This bull bison takes a short break from his daily forage to pose for a portrait. Bison are able to withstand sub-zero temperatures for weeks at a time, and they use their massive shoulder hump as a tool, enabling them to use their heads to move snow away from their winter forage. Bull bison can weigh up to a ton and can travel to speeds of 35 mph. Their estimated population of 55 million animals, which lasted until the mid-1800ís, was less than 300 by the turn of the century. This wholesale slaughter by European settlers opened the west to homestead, and also meant the end of a way of life for the cultures of the Native Americans of the plains.