The American bison or American buffalo (Bos bison), the largest mammal in North America, once roamed the continent in vast herds and helped to shape the ecology of the Great Plains, as well as the history of the United States of America. Formidable in stature, the American bison’s massive frame is accentuated by its towering shoulder hump. Resting low on a short, stocky neck, the bulky head features a broad forehead, short, up-curving horns and a straggly beard. The head, neck, shoulders, and forelegs are covered in a long, shaggy, brownish-black coat, while the hair on the remainder of the body is considerably shorter and lighter in colour. Female bisons are on average shorter than the males, and have a smaller hump, a thinner neck and more slender horns.