A bull is a male cow. They are more muscular than the females, with thicker bones, larger feet, a very muscular neck, and a large, bony head with protective ridges over the eyes. These all help bulls fight one another to win dominance over a herd of cows for reproduction. Bulles are commonly thought to be angered by the color red, but this is not true. Bulls are red-green colorblind, and it is the movement of a matador's cape that provokes a reaction from a bull.