Modern baboons (Superfamily Cercopithecoidea, Family Cercopithecinae, Tribe Papionini, and Genus Papio) are relatively large Old World monkeys of sub-Saharan Africa. There are five species of Papio (Hamadryas, Guinea, olive, yellow, and chacma baboons) spread across sub-Saharan Africa (see below for species names and their geographic distribution). It should be noted, however, that the five species are not completely isolated geographically and hybridization does occur. Guinea, olive, yellow, and chacma baboons are generally referred to as the savannah baboons.The hamadryas baboons live in the arid scrublands of Ethiopia. Mandrills (Mandrillus or Papio sphinx), drills (Mandrillus or Papio leucopaeus), mangabeys (Lopho-cebus and Cercocebus), geladas (Theropithecus), and the macaques {Macaco) are closely related to the baboons.
The baboons are extremely sexually dimorphic; males weigh above 16 kg, and the females are about half the size of the male. Males, especially the hamadryas baboon males, have long hair around their shoulders, giving the appearance of having a cape. Males but not females have large canines adapted for shearing the flesh of their opponents, whether conspecifics or predators. Large unicusp first premolars (the P3), known as sectorial premolars, have a ridge of heavy enamel that runs down the Prohylobates. These two genera preceded the separation of the two extant subfamilies of Old World monkeys, the Colobinae or leaf eaters, and the Cercopithecinae or fruit and insect eaters. During the Miocene, cercopithecine fossils are scarce compared to the more numerous fossil hominoids. The sparse fossil record of the genus Papio dates to about 3 to 4 million years ago and is limited to Africa.
One group of baboons, the kinda baboons (Papio cynocephlus kindae), a subgroup of yellow baboons (Papio cynocephlus), are particularly interesting. They are smaller and have a shorter face than the other savannah baboons. Instead of the dark coat color of other newborn baboons, kinda baboon neonates are born white, and the adult coat color is slightly more golden than other baboons. It might be tempting to view the kinda baboons as the ancestral form of the Papionini, but more fossils are needed to confirm or reject this hypothesis.
The social system of the savannah baboon is a multimale/multifemale troop in which the females remain in their natal troop throughout their lives,and the males emigrate at puberty. The troop forages and sleeps as a single unit, although troops have been observed to permanently divide into smaller troops. Males and females each have a dominance hierarchy; however, males are dominant to females by virtue of their large size. Mating is promiscuous, but females tend to mate with their male friends. Male/female friendships are important to the stability of a troop in that they provide for mutual support and aid, especially during agonistic encounters. Making friends with a female, moreover, can facilitate the entrance of a male into a new troop.
It has been difficult to determine the nature of the dominance hierarchy in baboon males. Some troops, especially small troops, may have a linear hierarch, but in other, perhaps larger troops, the males attain and maintain their high rank by forming coalitions. Rank among the females, however, is relatively stable and based on the rank of their mothers. Females also have stable friendships with other females that provide each other aid and support. Both rank and friendship help to maintain the stability of the baboon troop.
The hamadryas baboon, on the other hand, lives in uni-male bands in which the males actively herd his females away from other males. There are usually one to four females and their offspring in the uni-male bands. Mating occurs within the context of the uni-male group. The uni-male bands usually forage together as a group and independently of other uni-male groups. On their sleeping cliffs, however, the uni-male bands congregate into larger groups. The uni-male band is initially formed when a young male kidnaps an older juvenile female and begins to care for her. The young female stays with the male, and a new uni-male group is formed.
The reproductive life of baboons begins between 4 and 6 years of age, when males and females become sexually mature. However, males do not reach their full adult size until they are 9 to 10 years of age. The first sign of sexual maturity in a female baboon is the swelling of the area under the tail, known as the sex swelling, which correlates with ovulation and is attractive to male baboons. Baboon females generally have their first offspring by about the age of 7 years, and gestation lasts about 6 months. Assuming that an infant survives, the interbirth interval is a little over 2 years. The menstrual cycle covers about 35 to 40 days; the sex swelling appears about midcycle and lasts 7 to 10 days. Baboons in the wild may live to be 30 to 35 years of age. Incest is avoided by male emigration.
Baboon communication, similar to communication of other primates, is accomplished through body postures and facial gestures, vocalizations, grooming and other forms of touching behaviors, and odors referred to as pheromones. While fighting does occur, most aggression is mediated by body postures and facial gestures. In general, communication concerns the warning of the presence of predators; establishing and maintaining mother/infant and other friendly relationships; keeping contact during foraging; mediating acts of aggression, submission, and reconciliation; and broadcasting reproductive status.
Safety from predators and access to adequate food, water, other resources, and safe sleeping sites are important environmental variables influencing the daily foraging, resting, and sleeping cycle. Savannah baboons generally find refuge from predators and safe-sleeping sites in trees. Hamadryas baboons are known for their use of cliffs for sleeping, although all baboons will use trees or cliffs depending on what environmental features are available. Baboons have also been observed entering caves, presumably to escape temperature extremes and predators. The diet of baboons is best characterized as omnivorous and consists of young leaves, fruit, grasses and grass roots, and invertebrates. Baboons also eat vertebrates, including small mammals. Consuming mammals is unusual among primates. In areas where baboon habitat has been turned into agricultural lands, crop raiding is common.
References:
- Altmann, J. (1980). Baboon mothers and infants. Cambridge, MA: Harvard University Press.
- Altmann, S., & Altmann, J. (1970). Baboon ecology: African field research. Chicago: University Chicago Press.
- Fleagle, J. G. (1999). Primate adaptation and evolution (2nd ed.). New York: Academic Press.
- Groves, C. (2001). Primate taxonomy. Washington, DC: Smithsonian Institution Press.
- Kummer, H. (1968). Social organization of hamadryas baboons. Chicago: University of Chicago Press.
- Smuts, B. B. (1985). Sex and friendship in baboons.New York: Aldine.
