Monkeys of the Savannah

Monkeys of the Savannah - Vervets

The Vervet Monkey belongs to group of monkeys known as ‘guenons' which belong the large genus Cercopithecus (28 species). Some authors divide the vervet into four species, depending on their geographic location and coat colour, but all are very similar. Unlike all of its close relatives which depend upon forest, the vervet is a monkey of African savannas. It spends much of time in trees, favouring acacias along rivers or drainage lines. It is the most widespread of African monkeys, occurring throughout the northern and southern savannas, from the southern Cape north to Sudan and Senegal.

Food and Foraging

Like many primates, the vervet is an opportunistic, omnivorous feeder. Fruits, seed pods, sap, flowers, fresh shoots, grasses and vertebrates such as reptiles, insects and nestling birds, are among the most common food items. They quickly adapt to human settlements and habitually raid orchards and even household kitchens. They can become a pest at camps and lodges in wildlife reserves, if visitors feed them or if food is left in open situations. Troops forage in trees or on the ground. When moving, the monkeys disperse over a reasonable area and move slowly on a broad front. Activity slows down in the heat of the day, with peak feeding times in the early-to-mid morning and mid-to-late afternoon. In the late afternoon, the troop retires to a favoured roost site, such as a tall Fever Tree, where they will spend the night.

Life in the Troop

Troop size varies depending upon the habitat and food sources available, but usually ranges between 8 and 50 individuals. Twenty or so is probably the average. Vervet troops are essentially groups of families each of which has a hierarchy in the social order. The offspring of high ranking females are accorded a position just below their mother's and gain priority for food above adults of a lower ranking family. One or more adult males - immigrants from other families - are key members of the troops. The males are vigorous in defence and have mating ‘rights' over mature females. Adult males are able to dominate adult females in personal encounters, but if a female feels threatened, a simple squeal or cry will bring other females to the scene, causing the male to back off. Young, non-dominant males transfer to other troops, thus avoiding inbreeding with their siblings. Senior females usually lead troop movements.

Reproduction is seasonal, with most infants being born at the beginning of the rainy season when food is most plentiful. There is no pair bond between males and females, but it is unusual for females to mate with more than one male in a day. In northern Tanzania, female vervets have been observed to display colourful genitalia when on heat, matching the vivid blue scrotum of the male. This condition of readiness has not been reported throughout the vervet's range, however, and there generally appears to be no external indications of oestrus (as, for example, occurs in baboons and chimps). Mating usually takes place on the ground, with the male standing upright behind the female. Pregnancy is about 165 days (5.5 months) which is much longer than for any other similarly sized monkey.

Predators Beware

Since they spend a fair amount of time on the ground, vervets are vulnerable to a host of predators. Leopard, Serval, Caracal, Martial Eagle and Crowned Eagle are the principal enemies, although Lion, Cheetah, Rock Python and Nile Crocodile all pose a threat. Infants are safe when in the arms of their mother, but juveniles may be taken by smaller eagles and larger hawks. Baboons sometimes feed in association with vervets, when a cunning male is capable of killing and eating a vervet. Interestingly, vervets have different alarm calls for avian and ground predators and their unique clucking bark is often used successfully by safari lodge trackers to locate leopards for guests! Snakes elicit a different alarm call from vervets.

-Duncan Butchart-

Posted: Mammals by CC Africa, Date: 21 November 2006