hargreavesphoto.com

Figure 1. Bison in Wind Cave National Park, South Dakota.

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).

By the 1820s, bison in North America were already in a state of continuous decline, especially in the South and East (Flores 1991; Garretson 1938). Evidence on many fronts indicates the initial decline was due to both natural and anthropogenic (human-induced) forces (Flores 1991; Isenberg 2000). For example, the introduction of nonnative animal species led to increased hunting efficiency by aboriginal peoples with the proliferation of the horse culture, spread of exotic diseases (e.g., tuberculosis and brucellosis from cattle), and competition for grazing and water sources with growing populations of cattle, horses, and sheep. Natural pressures including fire, predation by wolves, and severe weather events such as droughts, floods, and blizzards also served to limit historical bison population sizes (Isenberg 2000). Uncontrolled hide hunting by both aboriginal and Euro-American hunters, facilitated by advances in firearms and transcontinental rail transportation, advanced the rapid decline leading to the well-documented, precipitous population crash of the late 1800s (Coder 1975; Garretson 1938). A preference for young female bison hides likely added to the population decline by disrupting herd social structure and natality (birth) rates. Fewer than 1,000 American bison—including both the plains and wood bison types—existed in the world by the late 1880s, and the species appeared to be at risk of extinction (Coder 1975; Soper 1941). The timely formation of six captive herds from 1873 to 1904 by private individuals and governmental protection of two remnant wild herds in the United States (Yellowstone National Park, established in 1872) and Canada (Wood Buffalo National Park, federally protected from 1893, park established in 1922) effectively served to save the species from extinction (table 1); locations indicated on fig. 2). The individuals involved in the early bison conservation movement were primarily cattle ranchers concerned with the disappearance of large, free-roaming bison herds. For example, the Texas cattle rancher Charles Goodnight (fig. 3), at the behest of his wife (Haley 1949), captured bison in the panhandle of Texas during the late 1870s and early 1880s to form a small captive herd. From these few herds, a combined total of fewer than 500 bison served as the foundation stock from which all bison in existence today are derived (Coder 1975; Soper 1941).

Fewer than 500 bison served as the foundation stock from which all bison in existence today are derived.