The African buffalo is not an ancestor of domestic cattle, and is only distantly related to other larger bovines. Owing to its unpredictable nature, which makes it highly dangerous to humans, the African buffalo has never been domesticated unlike its Asian counterpart, the water buffalo. Other than humans, African Cape buffaloes have few predators aside from lions and are capable of defending themselves. Being a member of the "big five" game family, the Cape buffalo is a sought-after trophy in hunting.
The African buffalo is a very robust species. Its shoulder height can range from 1 to 1.7 m (3.3 to 5.6 ft) and its head-and-body length can range from 1.7 to 3.4 m (5.6 to 11.2 ft). Compared with other large bovids, it has a long but stocky body (the body length can exceed the wild water buffalo, which is heavier and taller) and short but thickset legs, resulting in a relatively short standing height. The tail can range from 70 to 110 cm (28 to 43 in) long. Savannah-type buffaloes weigh 500 to 900 kg (1,100 to 2,000 lb), with males normally larger than females, reaching the upper weight range. In comparison, forest-type buffaloes, at 250 to 450 kg (600 to 1,000 lb), are only half that size. Its head is carried low; its top is located below the backline. The front hooves of the buffalo are wider than the rear, which is associated with the need to support the weight of the front part of the body, which is heavier and more powerful than the back.
Savannah-type buffaloes have black or dark brown coats with age. Old bulls have whitish circles around their eyes. Females tend to have more-reddish coats. Forest-type buffaloes are reddish brown in colour with horns that curve back and slightly up. Calves of both types have red coats.
A characteristic feature of the horns of adult male African buffalo is fusion of their bases, forming a continuous bone shield referred to as a "boss". From the base, the horns diverge downwards, then smoothly curve upwards and outwards. In large bulls, the distance between the ends of the horns can reach upwards of one metre. The horns form fully when the animal reaches the age of five or six years. In cows, the horns are, on average, 10–20% smaller, and the boss is less prominent. Forest buffalo horns are smaller than those of the savannah buffalo, usually measuring less than 40 centimetres (16 in), and are almost never fused.
Herd size is highly variable. The core of the herds is made up of related females, and their offspring, in an almost linear dominance hierarchy. The basic herds are surrounded by subherds of subordinate males, high-ranking males and females and old or invalid animals. The young males keep their distance from the dominant bull, who is recognizable by the thickness of his horns. During the dry season, males will split from the herd and form bachelor groups. Two types of bachelor herds occur: ones made of males aged four to seven years and those of males 12 years or older. During the wet season, the younger bulls rejoin a herd to mate with the females. They stay with them throughout the season to protect the calves. Some older bulls cease to rejoin the herd, as they can no longer compete with the younger, more aggressive males. Males have a linear dominance hierarchy based on age and size. Since a buffalo is safer when a herd is larger, dominant bulls may rely on subordinate bulls and sometimes tolerate their copulation.
Adult bulls will spar in play, dominance interactions or actual fights. A bull will approach another, lowing, with his horns down and wait for the other bull to do the same thing. When sparring, the bulls twist their horns from side to side. If the sparring is for play, the bull may rub its opponent's face and body during the sparring session. Actual fights are violent but rare and brief. Calves may also spar in play, but adult females rarely spar at all.
African buffaloes are notable for their apparent altruism. Females appear to exhibit some sort of "voting behavior". During resting time, the females will stand up, shuffle around, and sit back down again. They will sit in the direction they think they should move. After an hour of more shuffling, the females will travel in the direction they decide. This decision is communal and not based on hierarchy or dominance. When chased by predators, a herd will stick close together and make it hard for the predators to pick off one member. Calves are gathered in the middle. A buffalo herd will respond to the distress call of a captured member and try to rescue it. A calf's distress call will get the attention of not only the mother, but also the herd. Buffaloes will engage in mobbing behavior when fighting off predators. They have been recorded killing a lion and chasing lions up a tree and keeping them there for two hours, after the lions have killed a member of their group. Lion cubs can get trampled and killed. In one videotaped instance, known as the Battle at Kruger, a calf survived an attack by both lions and a crocodile after intervention of the herd.
African buffaloes make various vocalizations. Many calls are lower-pitched versions of those emitted by domestic cattle. They emit low-pitched, two- to four-second calls intermittently at three- to six-second intervals to signal the herd to move. To signal to the herd to change direction, leaders will emit "gritty", "creaking gate" sounds. When moving to drinking places, some individuals make long maaa calls up to 20 times a minute. When being aggressive, they make explosive grunts that may last long or turn into rumbling growl. Cows produce croaking calls when looking for their calves. Calves will make a similar call of a higher pitch when in distress. When threatened by predators, they make drawn-out waaaa calls. Dominant individuals make calls to announce their presence and location. A more intense version of the same call is emitted as a warning to an encroaching inferior. When grazing, they will make various sounds, such as brief bellows, grunts, honks and croaks.Other than one of the big five, it is known as "The Black Death" or "widowmaker", and is widely regarded as a very dangerous animal, as it gores and kills over 200 people every year. Buffaloes are sometimes reported to kill more people in Africa than any other animal, although the same claim is also made of hippos and crocodiles. Buffaloes are notorious among big game hunters as very dangerous animals, with wounded animals reported to ambush and attack pursuers.