Dave Taylor's African Safari: Trophic Level III: Omnivores and Small Carnivores - Primates (Omnivores): Vervet Monkey

Trophic Level III: Omnivores and Small Carnivores
Primates (Omnivores): Vervet Monkey
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Primates are made up of several orders. Included are lower primates (prosimians), represented in the Serengeti-Mara by the bushbaby and the greater bushbaby or galago. Bushbabies are only found in Africa.

Primates also include the monkeys and the apes. All primates have relatively large brains and forward facing eyes. There are several species of monkeys in the Serengeti-Mara, but no apes.

The primate family also includes our species, Homo sapiens sapiens.

Vervet Monkey
Cercopithecus aethiops

Length: 38-61 cm (15 - 24 inches)

Tail: 42-114 cm (16 - 45 inches)

Weight: 2.5-6 kg (5.5- 13 lb.) female, 3.5-9 kg (7.7-20 lb.) male

Status: Very abundant

Habitat: Vervets live in all varieties of woodlands. They are especially common along the grassland edges of forests. It is one of the few monkeys that leave the rainforest to forage in the grasslands but still seeks trees for safety.

Vervets are often found where riverine forests and fever trees grow.

Food: Vervets are omnivores and eat a wide variety of food. Included in their diets are gum, new leaves and thorns (before they harden), flowers, seed pods, peas, powdery bark, and even wood. They eat the most abundant fruits, seeds, flowers and grasses.

They will eat insects, centipedes, lizards, bird's eggs and nestlings. Insects, herbs and grasses are mainly consumed in the wet season.

Vervets are very important to the ecology because they disperse seeds in their droppings.

Social System: Vervets are social animals that live in troops. The numbers of animals in a troop vary. In a rich habitat, troops average 11 monkeys (2 adult males, 4 adult females and 5 young). In poorer habitats, the troop size ranges from 8 to 50 animals (average 25). In the richer locations, the area needed to feed the monkeys is much smaller and the population density much higher (89 per square kilometer or 230 per square mile). In the poorer area, the territories are two to ten times larger which means that the animals have to travel much further to find enough food. The population density is much lower in this area.

A vervet troop consists of family groups of females and young. Together, they share and defend a range. Males that join this group also defend the territory against other males. Males within the group must also compete to establish their dominance over other males in order to obtain breeding rights with females.

A Place To Call Home

Both sexes scent mark their territory by rubbing their chests on branches and other objects. Males will also sit facing other troops in such a way as to display their colorful genitals. This alerts other rival males that a dominant male is on guard.

The females, too, have a rank order. Infants assume their mother's rank upon birth. A high ranking daughter will be able to dominate daughters of lower ranking females and will eventually take her mother's place. Even adult females will give way to a high ranking female’s daughter.

The advantage of rank is obvious. The higher up an animal is, the greater its access to resources. High ranking females get to drink from the safest place at the waterhole, they get the best feeding and resting spots. Lower ranks are forced to choose poorer (and often more dangerous) locations.

Lower classes groom higher ranking individuals.

Male vervet monkeys must leave their troop when they mature. They leave when they are two to three years old. Dominant males in their own troop constantly harass the young males and eventually force them out. Male vervet monkeys develop a bright blue scrotum which acts as a visual sign to females indicating their maturity and breeding status. As the juveniles develop this feature, it irks the dominant males more and more. Not surprisingly, most juvenile males leave their group during the mating season when dominant males are at a peak of aggressiveness.

Leaving Home

When a young male leaves his troop to seek residence in another, he must do so with great care. There is little difference between his size and that of the females in the new troop. If he is too bold he will annoy not only the dominant males, but the females as well. Both sexes will attack and chase him off.

Males can lesson the risk of attack by immigrating with their peers or by joining a troop which contains an older brother.

Troops which exchange males are less hostile towards each other than troops that do not share any relations.

Males may be forced to move again if they cannot successfully join the first troop they approach.

Behavior: Female vervets usually mate once a day. Mating is not confined to estrus and takes place all year round. Most females mate only with dominant males but there is no pairing. Over the year, she may mate with several different males. In most vervet populations, unlike female baboons, there is no external sign of estrus.

Most females produce one young per year. They first breed when they are 3.5 to 4 years old. Males breed one year later. Gestation is 165 days.

Young vervets are well developed at birth. Their eyes are open and they can cling to their mother's chest. Mothers will let companions hold their babies. Other young monkeys as well as adult females all seem to want to hold the baby. Adult males show no interest at all in the babies.

Within a few weeks, the infant is playing with other vervets its own size as well as its babysitters. For the first three months, it is very dependent on its mother. By four months of age, it is being weaned and no longer rides on its mother's chest or back. By six months, it is fairly independent but it will run to its mother if it is bullied.

Predation: Many species prey on vervets. Large eagles, leopards, serval, cheetah, lions and snakes are their main enemies. Foraging on the savanna makes them more vulnerable to attack. They seldom stray more than 300 meters (300 yards) from the safety of trees.

Vervets possess a well developed language with over 60 distinct physical gestures and 36 distinct sounds. Not surprisingly, many of these sounds relate to predators.

Uh. A low-intensity response to a minor predator such as a rock python or black-backed jackal.
Chirp. A short, sharp call that carries far. This is made when a major mammal predator such as a lion or leopard is near.
Rraup. A rough, short call given once when an eagle or other bird of prey is spotted. The troop responds by seeking cover on the ground. This is given by females and young.
Threat-bark alarm. Given by males, the tempo and volume of this call increase as a predator gets closer.

Vervets are often seen near baboons. Baboons are the more dominant of the two species and get all of the best feeding locations except those farthest out on the branches. Baboons will sometimes prey on young vervets but adults monkeys can easily escape them.

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