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American Bison (Bison bison) Fact Sheet: Physical Characteristics

American Bison (Bison bison)

Physical Characteristics

Body measurements

Attribute Males Females
Weight 554-907 kg (1,221-2,000 lb) 318-545 kg (701-1,202 lb)
Body Length 3,040-3,800 mm (10-12 ft) 2,130-3180 mm (7.0-10.4 ft)
Tail Length 330-910 mm (1.1-3.0 ft) 300-510 mm (1.0-1.7 ft)

General Appearance

General Description

  • A large headed, massive, tall but narrow-bodied bovid with a pronounced shoulder hump, short and robust legs, brown hair with a black nose, lips, tongue, hooves and horns.

Teeth 

  • 32 teeth in total: 12 molars, 12 premolars, 2 canines, 6 incisors
  • Teeth high crowned (hypsodont) and cresent-cusped ("moon tooth" or selenodont)
  • All deciduous teeth present at birth
  • First permanent tooth erupts during first year

Horns

  • Arch backwards and upwards with points aimed somewhat inwards (Grzimek 1990)

Pelage 

  • In general, more luxuriant and longer than the European bison (Nowak 1999)
  • Brown; appears black from a distance
  • Head, underbelly, flanks, and rear are dark brown
  • Longest hairs on forelegs and beard
    • Males swing their "pantaloons" in threat displays (Lott 1974)
  • Thick mat of hair on the male's forehead helps protect from the head-clashing impacts (Guthrie 1990)
  • Winter coat is wooly under fur overlain by coarse guard hairs; this hair bleaches to tan
    • Molt begins in late winter/early spring
  • Heavier, denser, and finer pelage than in many cattle (Lott 2003)
    • Have ten times the number of cattle's primary hairs per square inch
    • Pelage enables these animals to withstand subzero, windy winters
  • Short eyelashes compared to cattle help keep their eye lids from accumulating ice
  • Young are much lighter colored than adults. (Guthrie 2003)
    • This difference follows a general rule for young of animals that live in large groups in open environments where the young need to be protected.
    • European bison (B. bonasus) living in smaller groups have young that are colored more like the adults.

Sexual Dimorphism

  • Males up to two-thirds larger than females with stouter, more robust and evenly curving horns, a much larger hump, longer pelage, and a thicker neck.
  • Considering fossil species of bison and the two species living in North America and Europe today, Bison bison bison has a moderate amount of sexual dimorphism, the European Bison bonasus a low amount, and the fossil Steppe Bison had extreme dimorphism, especially in the size of the skull. (Guthrie 1990)

Other Physical and Physiological Characteristics

  • Acute sense of smell
  • Good eyesight; can recognize objects the size of a horse with a rider at 1 km (.6 mi) and moving objects at 2 km (1.2 mi). (McHugh 1958)
  • Strong head-to-head impacts from dominance fighting between bulls are made less damaging to the brain by a system of bone struts which divide the inner and outer walls of the skull. (Guthrie 1990)

American Bison

Head of American Bison

Head of an American Bison.

Image taken at Wildlife Prairie State Park near Hanna City, Illinois in 2003.

© Ted Lee Eubanks, Jr./FERMATA Inc. http://www.fhwa.dot.gov/byways/photos/58693 [link broken]. Made available on Wikimedia Commons: copyrighted free use granted.

Page Citations

Buchholtz & Sambraus (1990)
Guthrie (1990)
Lott (1974, 2003)
Meagher (1986)
McDonald (1981)
McHugh (1958)
Nowak (1999)

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