Chlorocebus sabaeus
green monkey

Chlorocebus sabaeus (the green monkey) is found almost exclusively in West Africa. It ranges from Senegal to the White Volta River in Ghana and can be found in many other African nations. Chlorocebus sabaeus was introduced to the Caribbean islands during extensive slave trading in the 1600s. These islands include St. Kitts, Nevis, and Bardados. (Cawthorn Lang, 2001; Zinner, et al., 2009)

Although green monkeys prefer specific environmental conditions, they easily adapt to a wide range of habitats. In Africa, green monkeys live south of the Sahara Desert in forests that border woody grasslands. These areas are normally characterized by low, bushy foliage and tall grasses. Green monkeys live near the edges of these transitional forests and can be found crossing savannas between forest edges. They avoid the interior of dense, wet forests. Green monkeys also have colonized coastal regions of West Africa, although this is a deviation from habitat norms. Recent habitat destruction and deforestation are thought to have contributed to these recent migrations. In the Caribbean, green monkeys occupy a variety of habitats including mangrove swamps, agricultural sectors, and highly populated urban settings. (Cawthorn Lang, 2001; Dunbar, 1974; Wolfheim, 1983; Zinner, et al., 2009)

These medium-sized monkeys are covered in thick golden fur with a green tint, which is how they get their common name, green monkeys. The face is hairless, but is covered with dark blue skin outlined by a soft line of white fur. Like other monkeys, they have long, slender, semi-prehensile tails. Males and females are sexually dimorphic. Males can weigh between 4 and 8 kg and measure an average of 500 mm in length. Adult females normally weigh between 3.5 and 5 kg and measure approximately 450 mm in length.

Males have blue scrotal regions and distinctly red penises. The combination of colors is said to present a distinctive “red, white, and blue” display.

Green monkey locomotion varies little, regardless of habitat or substrate. In almost all circumstances, they travel quadrupedally on the ground or in tree canopies. Being relatively light, green monkeys are able to nimbly travel on the tops of branches using all four limbs. (Cawthorn Lang, 2001; Skinner and Smithers, 1990; Young, 1998)

Green monkey social structure revolves around alpha males. These males control interactions and contact of males and females. The alpha male dictates which males mate with females in this polygynous mating system and dominate most of the matings. (Cawthorn Lang, 2001)

Green monkeys are seasonal breeders, breeding between April and June. In the area typically inhabited by green monkeys, these months are characterized by heavy rainfall. Abundant rainfall results in an exponential increase in available food and nutritional resources. It is thought that this particular breeding season is an adaptation to take advantage of abundant resources. Green monkeys breed approximately once a year. The time interval between each breeding attempt depends on the success or failure of the previous pregnancy. Females reach sexual maturity in 2 years and males in 5 years. Infant mortality is high, resulting in a loss of about 57% of all newborns. (Cawthorn Lang, 2001; Cheney, et al., 1988; Fairbanks and McGuire, 1985; Young, 1998)

From birth, mothers are closely attached to their offspring. Mothers tend to their offspring for approximately 1 year until they are fully weaned and independent. (Cawthorn Lang, 2001; Cawthorn Lang, 2001)

The lifespan of green monkeys has not been well studied. Green monkeys are heavily preyed on and affected by a variety of diseases. In captive conditions the lifespan ranges from 11 to 13 years. This is assumed to be the upper limit for age of green monkeys in the wild. (Fairbanks and McGuire, 1985)

Green monkeys are highly social. Grooming behaviors and gender relationships suggest underlying social hierarchies. Total group number can vary greatly, from 7 to 80. Male and female green monkeys partake in inter-group emigration. After reaching sexual maturity, adults move from group to group with closely related family members. This helps to avoid predation, reduce inbreeding, and increase the spread of desired genes. Small overlaps of green monkey territory exist in many habitats. Alpha males establish dominance through physical fighting or scrotal displays. Dominance rank determines access to mates and resources. Green monkey alpha males limit the proximity of other males to females and defend their territory with physical aggression against alien males. Such encounters typically are limited by environmental conditions and resource availability. It is only when food or habitat becomes scarce that territorial encroachment occurs. (Cawthorn Lang, 2001; Cheney, et al., 1988)

The home range of green monkeys has been estimated at from 0.05 to 2 square kilometers. (Zinner, et al., 2009)

Green monkeys are very vocal primates. Vocalizations serve mainly to alert local members to danger. Using distinct vocalizations, green monkeys are able to differentiate among various predators and levels of danger. Green monkeys have evolved a unique call for each predator. Males are also capable of communicating through body language. Using brightly colored genitalia, green monkeys can signal danger to other monkeys without vocalizations. This form of non-verbal communication is also a method of establishing social hierarchies and male dominance. A more subtle mode of communication is through facial expressions. Research demonstrates that facial expression is correlated with emotional state. Feelings of anger, elation, and even frustration are manifested in distinct facial expressions. It is possible that green monkeys use facial expressions to indicate danger or satisfaction, depending on the circumstances. (Cawthorn Lang, 2001; Cheney, et al., 1988; Peters and Ploog, 1973; Skinner and Smithers, 1990)

Green monkeys are both frugivorous and folivorous depending on the availability of leaves and fruit. Green monkeys adapt to available resources depending on the time of year and environmental conditions. During the dry season or after a fire, little fruit is available. Green monkeys forage across short expanses of grassland eating available plants. Nonetheless, fruits are preferred to leaves and less nutritious grasses commonly found in savannas. When rain is plentiful, fruits become more abundant. Fruits typically are collected in the trees and common fruit species eaten include wild bananas, papayas, and mangos. In the wild, green monkeys commonly use a mouth pouch to store and carry food as it is found. These pouches are present in all members of the Cercopithecoidea. This behavior protects valuable food from other consumers and allows green monkeys to continue collecting food for extended periods. (Dunbar, 1974; Young, 1998; Dunbar, 1974; Young, 1998)

In West Africa, leopards, martial eagles, and pythons are primary predators of green monkeys. In the Caribbean and the West Indies, humans are the only documented predators. (Cawthorn Lang, 2001)

Very little is known about the ecosystem role of green monkeys. However, they are highly frugivorous and likely play a large role in spreading seeds throughout the ecosystem. Also, their herbivorous diet competes with that of insects, birds, bats, and other species of primates. The large population density of green monkeys makes them accessible to many predators. Thus, they are a valuable source of food for other organisms including African cats, predatory birds, and sometimes baboons.

Documented cases of green monkey parasites are prevalent. Protozoan parasites and helminths (parasitic worms) are the most common and harmful organisms that plague green monkeys in the wild. (Bourliere, 1985; Legesse and Erko, 2004)

Green monkeys and related species have been used extensively in biomedical research. Many studies have been conducted on the effects of infectious diseases on primate biology. Most notably, valuable advances in HIV/AIDS can be directly connected to experiments performed on green monkeys. (Carlsson, et al., 2004)

In West Africa, humans rarely come into contact with green monkeys. In the Caribbean, green monkey populations have expanded due to a lack of natural predators. There, they are crop pests, foraging on fruit and other crops. (Boulton, et al., 1996; Cawthorn Lang, 2001)

Although green monkeys are not considered endangered, it is feared that continued hunting, trapping, and habitat destruction will drive populations to low levels in their native range in Africa. Continued research is being conducted in order to better understand the ecology of green monkeys and how to protect populations. However, in the Caribbean, where they are introduced, green monkeys are considered pests and populations have become dense in some areas. (Boulton, et al., 1996; Cawthorn Lang, 2001)

The taxonomy of green monkeys has recently been a topic of discussion. In the past, green monkeys and their close relatives were included in the species Cercopithecus aethiops. However, recently green monkeys received specific status. The generic name Cercopithecus is still mistakenly used in reference to green monkeys occasionally and is the name that was used in older literature. (Rowe, 1996; Cawthorn Lang, 2001; Rowe, 1996)