Monkeys

Monkey Facts

Classification:

• Kingdom: Animalia
• Phylum: Chordata
• Subphylum: Vertebrata
• Class: Mammalia
• Order: Primate
• Suborder: Haplorhini
• Infraorder: Simiiformes
• Parvorder: Platyrrhini (New World Monkeys, includes five families: Callitrichidae, Cebidae, Aotidae, Pitheciidae, and Atelidae) and Catarrhini (includes two superfamilies: Cercopithecoidea or Old World monkeys and Hominoidea or apes)
• Families: Cercopithecidae (Old World monkeys, two subfamilies: Cercopithecinae, with thirteen genera, and Colobinae, with ten genera); Cebidae (New World monkeys: capuchins and squirrel monkeys, three genera); Callitrichidae (New World monkeys: marmosets and tamarins, seven genera); Aotidae (New World monkey: night monkeys, one genus); Pitheciidae (New World monkeys: titis, saki monkeys, and uakaris; four genera); and Atelidae (New World monkeys: howler, spider, woolly, and wooly spider monkeys; five genera)
• Geographical location: Africa and Asia (Catarrhines), Central and South America (Platyrrhines)
• Habitat: Mostly forests, some grasslands
• Gestational period: Old World monkeys, 5 to 6 months; New World monkeys, 4 to 7.5 months
• Life span: Old World monkeys, twenty to thirty-one years; New World monkeys, twelve to twenty-five years
• Special anatomy: Opposable thumbs, forward-facing eyes for binocular vision, large brain case

The term “monkey” is used to denote any simian (infraorder Simiiformes) that is not an ape (gibbons and hominids). Thus, it includes both members of the New World monkeys (parvorder Platyrrhini) as well as the Old World monkeys (parvorder Catarrhini, superfamily Cercopithecoidea). Monkeys have little in common with each other except for the fact that most are quadrupedal, but this does not eliminate all other primates, which includes the suborders Strepsirrhini (lemurs, galagos, pottos, and lorises) and Haplorhini (New World monkeys, Old World monkeys, and apes). It is unclear where the name “monkey” originated, although a common interpretation is that it relates to the medieval term “moneke,” meaning manikin.

Old World (Catarrhine) Monkeys

The Old World monkeys are the largest and most diverse family of primates, ranging over most of Africa, Asia, and Indonesia. The name Catarrhine means “downward-nosed,” referring to the fact that the nostrils are close together and point forward and down. Catarrhine monkeys include macaques, mangabeys, baboons, mandrills, vervet monkeys, guenons, colobuses, proboscis monkeys, and langurs. There are two subfamilies: the leaf-eating, arboreal Colobinae (examples include the colobus and the langur), and the omnivorous, often ground-dwelling Cercopithecinae (including the baboons, mandrills, macaques, and guenons). The Colobinae have a rather complex stomach and digestive system, whereas the Cercopithecinae have a simple stomach combined with cheek pouches in which food can be stored.

The macaques are the greatest in number among the Old World species, as well as the most widespread. The most northerly is the Japanese macaque (Macaca fuscata), which can live in cold, snowy climates. Other macaques live in dry, almost desertlike conditions in the tropics.

Old World species are generally larger than New World species and there is considerable sexual dimorphism. Most have bare buttock pads, which may be brightly colored. Their tails are seldom fully prehensile and may be significantly reduced in size. Almost all are active during the day, with excellent vision, hearing, and sense of smell. They communicate almost entirely by sight and sound, displaying a wide range of calls. Many display a range of facial expressions, used for communication with their own species as well as with other species nearby. Most are fully arboreal, but baboons are ground feeders, and macaques live both on the ground and in the trees.

When more than one species of monkey dwells in the same locality, the various species generally occupy different vegetation levels in order to avoid competition. This behavior is known as arboreal stratification. Most authors recognize four layers of vegetation in the tropics: the ground layer, lower canopy, middle canopy, and upper canopy. For instance, in the African guenons, De Brazza’s monkey (Cercopithecus neglectus) lives at the ground level, the red-tailed monkey (Cercopithecus ascanius) sleeps in the middle canopy but spends the day on the ground, the blue monkey (Cercopithecus mitis) lives in the upper canopy but forages in the middle, and the Diana monkey (Cercopithecus diana) lives solely in the upper canopy.

New World (Platyrrhine) Monkeys

The New World monkeys are a highly successful and diversified group colonizing Central and South America. The term usually refers to the parvorder Platyrrhini, meaning “flat-nosed.” As compared with the Catarrhine monkeys, the nostrils of the Platyrrhines are broadly separated and usually point to the sides. Members of the Platyrrhines include capuchins, howler monkeys, sakis, woolly monkeys, squirrel monkeys, and uakaris.

New World monkeys have long, thin fingers on each hand, with flattened or curved nails. Although their thumbs are not opposable, as they are in the human, the big toe can be opposed against the other toes for gripping branches tightly. New World monkeys are excellent runners and jumpers, swinging and leaping through their densely wooded habitats. Their tails are fully prehensile; they can grasp objects at the tip and curl around a branch and support the full body weight of the animal. In almost all cases, the tail is at least as long as the head and body, and it acts as a balancing organ, often being held in a curled pattern.

None of the New World monkeys are ground dwellers, unlike the baboons and other Old World monkeys. None of them have cheek pouches, and sexual dimorphism is rarely seen. New World monkeys are gregarious and live in family-based groups with much vocal and visual communication. They have highly developed olfactory organs that may also be used for communication. Males of many species contain a glandular patch on the sternum (breastbone) which they rub against tree branches to act as scent markers. Marking by means of urine and feces is also common. For instance, night monkeys coat their hands and feet with urine so that they leave a tell-tale scent wherever they go.

Families are well developed in most species of monkeys, although females do most of the caring for their offspring. Mothers usually carry their young on their backs until they are ready to move through the canopy on their own. Group size seems to depend primarily on the productivity and abundance of the foods typically eaten by the species. Species that live in small groups tend to feed on small, scattered, or scarce resources such as insects, small vine fruit, or newly emerged leaves of bamboo. Species that form large groups use abundant or clumped resources, such as fruits on large fig trees. Small family groups are typically one to three animals, while large groups may involve seven to twenty members.

Principal Terms

arboreal: living completely or primarily in the trees

opposable: a thumb which can be turned so that its pad makes contact with the pad of each of the fingers (as in the human)

prehensile: capable of grasping

quadrupedal: walking on all four feet

sexual dimorphism: the occurrence of anatomic or physiologic differences that distinguish males from females of a particular species

Bibliography

Boitani, Luigi, and Stefania Bertoli. Simon and Schuster’s Guide to Mammals. Trans. Simon Pleasaunce. Ed. Sydney Anderson. New York: Simon, 1983. Print.

Garber, Paul A., et al., eds. South American Primates: Comparative Perspectives in the Study of Behavior, Ecology, and Conservation. New York: Springer, 2009. Print.

Kuskowski, Alex. Monkeys. Minneapolis: ABDO, 2015. Print.

Macdonald, David, ed. The Encyclopedia of Mammals. New York: Facts on File, 1984. Print.

Nowak, Ronald. Walker’s Mammals of the World. 2 vols. 6th ed. Baltimore: Johns Hopkins UP, 1999. Print.

Voelker, William. The Natural History of Living Mammals. Medford: Plexus, 1986. Print.