Considered intermediate in form between the more arboreal guenons and the terrestrial patas monkey (Erythrocebus patas), the vervet readily runs and forages on the ground, and is a good swimmer, but also depends on trees for food, sleeping sites and shelter from danger. This species is mainly active by day, and feeds on a wide range of items, including fruit, seeds, buds, leaves, roots and grasses, as well as insects, crustaceans, birds’ eggs and chicks, and other small vertebrates, such as lizards (2) (4) (5) (6) (8). The vervet will also bite into and chew trees such as acacias, to feed on the sap (4).
Vervet groups usually range in size up to about 38 individuals (1) (6), and include several adult males (1) (2) (4). Within the group there is a clear dominance hierarchy, and activities such as grooming help maintain group cohesion (4) (5) (6) (9). A female’s social rank usually determines the rank of her offspring (4). The female vervet usually gives birth annually, to a single young, or rarely twins, after a gestation period of around 5.5 months (2) (4) (5) (6). In any given vervet population, there is typically a peak of births that coincides with the season when resources are most available (2) (4). The young vervet is weaned by about 8.5 months (2), and females reach maturity at around 2.5 to 4 years, remaining within the group for life, while young males reach maturity after about 5 years, and then leave to join another group (2) (4) (6). Lifespan may be up to 30 years (2) (7).
The vocal communication of the vervet has been the subject of many studies. The species is vulnerable to a range of predators, including leopards, eagles and snakes (6) (7), and has been found to produce different alarm calls in response to different types of predator, with each call producing a distinct response. For example, the group will respond to a ‘leopard’ alarm call by running into the trees, and to an ‘eagle’ alarm call by looking up (10). Studies have so far identified at least 36 distinct calls (2) (4), and the vervet has also been shown to be able to identify other individuals by their calls (4).