American Bison

The American bison (Bison bison) is the largest land mammal in North America, with mature bulls weighing up to 2,000 pounds and standing six feet tall at the shoulder. Two subspecies are recognized: the plains bison (Bison bison bison), which ranges across the grasslands of the Great Plains, and the wood bison (Bison bison athabascae), found in boreal forests and meadows of northwestern Canada and Alaska. Listed as Near Threatened on the IUCN Red List, the species once numbered an estimated 30 to 60 million animals across the continent before commercial hunting and habitat loss reduced the wild population to fewer than 1,000 individuals by the late 19th century.

Bison are a keystone species on the Great Plains, shaping the landscape through grazing, wallowing, and soil disturbance in ways that directly support prairie plant diversity and provide habitat for species including the burrowing owl (Athene cunicularia) and black-footed ferret (Mustela nigripes). Today, the total population across conservation herds and private ranches numbers around 500,000, but the IUCN estimates that fewer than 20,000 are considered wild or semi-wild, and only a handful of herds maintain the genetic diversity needed for long-term viability. Ongoing threats include habitat fragmentation, hybridization with domestic cattle, disease transmission (particularly brucellosis), and political barriers to range expansion beyond designated federal lands.