The Prehistoric Bison of Yellowstone National Park

On the Ground • When Yellowstone National Park (YNP) was established in 1872, American bison (Bison bison) were living in the park's forests and mountains. • A study conducted in the 1960s concluded that those were Mountain bison (Bison bison athabascae), a subspecies adapted to mountain habitat. It was assumed that those historical bison occupied their native habitat and had done so in prehistoric times. • When archaeological evidence of YNP bison was discovered in the mid-1990s it seemed reasonable to assume that those bones were derived from a herd of native prehistoric bison. • However, a review of archaeological, historical, genetic, and ecological evidence suggests a different history. Namely, herds of bison were absent before 1840. Sometime between 1840 and the mid-1850s, plains bison were driven into the mountain forest in and near YNP. In those forests, bison were relatively safe from horse-mounted, bow-and-arrow-armed Native American hunters. • Archaeological evidence suggests that YNP’s prehistoric bison were bulls that left herds on the low-elevation plains that surround the park; the bulls would have traveled up mountain drainages to the Yellowstone volcanic plateau. • Bison played no significant role in the ecological processes that shaped YNP’s prehistoric landscape. YNP’s modern bison herd is causing significant changes in range condition.