Skip to Main Content
It looks like you're using Internet Explorer 11 or older. This website works best with modern browsers such as the latest versions of Chrome, Firefox, Safari, and Edge. If you continue with this browser, you may see unexpected results.
San Diego Zoo Wildlife Alliance logo
San Diego Zoo Wildlife Alliance Library logo

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

History

  • 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

IUCN

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

CITES

  • 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)

SDZWA Library Links