Bison are strong survivors and have few predators except for humans, who reduced their population to the point at which, around 1900, there were fewer than a thousand plains bison left. In winter the vegetation on which these animals feed may be hidden beneath a deep blanket of snow however, this does not present a problem, for the bison use their hooves and massive heads to clear away the snow and then feed on the grasses below. When blizzards rage across the North American prairie, bison lower their heads and face directly into the storm.
The plains bison once ranged from Pennsylvania and Georgia to the Rockies, north to the edge of the Canadian forest, and south onto the central plateau of Mexico.
In North America there are two forms of bison, the plains bison and the woodland bison.
