Vervet monkey

Appearance

The vervet monkey has a black face with a white fringe of hair, while the overall hair color is mostly grizzled-grey. The species exhibits sexual dimorphism; the males are larger in weight and body length. Adult males weigh between 3.9 and 8.0 kg, averaging 5.5 kg, and have a body length between 420 and 600 mm, averaging 490 mm from the top of the head to the base of the tail. Adult females weigh between 3.4 and 5.3 kg and average 4.1 kg, and measure between 300 and 495 mm, averaging 426 mm.

Distribution

The vervet monkey ranges throughout much of Southern and East Africa, being found from Ethiopia, Somalia and extreme southern South Sudan, to South Africa. It is not found west of the East African Rift or the Luangwa River, where it is replaced by the closely related malbrouck. The vervet monkey inhabits savanna, riverine woodland, coastal forest and mountains up to 4000 m. They are adaptable and able to persist in secondary and/or highly fragmented vegetation, including cultivated areas, and sometimes are found living in both rural and urban environments. Annual home range size has been observed to be as high as 176 ha with an average population density of 54.68 animals/km².

Introduced vervet monkeys are naturalized in Ascension Island, Cape Verde, Bermuda, Barbados, Bahamas, Cuba, Jamaica, Haiti, Dominican Republic, and Saint Kitts and Nevis. Dania Beach, Florida is home to about 20 introduced vervets.

Behavior

When males reach sexual maturity, they move to a neighboring group. Often, males will move with a brother or peer, presumably for protection against aggression by males and females of the resident group. Groups that had previously transferred males show significantly less aggression upon the arrival of another male. In almost every case, males migrate to adjacent groups. This obviously increases benefits in regard to distance traveled, but also reduces the amount of genetic variance, increasing the likelihood of inbreeding.

Females remain in their groups throughout life. Separate dominance hierarchies are found for each sex. Male hierarchies are determined by age, tenure in the group, fighting abilities, and allies, while female hierarchies are dependent on maternal social status. A large proportion of interactions occur between individuals which are similarly ranked and closely related. Between unrelated individuals, there is female competition for grooming members of high-ranking families, presumably to gain more access to resources. These observations suggest individual recognition is possible and enables discrimination of genetic relatedness and social status. Interactions between different groups are variable, ranging from highly aggressive to friendly. Furthermore, individuals seem to be able to recognize cross-group vocalizations, and identify from and to which monkey each call is intended, even if the call is made by a subadult male which is likely to transfer groups. This suggests the members within a group are actively monitoring the activity of other groups, including the movement of individuals within a group.

Within groups, aggression is directed primarily at individuals that are lower on the hierarchy. Once an individual is three years or older, it is considerably more likely to be involved in conflict. Conflict often arises when one group member shows aggression toward a close relative of another. Further, both males and females may redirect aggression towards individuals in which both had close relatives that were previously involved in a conflict. This suggests complex recognition not only of individuals, but also of associations between individuals. This does not suggest recognition of other's individual kinship bonds is possible, but rather that discrimination of social relationships does occur.

Reproduction

Female vervets do not have external signs indicating a menstruation period, thus there are not elaborate social behaviors involving reproduction. Typically, a female gives birth once a year, between September to February, after a gestation period of about 165 days. Usually only one infant is born at a time, though twins can occur rarely. A normal infant weighs 300–400 g.

Food

The vervet monkey eats a primarily herbivorous diet, living mostly on wild fruits, flowers, leaves, seeds, and seed pods. In agricultural areas, vervets become problem animals, as they will raid bean crops, peas, young tobacco plants, vegetables, fruit, and various grain crops. Carnivorous aspects of their diet include grasshoppers and termites. Raids of cattle egrets and weaver bird nests have been observed where the vervets will eat the eggs and chicks.

A list of some natural food plants and part of the plant eaten, in South Africa:

⤷  "Acacia erioloba" – seeds and pods
⤷  "Aloe spp" – nectar
⤷  "Celtis africana" – fruit
⤷  "Colophospermum mopane" – seeds
⤷  "Deinbollia oblongifolia" – fruit
⤷  "Euphorbia ingens" – fruit
⤷  "Euphorbia tirucalli" – fruit
⤷  "Ficus abutifolia" – figs
⤷  "Ficus sur" – figs
⤷  "Ficus sycomorus" – figs
⤷  "Grewia caffra" – fruit
⤷  "Harpephyllum caffrum" – fruit
⤷  "Hyphaene coriacea" – fruit
⤷  "Phoenix reclinata" – fruit
⤷  "Protorhus longifolia" – fruit
⤷  "Rhus chirindensis" – fruit
⤷  "Sclerocarya birrea" – fruit
⤷  "Strelitzia nicolai" – soft parts of the flowers
⤷  "Ximenia caffra" – fruit
⤷  "Ziziphus mucronata" – fruit