The vervet monkeys or green monkeys are medium-sized primates from the family of Old World monkeys. There are six species currently recognized, although some classify them all as a single species with numerous subspecies. Either way, they make up the entirety of the genus Chlorocebus.
These monkeys are found only in sub-Saharan Africa; their range extends from Senegal and Ethiopia down to South Africa. A small population, which were taken as pets by slavers and were transported with the enslaved Africans, are found in the Caribbean, on the islands of Barbados, Saint Kitts, Nevis, and Saint Maarten. A colony also exists in Broward County, Florida.
Unlike the closely related guenons, vervets are not primarily forest dwellers, rather, they are semi-arboreal and semi-terrestrial, spending most of the day on the ground feeding and then sleeping at night in the trees. However they must drink each day and are dependent on water, so they are never far from rivers or lakes. Like most other members of the Cercopithecoidea superfamily, they have cheek pouches for storing food. They are diurnal, and are particularly active in the early morning and in the later afternoon or early evening.
Green monkeys live in large groups, which can consist of some males, many females and their offspring, and can be as large as 80 animals. The group hierarchy plays an important role: dominant males and females are given priority in the search for food, and are groomed by subordinate members of the group. While young males must leave their group once they are fully mature, females remain and take on the role of their mothers. These monkeys are territorial animals, and a group can occupy an area of approximately 0.1 to 1 km². They use a wide variety of vocalizations. They can with warn off members of other groups from their territory, and they can also warn members of their own troop of dangers from predators, using different calls for different predators. Monkeys scream when they are disciplined by members of the troop. Facial expressions and body posturing serve as additional communication tools. Their social interactions are highly complex. Where alliances can be formed for benefit, deception is sometimes used. Physical affection is important between family members.
Vervet monkeys are omnivores. The majority of their diet, however, is grasses and fruits. Occasionally they also eat small vertebrates and insects. On the island of Saint Kitts, vervet monkeys will commonly steal brightly coloured alcoholic drinks left behind by tourists on the beach. Many tourists have also found out these monkeys will deliver a powerful bite if they are cornered or threatened. Care should be taken when approaching any vervet monkeys, although these monkeys will retreat from a confrontational situation if given an escape route. If at one point they were domesticated in centuries gone past, they are no longer. In Africa, the documented attacks by these monkeys are extremely rare as compared with dog attacks, in spite of living very closely with humans and often being threatened by humans and their dogs.
In order to signal mating readiness, the female presents her vulva to the male. Since groups are made of several more females than males, each male mates with several females. Males do not take part in raising the young, but other females of the group (the "aunties") take part in sharing the burden. The dominance hierarchy also comes into play here, as the offspring of the more dominant group members get preferential treatment. The gestation time is about 160 days, and births are typically of a single young. The births usually happen at the beginning of the rainy season, when there is sufficient food available. The young are weaned at about 6 months of age and are fully mature in 4 to 5 years. The life expectancy of the green monkeys is 25 years in captivity, and about 10-12 years in the wild.
In Africa, many monkeys are killed by powerlines, dogs, vehicles, shooting, poisoning, and hunting both as food and for traditional medicines. Added to this, there is an increase in desertification, and loss of habitat due to agriculture and urbanisation. As a result population numbers in troops are declining in urban areas to an average of between 15 and 25 individuals, with many troops disappearing altogether.