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Wood Bison (Bison bison athabascae)
Species Profile

Did You Know?

Wood bison are the largest native land mammal in North America.

Special Status Listing: Yes, see Status, Trends and Threats.

General Description

Wood bison are one of two subspecies of modern American bison. They have a dense coat of warm and durable hair that is dark brown in the winter and lighter in the spring. They begin to lose their winter coat as temperatures warm in the early spring. By mid-summer it is completely shed and has been replaced with new hair. They have curving horns that point upward and hair on their chin that resembles a beard. Their head and shoulders are large compared to their hindquarters. The wood bison’s backbone slopes almost straight up above the shoulders to form a pronounced hump. From there it slopes downward to the hips. Adult males are approximately 6 feet tall at the shoulder, 10 feet long, and weigh over 2,000 pounds. The females are smaller, generally weighing around 1,200 pounds.

Similar Species

Plains bison (B. bison bison) are the other subspecies of American bison. They have a similar appearance, but wood bison are larger and have a taller hump. The tallest part of the hump is also further forward than in plains bison, and the “beard” of wood bison is more pointed than that of plains bison.

Life History

Reproduction and Growth

Female wood bison are sexually mature around 2 years old and can have their first calf when they are 3. They generally have a single calf twice every three years. Wood bison are pregnant for 9 months and give birth from April to August with most calves born in May. Newborn calves are red in color, similar to moose calves. In order to evade predators, calves can stand within 30 minutes of birth and can run and kick within hours. After a week, calves will begin grazing but continue to nurse for several months. After 10 weeks, their coats begin to darken and become dark brown by about 15 weeks of age.

Feeding Ecology

Wood bison are primarily grazers and mainly eat grasses, sedges, and forbs. They can use a variety of other plants; for example, silverberry and willow leaves make up part of their summer diet. Wood bison graze in meadows, around lakes and rivers, and in recent burns.


Wood bison live in groups of up 20 to 60 animals during most of the year, but adult bulls usually live in smaller groups and stay separate from the larger groups of cows and young bison except during the breeding season in late summer. They have strong social bonds and like to be near other bison.


Bison generally remain within a home range but move between seasonal ranges, and move each day from meadow to meadow, where they graze and rest before moving on. Although bison move slowly when feeding, they are capable of moving rapidly over long distances. The size of their year round range tends to increase with population size, and also depends on habitat quality. In lower quality habitats they will move over a larger home range.

Range and Habitat

Wood bison once ranged across northwestern Canada and were also found in a large region in Interior and Southcentral Alaska. At present, free-ranging wood bison are found only in Canada, but there is a captive herd of about 135 animals being held at the Alaska Wildlife Conservation Center near Portage, Alaska, as part of Alaska’s wood bison restoration effort.

Status, Trends, and Threats


There are currently about 4,700 wood bison in six, healthy, free-ranging herds in Canada. There is a similar number in herds infected with cattle diseases in the Wood Buffalo National Park (WBNP) area in Canada. There are also domestic herds of wood bison in Canada. The wood bison is listed as endangered under the Endangered Species Act (ESA). To learn more, visit the ADF&G Special Status page for wood bison. To learn more, visit the ADF&G Special Status page for wood bison.

NatureServe: Global – G4T2Q (Imperiled)
ESA: Threatened


Wood bison were the last bison to occur naturally in Alaska but disappeared during the last few hundred years because of unregulated hunting and changes in habitat distribution. By 1900 there were fewer than 300 individuals remaining in Canada. Through conservation and management efforts in Canada, the population of 300 has grown to over 4,000 disease-free animals, with a total of about 10,000 animals in the wild. The State of Alaska has developed a wood bison restoration program with the goal of reintroducing wood bison in parts of their original range in Alaska. Three areas with high quality habitat have been identified in interior Alaska, and together could support at least 3,000 bison.


The main factors that constrain additional wood bison recovery in Canada are cattle diseases (bovine tuberculosis and brucellosis) and habitat loss. Bovine tuberculosis, brucellosis, and anthrax are the diseases of concern for wood bison herds, although there are six herds that are not infected. The presence of diseased herds in the WBNP area reduces the habitat available to disease-free herds. Wolf predation can affect the growth of some herds, especially those infected with disease, but has had little effect in reducing populations in Canada, which are stable or increasing. Agriculture and urban development have claimed some of the original range of the species, but there is a large amount of unoccupied habitat available in Alaska and some additional range in Canada.

Fast Facts

  • Size
    Males — 2,000 lbs; females — 1,200 lbs.
  • Lifespan
    20 years
  • Distribution
    Canada with one captive herd in Alaska
  • Diet
    Grasses, sedges, forbs, silverberry, willow
  • Predators
  • Reproduction
    1 calf 2 out of every 3 years