and shoulders. Both sexes have short, curved horns, but males typically have slightly longer and thicker horns. Bulls can weigh more than 900 kilograms (1980 pounds) and achieve heights of about 1.8 meters at the shoulder.
Cows are smaller than bulls, with adults reaching roughly half the body mass of large males and standing nearer 1.5 meters at the shoulder. Their fur color and pattern closely resemble those of males, though their horns are generally finer and shorter.
Newborn bison calves are typically reddish-tan in color, which gradually changes toward the darker brown of adults over the first few months of life. Calves have proportionally smaller bodies and shorter horns. They grow rapidly, becoming more robust as they age.
Diet
American bison are specialized herbivores adapted to grazing. Their diet consists primarily of grasses and sedges typical of prairie and grassland habitats. They may also consume flowering plants, lichens, and, on occasion, low shrubs when grass availability changes with the seasons. Bison obtain much of their required moisture from the vegetation they eat and occasionally drink from open water sources. In winter, they use their powerful heads and shoulders to sweep snow aside to access forage beneath.
Habitat
Historically, bison occupied a range that extended from central Canada through the Great Plains of the United States and into northern Mexico. These animals thrived in grasslands, prairies, river valleys, and open savannas where abundant forage was available. Modern wild populations are now limited to reserves, national parks, and managed conservation herds in parts of the United States and Canada.
Behavior
Social Organization and Movement
Bison are social animals that form herds. Outside the breeding season, females and their young typically gather in maternal groups, while bulls may live singly or in small bachelor groups. Larger aggregations form during the mating season when males join female groups to compete for mating opportunities. Grazing occurs frequently throughout the day, often in loose groups that travel together across the landscape.
Communication
Bison communicate through a range of vocalizations, including low grunts and snorts mainly between mothers and calves, and deeper roars or bellows from males during mating season. These sounds can convey social cues about location, stress, or breeding readiness.
Life Cycle
Bison reach reproductive maturity at different ages: cows typically at two to three years, and bulls often not successfully breeding until they are six years old or more due to competition. The mating period occurs during midsummer, with a gestation lasting approximately nine and a half months. Calving usually takes place in the spring, and calves are nursed for up to eight months and generally weaned by the end of their first year.
Biometrics
| Length | Up to 3.8 m |
| Height at Shoulder | 1.5-1.8 m |
| Body Weight | 900-1000 Kg |
| Longevity | 12-20 Years |
Natural Predators
Adult bison have few natural predators due to their size and strength. However, calves and weaker individuals can fall prey to large carnivores such as wolves and grizzly bears. Predation risk is highest for young animals, especially in the first year of life. In historical contexts, humans were also significant predators of bison, particularly during periods of commercial hunting in the 1800s.
Relationship to Humans
Bison have held deep cultural and ecological significance for many human societies, especially Indigenous peoples of the Great Plains. They provided essential resources, including meat, hides for clothing, shelter, sinew for tools, and a central role in cultural practices.
European settlement and westward expansion in North America brought dramatic changes. During the 19th century, commercial hunting and organized slaughter drove bison populations to the brink of extermination. From tens of millions, numbers dropped precipitously by the late 1800s. Modern conservation efforts have helped populations recover in protected areas and private herds, though wild populations remain much reduced compared to historical levels.
Human cultural narratives include numerous oral traditions and allegories featuring bison, reflecting their importance in systems of meaning for many Indigenous communities.
Conservation Status
The American bison is currently classified as near threatened by conservation assessments, with a generally stable population trend in managed and protected herds. Although numbers have rebounded from historic lows, the wide range and genetic purity of many bison remain limited due to past overhunting and widespread crossbreeding with domestic cattle. Efforts by conservation organizations, federal agencies, and tribal nations continue to focus on restoring larger, ecologically functional herds and expanded habitat connectivity.
Global
Conservation Status
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References
- O’Brien, D. (2017) Plains Bison. Lincoln, Nebraska ; University of Nebraska Press [Accessed 29/12/2025]
Citations
- By William T. Hornaday – Hornaday, William T. 1889. “Extermination of the North American Bison With a Sketch of Its Discovery and Life History.” In Report of the National Museum Under the Direction of the Smithsonian Institution 1887, pp. 367-548. Washington: Government Printing Office.Cornell University: Persuasive Cartography: The PJ Mode Collection, Public Domain, [Accessed 29/12/2025] ↩︎
