Heavy snow doesn’t usually bother bison, though truly extreme storms can pose a danger. Their thick fur is so insulating that snow often piles up on their backs without melting. In winter, they grow a dense, woolly undercoat beneath longer guard hairs. This natural layering, along with thickened skin and fat beneath the hide, traps body heat and blocks out most of the cold.

American bison have been seen standing through blizzards covered in snow that stays frozen, showing how little heat escapes. When they move, they can often shake off the snow like powder. They can handle subzero temperatures on open range.