The North America and European bison are the largest terrestrial mammals in America and Europe. Bison are nomadic grazers and travel in herds, except for the non-dominant bulls, which travel alone or in small groups during most of the year. The American and European bison are the largest terrestrial mammals in North America and Europe. Bison are nomadic grazers and travel in herds, except for the non-dominant bulls, which travel alone or in small groups during most of the year. American bison are known for living in the Great Plains. Both species were hunted close to extinction during the 19th and 20th centuries but have since rebounded, although the European bison is still endangered. Unlike the Asian water buffalo, bison have never been domesticated, although the American bison is kept on some farms.
Bison are born without their trademark hump and horns and live for approximately twenty years. They grow to maturity at two to three years, although males continue to grow until about thier seventh year. Adult bulls express a high degree of dominance competitiveness during mating season. Male bison fight for females and these fights often result in injury or death. After the bison mate, the herd splits up into smaller herds. Calves are born nine months after mating. The mothers take care of and nurse their young for a year. Bison grow to as much as to 11.5 feet (3.5m) long, and 6.5 feet (2m) tall at the shoulder and weigh up to one ton (1,000 Kg).
Wallowing is a common behavior of bison. A bison wallow is a shallow depression in the soil, either wet or dry. Bison roll in these depressions, covering themselves with mud or dust. Possible explanations suggested for wallowing behavior include grooming behavior associated with moulting, male-male interaction (typically rutting behavior), social behavior for group cohesion, play behavior, relief from skin irritation due to biting insects, reduction of ectoparasite load (ticks and lice), and thermoregulation. In the process of walloving bison may become infected by the fatal disease anthrax, which may occur naturally in the soil. Bison have a fairly simple diet. The bison's main food is grass. Bison also eat the low lying shrubbery that is available. In the winter, bison forage in the snow looking for grass. If there is little grass available, bison have to resort to eating the twigs of the shrubs and plants.