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American Bison (Bison bison) Fact Sheet: Population & Conservation Status

American Bison (Bison bison)

Population Status

Population estimates
(Aune et al. 2017)

  • Species-level
    • Total population
      • 31,000 individuals in 68 conservation herds
    • Mature individuals
      • 11,000-13,000 individuals
  • Subspecies-level
    • Plains bison
      • 20,000 individuals
    • Wood bison
      • 11,000 individuals


  • Prior to 1800's: estimated 50 million B. bison bison in North America (Nowak 1999)
  • Late 1800's: bison in North America were nearly extinct.
  • 1889: 835 bison living in the United States (Grzimek 1990)
  • 1891: Wood Bison (Bison bison athabascae) offered legal protection by Canadians
  • 1905: American Bison Society founded at New York city's Bronx Zoo; Theodore Roosevelt was honorary president,
  • 1920's: Wood Bison (B. b. athabascae)numbered around 1,500
  • 1920's: 6000 Plains bison introduced to Wood Buffalo National Park in Canada, transmitting bovine tuberculosis to Wood Bison
  • 1957: A small wild population of B. b. athabascae discovered in Canada's Wood Buffalo Park (Nowak 1990)
  • 1979: Wood bison classified as endangered
  • 1988: Wood bison downlisted to threatened
  • 2008: About 150 free-ranging bison live at the 125,000 acre Camp Pendleton in southern California. These animals descend from 14 individuals donated in 1973 by the San Diego Zoo.

Conservation Status


  • Near Threatened (2016 assessment) (Aune et al. 2017)
    • Stable population trends.


  • Not listed (UNEP 2019)
    • Wood bison, B. b. athabascae, subspecies listed in Appendix II in 1997; deleted in 2017

Endangered Species Act

  • Bison bison bison: not listed
  • Bison bison athabascae: Threatenened
    • Listed 1970

Threats to Survival

  • Habitat loss
  • Hunting in 1800 and 1900's nearly exterminated bison in North America. (McDonald 1981)
    • Their gene pool experienced a bottleneck but genetic diversity hasn't declined significantly.
  • Some researchers argue that bison will increasingly be eradicated by genetic modification as they are domesticated. (Lott 2002)
    • Over 90 percent of bison in North America are "undergoing domestication'" (Lott 2002)
    • Cattle genes found in nearly more than half of public herds in the U.S. and Canada and in all but one of 50 sampled private herds. (Halbert & Derr 2007)

Herds That Once Roamed

Pile of American Bison skulls

Buffalo skulls to be used for fertilizer and charcoal. Michigan Carbon Works, USA, circa 1870.

Image credit: Unknown artist. Burton Historical Collection at the Detroit Public Library; made available thru Wikimedia Commons. Public domain.

Note: This is a retouched historical image.

Page Citations

Grizmek (1990)
Halbert & Derr (2007)
Lott (2002)
Marris (2009)
McDonald (1981)
Nowak (1999)

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