While temperatures continue to drop as we approach winter, the American bison couldn't care less. These burly mammals get ready for snow with their shaggy coats and massive bodies that can weigh up to 900 kilograms. Despite their size, they are agile and can run up to 64 kilometres per hour. The bison population plummeted due to overhunting and westward expansion. At its lowest point, only a few hundred bison were left in the wild. Bison herds have resided in Yellowstone National Park since prehistoric times, a site that is no stranger to frigid temperatures.