Diet

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Bison are herbivores and eat simple foods.They generally rest during day and graze in the mornings and the evenings. The bison's main foodstuff is grass and sedges,^[39] though they will also eat any available low-lying shrubbery.^{[citation needed]} In the winter, bison forage for grass under the snow. If little grass is available, they will eat the twigs of shrubs. Bison are notably better browsers than cattle, since cattle are more obligate grazers, though wood bison have also been described as "obligate grazers".^[40] Wisent tend to browse on shrubs and low-hanging trees more often than do the American bison, which prefer grass to shrubbery and trees.^[41]

Predators

Wolves hunting bison

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Due to their size, bison have few predators. Five notable exceptions are the grey wolf, human, brown bear, coyote, and grizzly bear.^[42] The grey wolf generally takes down a bison while in a pack, but cases of a single wolf killing bison have been reported.^[35] Brown bear also prey on bison calves, often by driving off the pack and consuming the wolves' kill.^[4] Historically and prehistorically, lions, tigers, Smilodon, and cave hyenas had posed threats to bison.