Forage Competition as a Possible Cause of Bison Extinction in Eurasia and of Native Horses in North America

Based on an analysis of both original and literature material on the nutrition of horses and bison, a possible cause of the “extinction” of steppe bison in Eurasia and of native horses in North America 10–12 thousand years ago is estimated. Horses and bison, both differing in the morphology and functioning of the digestive system, are similar in the composition of consumed plants and nutrition parameters, this causing forage competition when grazing together on common pastures. At the turn of the Pleistocene and Holocene in Eurasia, the change of dry and cold Pleistocene tundra steppe to snowy Holocene steppes with snow-covered food inaccessible to bison could have led to the disappearance of steppe bison forms () in Eurasia. Horses that successfully forage from under the snow by digging with their hooves survived into the Holocene period and inhabited the steppe and desert plains of Eurasia. In North America, the appearance of the steppe bison () at the end of the Pleistocene and the beginning of the Holocene (13–12 thousand years ago) could have led to competition with native horses. The well-known Holocene extinction of horses at the same time (about 12 thousand years ago) allows us to recognize competition with bison as a possible cause of the extinction of native horses in North America. Bison’s two forms, steppe and forest ones, survived into the Holocene epoch and actively spread across the North American continent.