Four bison move along a river after a fall snowstorm, this signals the approach of winter, where bison will move to their wintering grounds. Winter can be a hardship for most animals, but bison seem to have adapted well to the severe winters of the plains and rocky mountains. Bison are able to withstand sub-zero temperatures for weeks at a time. They use their massive shoulder hump as a tool, enabling them to use their heads to move snow away from their forage. Bull bison can weigh up to a ton and can travel to speeds of 45 m.p.h.