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

IUCN Statuses

• Red List
  • Near Threatened (2016 assessment) (Aune et al. 2017)
    • Stable population trends
• Green List
  • Critically Depleted (2022 assessment) (Rogers et al. 2022)

CITES Status

• 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

• 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)

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.

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