American Bison

American Bison
(Bison (possibly to be changed to Bos) bison)

Once numbering 90 million, the American bison now only survives in refuges and parks. The symbol of the American Great Plains these ‘buffalo’ form single-sex herds of 20-60 animals.

American Bison – Subspecies

Possibly 2 subspecies: B.b. bison (plains bison) and B.b. athabascae (wood bison), although genetic data suggests that these populations are not distinct and that coat differences are simply due to environmental influences.

American BisonAmerican Bison – Statistics

380cm long, with a 90cm tail and standing up to 195cm at the shoulder. Males weigh around 818kg, females 545kg.

American Bison – Physical Description

A large and heavily built member of the cattle family, with strongly built front quarters and a noticeable shoulder hump. The coat is dark and shaggy, particularly over the head and front quarters of the males, and in the summer the long hair of the hind quarters can be shed to leave a short coat. The head is large and heavy, and bears two short, upwardly curving horns and a beard. The tail has a dark tassle.

American Bison – Distribution

Originally from Alaska south to northern Mexico in North America, but now only survives in protected areas over some of this range. The European bison, which may be the same species, once roamed over the same latitudes in Eurasia.

American Bison – Habitat

Once found throughout forests and plains, but now survives only in refuges which are mostly on prairies.

American Bison – DietAmerican Bison

Mainly grasses, but other vegetation when necessary.

American Bison – Behavior

Bison live in herds of 20-60, separated by sex. Cow herds are made up of females and young males under the age of three, whilst bulls are solitary or form herds. Both sexes have strict hierarchies. Grazing takes place in bursts throughout the day, and the herds travel in search of new pastures, often travelling in single file, led by the dominant member.

American Bison – Reproduction

As the breeding season approaches, from late June to September, the dominant males associate with the cow herds and search for fertile females. The males ‘rut’ by rolling in mud soaked with their own urine, posturing, and taking part in head-to-head fights. Gestation lasts around 285 days, with the calves being born around mid-April to May. The female leaves her herd to give birth in a protected area with lots of undergrowth. Young calves are initially a reddish colour, and become darker in the first few months of life. They are nursed for 7-8 months, and weaned at one year. Sexual maturity is reached after 2-3 years, although bulls will not be able to win the right to mate until they are at least 6 years old.

American Bison – Conservation status

Listed as ‘Lower Risk – Conservation Dependent’, although the wood bison (if it is a true subspecies) is Endangered.

American Bison – Notes

Before Europeans arrived in North America the bison population is estimated to have been 90 million. By 1890 it was only 1,000. They were culled for their meat, hides, and also to destroy the Native Americans’ food supply. Their numbers have recovered, but they only survive in small protected refuges.