Where the buffalo roam: The role of history and genetics in the conservation of bison on U.S. federal lands

As an emblem of the Great Plains, American Indians, and wildlife conservation, the American bison (Bison bison) is one of the most visible and well-known of wildlife species in North America (fig. 1, above). Species of the genus Bison originally entered the continent via the Bering land bridge from northern Eurasia in the Illinoian glacial period of the Pleistocene epoch (125,000–500,000 years ago). Bison are the largest species in North America to have survived the late Pleistocene–early Holocene megafauna extinction period (around 9,000–11,000 years ago), but likely experienced a dramatic population reduction triggered by environmental changes and increased human hunting pressures around this time (Dary 1989; McDonald 1981). The modern American bison species (Bison bison) emerged and expanded across the grasslands of North America around 4,000–5,000 years ago (McDonald 1981). As the major grazer of the continent, bison populations ranged from central Mexico to northern Canada and nearly from the east to west coasts (fig. 2; McDonald 1981), with 25–40 million bison estimated to have roamed the Great Plains prior to the 19th century (Flores 1991; McHugh 1972; Shaw 1995).