(Cercopithecinae)
Class: Mammalia
Order: Primates
Family: Cercopithecidae
Subfamily: Cercopithecinae
Thumbnail description
Medium-sized mammals with forward-facing, quite large eyes, relatively large brains and a quadrupedal pattern of locomotion involving grasping hands and feet
Size
2 lb 12 oz (1.25 kg) to 48 lb (21.7 kg)
Number of genera, species
11 genera; 72 species
Habitat
Wide range of habitats, ranging from semi-arid scrub with only sparse vegetation to dense evergreen tropical rainforest
Conservation status
Critically Endangered: 1 species; Endangered: 8 species; Vulnerable: 10 species; Near Threatened: 16 species; Data Deficient: 3 species
Distribution
Predominantly occur in Africa south of the Sahara; macaques occur outside Africa, having a wide distribution throughout Asia and Southeast Asia
Evolution and systematics
The higher primates (suborder Anthropoidea) are divided into the broad-nosed monkeys of the New World (infraorder Platyrrhini) and the narrow-nosed monkeys and apes of the Old World (infraorder Catarrhini). The Old World monkeys and apes, which occur in Africa, Asia and Southeast Asia, are uniformly characterized by a dental formula of (I2/2 C1/1 P2/2 M3/3) × 2 = 32, differing from all New World monkeys by reduction in the number of premolars from three to two in each tooth row. All Old World monkeys and apes have trichromatic color vision comparable to that of humans. As a group, the Old World monkeys are distinguished from the apes by the presence in both upper and lower jaws of four-cusped molars with the cusps linked in pairs to form transverse cutting ridges (bilophodonty). Furthermore, all Old World monkeys possess well-developed hardened sitting pads (ischial callosities) on the buttocks, supported by broad, roughened bony flanges (ischial tuberosities) on the pelvis. Among the apes, only the gibbons show a similar development. The Old World monkeys are divided into two main groups, the cheek-pouched monkeys (subfamily Cercopithecinae) and the leaf-monkeys (subfamily Colobinae). Defining features of these two groups are related to their feeding habits. Whereas all cercopithecine monkeys possess cheek pouches for the temporary storage of food, leaf-monkeys have a complex, multi-chambered stomach as an adaptation for digestion of plant cell walls in their leaf-rich diet with the aid of symbiotic bacteria. There is also a consistent and immediately obvious difference in skull morphology, in that the distance between the eye sockets (interorbital distance) is small in cheek-pouched monkeys and large in leaf-monkeys.
Two tribes can be recognized among the cercopithecine monkeys: the Cercopithecini (guenons) and the Papionini (baboons, geladas, mangabeys, drill, mandrill, and macaques). The guenons are generally smaller and more arboreal than the baboons and their relatives, which tend to be large-bodied and at least partially terrestrial; but there is some degree of overlap in these features. For instance, the patas monkey (Erythrocebus patas) is a member of the guenon tribe but is quite large-bodied and predominantly terrestrial.
Old World monkeys commonly show some degree of sexual dimorphism, in which males and females differ in features other than those directly related to reproduction. Males and females of a species can differ markedly in fur coloration, in overall body size and in the size of the canine teeth, although these features can vary to some extent independently. The most striking example of sexual dimorphism in all three aspects is provided by the mandrill (Mandrillus sphinx), in which males weigh more than twice as much as females, have strikingly large canine teeth and are more brightly colored.
Chromosomal and molecular evidence indicates that the two tribes Cercopithecini and Papioni are both monophyletic, each being derived from a separate common ancestor after the cheek-pouched monkeys diverged from the leaf-monkeys. Within the Cercopithecini, there appear to be two main clusters, one formed by most of the forest-living guenons (Cercopithecus species) and the other containing the talapoins (Miopithecus), the vervets or grivets (Chlorocebus), l'Hoest's guenon (Cercopithecus lhoesti), and the patas monkey (Erythrocebus patas). Within the Papionini, there is a basic division between the baboons, macaques, and geladas on one branch and the mandrills on another. Unexpectedly, the Old World monkeys known as mangabeys, which were all originally classified as species of the genus Cercocebus, turned out to belong to two distinct lineages. The genus name Cercocebus is now reserved for more terrestrial species related to the mandrill, whereas the genus name Lophocebus is used for more arboreal species related to baboons.
The early fossil history of the Old World monkeys is still poorly documented. Two early Miocene forms from Africa, from deposits dated at about 20 million years ago (mya) are
Prohylobates and Victoriapithecus, both of which have bilophodont (two-ridged) molar teeth. These early fossil forms were originally known only from isolated teeth and jaw fragments, and this is still the case for Prohylobates. However, a fairly complete skull and parts of the postcranial skeleton have been reported for Victoriapithecus, and as a result it is known that this genus was characterized by a short interorbital distance and by possession of ischial tuberosities on the pelvis. But it is unclear whether Victoriapithecus is specifically related to modern cheek-pouched monkeys, as the small interorbital distance suggests. It is not until the late Miocene and the Pliocene, less than 10 mya, that fossil remains of Old World monkeys become relatively well documented, and by that stage it is certainly possible to distinguish between cercopithecines (relatives of cheek-pouched monkeys) and colobines (relatives of leaf-monkeys). Cercopithecine monkeys are comparatively common in Pliocene deposits of Africa. Many of them resemble modern baboons (e.g. Dinopithecus, Dolichopithecus and Gorgopithecus), and there are also relatives of the modern gelada, some of them almost as big as a female gorilla, which are placed in the same genus Theropithecus. During warm interglacial periods of the middle Pleistocene, macaques related to the modern Barbary macaque (Macaca sylvanus) were present in central Europe, but they subsequently became restricted to North Africa.
Physical characteristics
Coloration of the body fur is often relatively inconspicuous and occasionally cryptic, generally being darker dorsally and paler ventrally. The face is usually virtually naked, although in some species there is a beard-like tuft of hair on the chin. However, in many cases the fur and skin on the face and sometimes on other areas of the body are conspicuously patterned, notably in various guenons, where species-specific coloration patterns on the head are commonly emphasized by characteristic head movements. Striking color contrasts are also frequently present in the genital region. In males, the scrotum and/or penis are often distinctively colored, while in females of some species there is often a conspicuous sex skin that changes in color and size over the course of the ovarian cycle. The most colorful species is undoubtedly the mandrill (Mandrillus sphinx). In this species, the faces of males have a bright red nose flanked by blue, ridged paranasal bulges along with white whiskers, and there is a large, orange-yellow beard, while the rump is also colored red and blue and the penis is bright red. Females are similarly, although less brightly, colored; but they also have prominent sexual swellings that are bright red at peak inflation.
In the head, the eyes are always directed directly forwards and the snout is mildly to strongly elongated. In common with other higher primates, a rhinarium (a naked, moist area of skin around the nostrils present in most mammals) is always completely lacking. The nostrils are relatively close-set and point downward. Cheek pouches are consistently present, but the degree of development varies from species to species. The dental formula, which is the same in all Old World monkeys and apes, is (I2/2 C1/1 P2/2 M3/3) × 2 = 32. The canine teeth are typically large, stabbing teeth, and the rear edges of the upper canines are honed against the leading edges of the anterior premolars in the lower jaw. The molars in both upper and lower jaws are bilophodont. Cercopithecine monkeys typically walk and run quadrupedally both in the trees and on the ground, and the arms and legs are of approximately equal length. In the trees, they are agile climbers. On the hand, the thumb is always well developed, and fine manipulative actions are particularly prevalent in terrestrial species. In all Old World monkeys, including leaf-monkeys (colobines), well-developed hardened sitting pads (ischial callosities) are present on the buttocks, and these are supported by broad, roughened bony flanges (ischial tuberosities) on the pelvis. The tail is very variable in length, being very long in some species and reduced to a small stump in others. As a rule, arboreal species tend to have a relatively long tail, whereas marked reduction of the tail is found in species that spend much of their time on the ground. Head and body length varies from 14 in (35 cm) to 30 in (75 cm), while tail length varies from practically zero to 34 in (86 cm), according to species. Body mass ranges from 2 lb 12 oz (1.25 kg) for the diminutive talapoin (Miopithecus talapoin) to 48 lb (31.6 kg) for a male mandrill (Mandrillus sphinx).
Distribution
Cheek-pouched monkeys of the subfamily Cercopithecinae are largely confined to Africa south of the Sahara, where they are very widely distributed. The only cercopithecine monkeys to occur outside Africa are the macaques (genus Macaca), which occur widely in Southeast Asia. Just one macaque species, the Barbary macaque (Macaca sylvanus) is found in Africa, occurring north of the Sahara in Algeria and Morocco.
Habitat
Cheek-pouched monkeys occur in a remarkably wide range of habitats, spanning the spectrum from semi-arid scrub vegetation marked by strictly seasonal rainfall to highly humid evergreen tropical rainforest with year-round rainfall. Most species depend upon trees to some extent, at least for sleeping sites during the night. Most species typically inhabit evergreen tropical rainforest. This applies to most guenons (genera Allenopithecus and Cercopithecus), talapoins (genus Miopithecus), mangabeys (genera Cercocebus and Lophocebus), drills and mandrills (genus Mandrillus) and many Asiatic macaque species (genus Macaca). By contrast, baboons (genus Papio), geladas (genus Theropithecus), a few guenons (genera Chlorocebus and Erythrocebus), and some macaque species (e.g. the Barbary macaque, Macaca sylvanus) commonly live in relatively open, dry-country habitats. The most extreme example of the latter is probably provided by the chacma baboon (Papio ursinus), which lives under extremely dry, almost desert-like conditions in some parts of southern Africa.
Behavior
All members of the subfamily Cercopithecinae are diurnal. Most species are essentially arboreal, but there are also numerous species that have become adapted for terrestrial activity. In all cases, locomotion is typically quadrupedal. All cheek-pouched monkeys live in gregarious social groups that move around and feed as relatively cohesive units, organized in some cases as harem groups with a single adult male (one-male groups) and in others as groups containing several adult males (multimale groups). Monogamy is extremely rare as a social system in cercopithecine monkeys. Forest-living guenons of the genus Cercopithecus, patas monkeys (Erythrocebus), hamadryas baboons (Papio hamadryas), and geladas (Theropithecus) all form one-male groups. In some species that exhibit one-male groups, surplus males form bachelor male groups, and it is possible for several harem groups and bachelor male groups to live in large herds, as is the case with hamadryas baboons and geladas. As a general rule, females tend to stay in their natal groups, whereas males migrate at round the time of sexual maturity.
Feeding ecology and diet
As a rule, cheek-pouched monkeys feed predominantly on relatively high-energy foods such as fruits, seeds, insects, and (occasionally) other vertebrates. Although many species also eat leaves, these typically represent a minor part of the diet and relatively nutritious young leaves are generally preferred. However, the bilophodont teeth that characterize all Old World monkeys probably represents an adaptation for mastication of resistant material such as leaves, so it seems likely that the common Old World ancestor of both cheek-pouched monkeys (subfamily Cercopithecinae) and leaf-monkeys (sub-family Colobinae) was folivorous at least to some extent. On the other hand, the cheek pouches that characterize all cercopithecine monkeys probably constitute an adaptation for temporary storage of small, easily collected food items such as fruits and seeds, so their development in the common ancestor of Cercopithecinae probably presumably a shift towards increased consumption of such food items. With respect to diet, the most aberrant species among the cheek-pouched monkeys is the gelada (Theropithecus gelada), which feeds extensively on grass shoots, seeds and roots and shuffles along on its hindquarters much of the day while foraging.
Reproductive biology
Monogamy is rare in cercopithecine monkeys; most are polygamous.
Single births are typical, although twins are born very occasionally, and two teats (mammae) are consistently present in the chest region. All species have a menstrual cycle lasting approximately a month and marked by externally visible menstrual bleeding. In many species, females have a conspicuous sex skin in the genital region that changes in coloration and size over the course of the ovarian cycle. Maximum swelling and the most prominent degree of coloration (commonly bright red) occur around the time of ovulation, approximately halfway between menstrual episodes. Conspicuous sex swellings are found in baboons, mandrills, some mangabeys, short-tailed macaques, swamp monkeys and talapoins, but they are less prominent or virtually absent in long-tailed macaques and forest-living guenons and other mangabeys. Geladas are highly unusual in that the sex skin is located on the chest, as a patch bordered by vesicles that varies in color and prominence over the ovarian cycle. This special development is undoubtedly linked to the fact that geladas spend much of the day shuffling along on their hindquarters while foraging. Placentation is of a highly invasive hemochorial type. The gestation period is long, varying between 162 days for the smallest species, the talapoin (Miopithecus talapoin), and 187 days for one of the largest, the chacma baboon (Papio ursinus).
Conservation status
One species is Critically Endangered (Macaca pagensis), eight species are Endangered (Cercopithecus diana, Cercopithecus erythrogaster, Cercopithecus preussi, Cercopithecus sclateri, Macaca maurus, Macaca nigra, Macaca silenus, and Mandrillus leucophaeus), 10 are Vulnerable (Cercopithecus erythrotis, Cercopithecus solatus, Macaca arctoides, Macaca assamensis, Macaca cyclopis, Macaca leonina, Macaca nemestrina, Macaca sinica, Macaca sylvanus, and Mandrillus sphinx), and 16 are Near Threatened (Allenopithecus nigroviridis, Cercocebus atys, Cercocebus galeritus, Cercocebus torquatus, Cercopithecus hamlyni, Cercopithecus lhoesti, Lophocebus aterrimus, Macaca fascicularis, Macaca hecki, Macaca mulatta, Macaca nigrescens, Macaca thibetana, Macaca tonkeana, Papio hamadryas, Papio papio, and Theropithecus gelada). Three species are listed as Data Deficient (Cercopithecus dryas, Macaca fuscata, and Macaca ochreata).
Significance to humans
Cheek-pouched monkeys are commonly hunted for food (bushmeat) in Africa, Asia and Southeast Asia, although they are often protected at least to some extent by local customs in Asia and parts of Southeast Asia, as is the case with rhesus macaques (Macaca mulatta) and bonnet macaques (Macaca radiata) in India. Monkeys of the subfamily Cercopithecinae have also been used extensively in biomedical research because they are relatively closely related to humans. The rhesus macaque has long been established as a standard laboratory species and, among other things, served as a basic model for the study of reproductive processes and maternal behavior. Other macaque species, various baboons and some guenon species have also been widely used in biomedical research.
Species accounts
Allen's swamp monkeyPatas monkey
Angolan talapoin
Grivet
Moustached guenon
Rhesus macaque
Barbary macaque
Gray-cheeked mangabey
Collared mangabey
Hamadryas baboon
Gelada
Mandrill
Resources
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[Article by: Robert D. Martin, PhD]
