At the Caldwell Zoo in Tyler, Texas we stop and take a look at a Buffalo (Bison) that has a persistant itch. Bison are the largest mammal in North America. Bison used to be plentiful in North America, but, with the expansion of early settlers, the animal was hunted almost to extinction. Native Americans relied on the bison for many things such as food, shelter and tools. Most people think bison are a slow and clumsy animal. However, bison have the agility of a deer and can outrun most horses. They are a rugged animal that can survive in a multitude of harsh climates.