A bison's appearance is led by its massive head that is crowned by a dark brown curly 'hairpiece' between two upwardly curving horns. The bison's foreparts are covered with this dark, woolly mane and beard, that is longer on the plains than the wood subspecies. The horns of a wood bison are longer and straighter than the plains bison. Behind the low-slung head that is supported by its heavily muscled neck, the bison's broad back rounds into a hump. The bison has short legs with large hoofs and its hindquarters are covered with a shorter, lighter-colored hair.
Young calves are a reddish brown color through their first summer.
A tail hanging loosely behind indicates that the animal is relaxed. If the tail is partially raised, the bison is alert. If the tail is horizontal, the bison is excited. After weaning from their mothers milk, young bison feed on a variety of green plants for the rest of their lives. Bison feed mostly on grass.