Baboons are African and Arabian Old World monkeys belonging to the genus Papio, part of the subfamily Cercopithecinae. There are five species, which are some of the largest non-hominid members of the primate order; only the mandrill and the drill are larger. Previously, the closely related gelada (genus Theropithecus) and the two species (mandrill and drill) of genus Mandrillus were grouped in the same genus, and these Old World monkeys are still often referred to as baboons in everyday speech. They are P. ursinus (chacma baboon, found in southern Africa), P. papio (western, red, or Guinea baboon, found in the far western Africa), P. hamadryas (hamadryas baboon, found in the Horn of Africa and south-western Arabia), P. anubis (olive baboon, found in the north-central African savanna) and P. cynocephalus (yellow baboon, found in south-central and eastern Africa). Many authors distinguish P. hamadryas as a full species, but regard all the others as subspecies of P. cynocephalus and refer to them collectively as "savanna baboons". This may not be helpful: it is based on the argument that the hamadryas baboon is behaviorally and physically distinct from other baboon species, and that this reflects a separate evolutionary history.
Their diet is omnivorous, but mostly vegetarian; yet they eat insects and occasionally prey on fish, shellfish, hares, birds, vervet monkeys, and small antelopes. They are foragers and are active at irregular times throughout the day and night. They can raid human dwellings and in South Africa they have been known to prey on sheep and goats.
Their principal predators are humans, the lion, both the spotted and striped hyena and the leopard. They are however considered a difficult prey for the leopard, which is mostly a threat to young baboons. Large males will often confront them by flashing their eyelids, showing their teeth by yawning, making gestures, and chasing after the intruder/predator.
The structure within the troop varies considerably between hamadryas baboons and the remaining species, sometimes collectively referred to as savanna baboons. The hamadryas baboon often appear in very large groups composed of many smaller harems (one male with four or so females) to which females from elsewhere in the troop are recruited while they're still too young to breed. Other baboon species have a more promiscuous structure with a strict dominance hierarchy based on the matriline. The hamadryas baboon group will typically include a younger male, but he will not attempt to mate with the females unless the older male is removed.
Baboons can determine from vocal exchanges what the dominance relations are between individuals.
Baboon mating behavior varies greatly depending on the social structure of the troop. In the mixed groups of savanna baboons, each male can mate with any female. The mating order among the males depends partially on their social ranking, and fights between males are not unusual. To garner this friendship, they may help groom the female, help care for her young, or supply them with food. The probability is high that those young are their offspring. Some females clearly prefer such friendly males as mates. However, males will also take infants during fights in order to protect themselves from harm.
A female initiates mating by presenting her swollen rump to the male. But "presenting" can also be used as a submissive gesture and is observed in males as well. This submissive gesture has many unspoken meanings amongst the troop.