Official Common NameVervet monkey
Derivation of scientific name
Commonly called vervet monkeys, or just vervets, Cercopithecus means ‘long-tailed monkey’. Sometimes, in literature, this species is lumped with Cercopithecus aethiops, which means ‘Ethiopian long-tailed monkey’.
Notes on Taxonomy
The vervet monkeys were placed in the genus Chlorocebus (meaning ‘green monkey’) by Grooves (2001) and he recognised six species in Africa: Ch. aethiops, Ch. cynosuros, Ch. djamdjamensis, Ch. pygerythrus, Ch. sabaeus, and Ch. tantalus, of which Ch. aethiops was recorded as occurring in southern Africa. However in a subsequent revision, Skinner & Chimimba (2005) retained the vervet monkey in the genus Cercopithecus. They argued that the status of aethiops is still somewhat confused in the literature, and until a consensus is reached it should be retained as a superspecies in Cercopithecus and with five sub-species C. (a.) aethiops, C. (a.)djamdjamensis, C. (a.) pygerythrus, C. (a.) sabaeus and C. (a.) tantalus, of which C. (a.) pygerythrus is the vervet monkey, which occurs in southern Africa. For the purposes of this assessment this taxonomy is adopted, and the vervet monkey of southern Africa is therefore referred to as Cercopithecus pygerythrus.
Vervet monkey [English], blouaap [Afrikaans], inkawu [isiZulu and isiNdebele], kgabo [Setswana and Sesotho], ngobiyana [siSwati], nkawa[Xitsonga] and thoho [Tshivenda].
Vervet monkeys are medium-sized primates that are highly social and live in groups of up to 50 individuals. Within a troop, adult males form a dominance hierarchy that is established and maintained by threat and aggression. Facial expressions (eye lid display) and body postures are used to communicate threats or aggressive behaviour. At sexual maturity, young males tend to migrate between groups – usually in the company of a sibling or peer. In contrast females remain in their natal groups and form strong hierarchies that are based on maternal social status. Vervet monkeys are largely vegetarian and are common in savannah and woodland that have access to water and trees for cover. Vervet monkeys can be serious pests that cause crop damages in areas where their habitat overlaps with agricultural areas. Vervet monkeys are classified as Lower Risk/Least Concern by the IUCN due to their wide range.
How to recognise avervet monkey
There is considerable variation in body colour among vervet monkeys that occur in southern Africa, but they can generally be recognised easily by their grizzly, silver-grey coat, black face and long tails. The vervet monkey’s face is black with white colouring around the eyes and on the eyelids. The face, hands and feet are hairless and black. Males have brightly coloured genitals with a blue scrotum and a red penis. Vervet monkeys have long arms and legs that are of approximately equal length. The males are larger than the females and range from 420 to 600 mm in height and from 3.9 to 8.0 kg in weight, while the females range from 300 to 495 mm in height and around 3.4 to 5.3 kg in weight. Vervets have long canine teeth, which protrudes about 3.2 cm from the gum. Babies are dark with pink faces. Females have one pair of mammae on the chest.
The vervet monkey moves on all four limbs both on the ground and in the trees. It only occasionally leaps from tree to tree. It descends trees in a head first manner. The fastest gait, or mode of locomotion, is a bounding gallop on all of its limbs. Vervet monkeys are also capable of swimming.
Vervet monkey calls can be grouped into three categories: wanting, aggression and alarm. Wanting calls include medium-intensity, drawn-out gargles by mothers to attract their infants, while aggression or irritation is signified by chattering. High pitched squeals indicate distress and vervet monkeys can communicate the presence of different predators by using different calls. Each alarm call results in a different response appropriate to avoiding the specific predator. For example, leopard alarms are short tonal calls to which vervet monkeys respond by climbing into trees. Eagle alarms are low-pitched grunts to which vervet monkeys respond by looking up to the sky to locate the potential predator. Snake alarms are high-pitched chatters, to which and the vervet monkeys respond by searching the ground for potential predators.
Vervet monkeys occur throughout Africa, from Senegal in the west to Ethiopia in the east and all the way down south to the Western Cape in South Africa.
Vervet monkeys occur in a wide variety of woodland and open savannah, where they are dependent on water availability and trees for food and cover. They are generally absent from open grassland and scrub. They are also found in urban areas and farms were they often raid crops in cultivated fields.
Vervet monkeys are generally vegetarian and eat leaves, gum, seeds, nuts, grasses, fungi, fruit, berries, flowers, buds and shoots, but they are also known to feed occasionally on invertebrates, birds’ eggs, birds, lizards, rodents and other vertebrate prey. They have a strong preference for fruit and flowers, but they vary their diet according to seasonal food availability. For example, bushfires during the dry season often temporarily reduce vegetative food sources and vervet monkeys then exploit other food sources such as insects and rodents. In agricultural areas, vervet monkeys can become a serious pest that causes crop damage. They have cheek pouches for storing food. The vervet monkey’s colour vision allows it to distinguish between ripe and unripe fruit. They are dependent on water and must drink daily, which is why they prefer to be near a source of water.
SEX and LIFE CYCLES
Vervet monkeys are seasonal breeders and mate during a specific time of the year. The mating season varies somewhat with geographical location, but occurs between April and June and offspring are born after the rainy season, when there is plenty of food available. Females are sexually mature at four years and give birth for the first time around the age of five. In captivity, females mature more quickly and can give birth at as young as two years of age. Female vervet monkeys show no external signs of ovulation and their reproductive cycle is about 32.5 days. Males reach sexual maturity at around five years of age, but do not achieve full adult weight until they are six years old; limiting the opportunity for mating before then. Vervet gestation lasts 163 to 165 days.
Vervet monkeys live in complex but stable social groups, called troops, numbering up to 50 individuals. Troops usually consist of multiple male members that may not be related. Within each group there is an order of dominance that is maintained by threat and aggression. Vervet monkeys use facial expressions (eye lid display) and body postures to communicate threats or aggressive behaviour. In vervet monkeys, the eye lids and adjacent areas have a light colouration that contrast sharply with the dark face. Retracting the eyebrows exposes these light areas and when this eye lid display is accompanied by a specific body posture (stare, crouching or upright body position) it functions either as a defensive or an aggressive threat. For example, a defensive threat display is associated with an eye display while the monkey is in a crouching position, while an eye lid display when the body posture is upright functions as an aggressive threat. Aggressive behaviour is also associated with thrusting head and body postures. Other displays include genital signals in male-to-male interactions that signify aggression, defence and avoidance. These include penile display by dominant males directed at subordinate males, and rump display by dominant males to subordinate males by displaying an erect tail, anal opening, scrotum and white fur tufts on the rump. The submissive male responds by crouching and uttering specific grunts. Vervet monkeys also spend much of their time (up to several hours per day) grooming each other. Grooming is used to reinforce social bonds, as well as to remove parasites and debris from the fur.
THE BIG PICTURE
Friends and Foes
Vervet monkeys are preyed on by leopards, snakes and raptors, and in some cases even baboons. As a source of food to certain predators, they may have an effect on predator populations and as occasional predators themselves, they may be able to control populations of small animals such as insects and birds.
Safety in numbers. Living in a large family group has its advantages. They can defend themselves and their young more effectively against predators and rival groups that may want to take over their feeding grounds. Their ability to sound the alarm for potential threats from the ground and air makes them very effective at avoiding predators. They have cheek pouches for storing food. The vervet monkey’s colour vision allows it to distinguish between ripe and unripe fruit.
Poorer world without me
Vervet monkeys play an important role in the environment and natural ecosystems. They act as an agent for seed dispersal. The seeds are ingested as food and pass through the monkey’s digestive system intact and are excreted some distance away from where they were originally consumed. It was found that vervet monkeys can play an important role as seed dispersal agents to rehabilitate disturbed areas, for example in dune mining rehabilitation projects in Richards’s Bay in KwaZulu-Natal, Vervet monkeys played a major role in the rehabilitation of these areas by ensuring that the indigenous vegetation was re-established in areas where the vegetation had been completely destroyed.
People & I
Vervet monkeys have been used for scientific research since the 1950s. They are still used to produce vaccines for polio and smallpox. They are also important in studying high blood pressure and AIDS. People use their skin to create traditional Zulu and Swati male clothes. Some people hunt them and sell the meat. As urban areas have spread and the natural habitat that they depend on has been removed and reduced, vervet monkeys have increasingly become a problem in some areas in South Africa. They raid dustbins and homes looking for food and damage plants and vegetables growing in gardens. Solving this human–monkey conflict in a way that is both effective and ethical is not easy.
Conservation status and what the future holds
Vervet monkeys are classified as Lower Risk/Least Concern by the IUCN due to their wide range.
There are two species of monkeys within the family Cercopithecidae that occur in southern Africa and these are the vervet monkey Cercopithecus pygerythrus and the Skyes’ or Samango monkey, C. albogularis. The two species are sometimes confused, but they can be differentiated based on body size, colour and habitat preferences. The Samango monkey is larger and darker in colour than the vervet monkey and it prefers dense, tall forest, while the vervet monkeys are predominantly found in savannah or in lower, coastal forest habitat. The two monkey species can further be distinguished from baboons, which form the other genera in the family Cercopithecidae, by their characteristic short muzzle, and their black faces conspicuously rimmed in white fur.
References and further reading
- Groves, C.P. 2001. Primate taxonomy. Smithsonian Institution Press, Washington DC, USA.
- Seyfarth, R.M., Cheney, D.L. & Marler, P. 1980. Vervet monkey alarm calls: semantic communication in a free-ranging primate. Animal Behaviour 28: 1070–1094.
- Skinner, J.D. & Chimimba, C.T. 2005. The mammals of the southern African Subregion. 3rd edition. Cambridge University Press, Cape Town, South Africa.
Lowveld National Botanical Garden