American Bison – Bison bison

American Bison –  Bison bison
American bison  - Bison bison

American Bison

Kingdom – Animalia
Phylum – Chordata
Subphylum – Vertebrata
Class – Mammalia
Order – Artiodactyla
Family – Bovidae
Subfamily – Bovinae

Height – 5’- 6.5’

Length – Males: 10’ – 12.5’
Females: 6.5’ – 7.5’

Weight – Males: 1,600 – 2,000 pounds
Females: 900 – 1,100 pounds

Average lifespan in the wild – 20-25 years

Habitat – open spaces such as prairies, open forests, farmlands

Appearance – both sexes have horns, which are not shed.  Tails are long with tufts at the end.  The bulls have higher shoulder humps than the females, larger horns, a larger mass of heavy fur on the skull and shoulders, and a beard.

Behavior – Throughout most of the year, the bulls remain separate from the cows.  The females maintain hierarchical female groups, with one dominant individual. During the rut – which lasts from mid-summer to early fall – mature bulls court individual cows that are in heat.  The bulls engage in violent sparring battles for access to females, often smashing into each other head-on.

Bison spend the majority of their time grazing, and ruminate while resting.  They can often be seen coating themselves with dirt by rolling in a shallow depression in the ground, called a wallow.  Some possible explanations for this wallowing behavior include grooming to assist in shedding and the removal of lice and ticks, rutting behavior in the males, play behavior, thermoregulation, and relief from the itch of insect bites.

Bison are not territorial, generally clumping together in loose groups.  Prior to their population decimation, herds of bison would migrate long distances between their winter and summer grounds.  The current population is no longer migratory.

Diet – Bison are herbivorous; their diet consists of plants and lichens.

Characteristics – Bison have an excellent sense of hearing and smell.  They are capable of running at speeds up to 37 miles per hour.

Distribution – Bison are no longer free-ranging in Minnesota; they can now be found in established parks and reserves.

Similar species – There are no similar species in Minnesota.

Gestation – 9-10 months; the female usually bears only one calf

Tooth formula – 0/3, 0/1, 3/3, 3/3 x 2 = 32

Conservation – Bison once roamed the open areas of North America in groups numbering in the thousands, with a total population estimated between 50-70 million.  The species was nearly extirpated in the 1800’s due to widespread and unregulated hunting by the European settlers.  Although conservation efforts have yielded positive results, most American bison are captive.  Wild herds survive in only two locations – Yellowstone National Park, and Wood Buffalo National Park in Canada.

References:

Fashingbauer, B. A. 1965. The bison in Minnesota. Pp. 167-173 in J. B. Moyle, ed. Big
game in Minnesota. Minn. Dept. Cons. Tech. Bull. 9

Guthrie, R. D. 1966. Pelage of fossil bison – a new osteological index. Journal of
Mammalogy 47:725-727.

Haugan, A. O. 1974. Reproduction in the plains bison. Iowa State J. Res. 49:1-8.

Hazard, E. B. 1982. The mammals of Minnesota. University of Minnesota Press,
Minneapolis, Minnesota.

Jackson, H. H. 1961. Mammals of Wisconsin. University of Wisconsin Press, Madison,
Wisconsin.

Lott, D. F. 1974. Sexual and aggressive behaviour of American bison Bison bison. IUCN
Publ. 24(1):382-394.

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