A bull is an intact adult male of the species Bos taurus. More muscular and aggressive than the female of the species, the cow, the bull has long been an important symbol in many cultures, and plays a significant role in beef ranching, dairy farming, and a variety of other cultural activities, including bull fighting and bull riding.

Bulls are much more muscular than cows, with thicker bones, larger feet, a very muscular neck, and a large, bony head with protective ridges over the eyes. These features assist bulls in fighting for domination over a herd, giving the winner superior access to cows for reproduction. The hair is generally shorter on the body, but the neck and head often have a “mane” of curlier, wooly hair. Bulls are usually about the same height as cows or a little taller, but because of the additional muscle and bone mass, they often weigh far more. Most of the time, a bull has a hump on his shoulders. In horned cattle, the horns of bulls tend to be thicker and somewhat shorter than those of cows, and in many breeds, they curve outwards in a flat arc rather than upwards in a lyre shape. It is not true, as is commonly believed, that bulls have horns and cows do not: the presence of horns depends on the breed, or in horned breeds on whether the horns have been disbudded. (It is true, however, that in many breeds of sheep only the males have horns.) Cattle that naturally do not have horns are referred to as polled, or muleys.

Castrated male cattle are physically similar to females in build and horn shape, although if allowed to reach maturity, they may be considerably taller than either bulls or cows, with heavily muscled shoulders and necks.

Adult bulls may weigh between 500 and 1,000 kg (1,100 and 2,200 lb). Most are capable of aggressive behavior and require careful handling to ensure safety of humans and other animals. Those of dairy breeds may be more prone to aggression, while beef breeds are somewhat less aggressive, though beef breeds such as the Spanish Fighting Bull and related animals are also noted for aggressive tendencies, which are further encouraged by selective breeding.

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