Bisons inhabiting Yellowstone National Park have to face extreme winter conditions. Intense snowfall covers the grass with a thick layer, making it challenging for bisons to access their food. Additionally, the area experiences exceptionally low temperatures, sometimes dropping below -40 degrees Celsius (and Fahrenheit). In these harsh conditions, thick fur plays a crucial role, protecting against the cold, and sturdy hooves enable the bisons to dig out dried grass from beneath the snow. The ultimate line of defense is also a substantial layer of fat, helping them survive prolonged periods without access to food during Yellowstone's severe winters.