Bison is North America's largest mammal. The male bison reaches maturity between the ages of 6 and 9 years and it's maximum weight ranges from 800 to 1,200 kilos. The bison cow reaches maturity between the ages of 5 and 6 years and it's adult weight will be 500 to 700 kilos. The bison has a large head and black horns curved up and inward as well as a typical beard. Its wide shoulders carry withers that can reach 1.85 metres and their thorax is supported by 14 pairs of ribs. The bison's characteristic hump at the withers is formed by a crest of thoracic vertebrae. It's hindquarters are much more tapered than the front. Their croup leads to a tail that ends in a tuft of hair and they have black hooves.