Human impact

See also: Bison hunting

Photo from the 1870s of a pile of American bison skulls waiting to be ground for fertilizer.

Humans were almost exclusively accountable for the near-extinction of the American bison in the 1800s. At the beginning of the century, tens of millions of bison roamed North America. Humans slaughtered an estimated 50 million bison,^[47] not for sustenance, but for sport, supported by the military as an act of war on behalf of the U.S. Federal Government to restrict the dominant American Indian food supply.^[48] The overhunting of the bison reduced their population to hundreds. Attempts to revive the American bison have been highly successful. Farming of bison has increased their population to nearly 150,000. The American bison is, therefore, no longer considered an endangered species.^[49] The extinction of four species of bison (B. antiquus, B. latifrons, B. occidentalis, and B. priscus) was due to natural selection (see section Evolution and genetic history).
As of July 2015, an estimated 4,900 bison lived in Yellowstone National Park, the largest U.S. bison population on public land.^[50] During 1983–1985 visitors experienced 33 bison-related injuries (range = 10–13/year), so the park implemented education campaigns. After years of success, five injuries associated with bison encounters occurred in 2015, because visitors did not maintain the required distance of 75 ft (23 m) from bison while hiking or taking pictures.^[51]