The Vervet Monkey (Chlorocebus pygerythrus), sometimes simply known as the Vervet, is an Old World monkey in the family Cercopithecidae. (The common term “vervet” is also sometimes used to refer to all the members of the genus Chlorocebus.)
Vervet monkeys live in multi-female, multi-male groups (Turner, Maiers, & Mott, 1986) varying in size from 5 individuals to 76 (Fedigan & Fedigan, 1988). The average group size is 24 monkeys (Struthsaker, 1967). The sex ratio in a vervet monkey group is one female to one male (Struthsaker, 1963). Male vervet monkeys move to neighboring groups when they reach sexual maturity around the age of 5 (Cheney & Seyfarth, 1983). When the males do leave their kin group, they move directly to a new one in the surrounding area, in which, the males receive much aggression from the females of that group (Pusey & Packer, 1987). Female vervet monkeys remain in their natal group. (Cheney & Seyfarth, 1983). For male vervet monkeys, there is a clear alpha and no clear ranking among subordinates. The females have a linear hierarchical system in which the order of the birth and kin relationships play an important part in the structure of the hierarchy (McGuire, 1982). Female offspring assume the social status of their mothers (McGuire, 1982). There is a possibility for rank change for females when an older matriarch dies, and the females of other matrilines challenge the remaining daughters. In vervet colonies, grandmothers have a stabilizing effect on social relationships for females; young adult females who have their birth mothers still living in the group usually receive less aggression from the nonkin females (Fairbanks, 1988). Allomothering is a common social characteristic in the vervet colonies (Strusaker, 1971). As part of the intragroup dynamics, vervets participate in dyadic encounters that sometimes involve more than two monkeys (Struthsaker, unpublished findings). The coalitions they form are not always random, indicating there are social preferences in these encounters; low ranked vervets are only solicitors, while middle ranks are solicitors and solicitees, and high rank vervets are solicitees (Struthsaker, 1967). It is true that vervet monkeys have the ability to classify other individuals across the groups that surround them and within their own group (Cheney & Seyfarth, 1982). Vervet monkeys have great cognitive skills when dealing with each other but less sophisticated skills when interacting with objects in their environment (Cheney & Seyfarth, 1985).