GRAY-CHEEKED MANGABEY

Lophocebus albigena

Geographic Distribution and Habitat

The gray-cheeked mangabey, also known as the white-cheeked mangabey, can be found in the forests of Central Africa, from Cameroon in the north to Gabon in the south. These large monkeys are almost completely arboreal and rarely come to the ground. They prefer to use the upper to middle layer of the canopy as they travel from tree to tree looking for food. Mangabeys are adapted to live in different types of forests including dense tropical forests, secondary forests that have been disturbed by human activity, and swamps with scattered trees.

TAXONOMIC NOTES

Mangabeys can refer to two different clades or groups of primates. One clade is the Cercocebus, which is a more terrestrial (ground-dwelling) group of monkeys that look like mandrills, while the other is the Lophocebus, which is a more arboreal (tree-dwelling) group of monkeys that resemble baboons. It is difficult to clearly lay out the taxonomical differentiation between mangabeys because they share a lot of common features such as similar body shapes, skull sizes, teeth thickness, and diet.

There are four subspecies under Lophocebus:

Gray-cheeked mangabey (Lophocebus albigena albigena)
Johnston’s mangabey (Lophocebus albigena johnstoni)
Rusty-mantled mangabey (Lophocebus albigena osmani)
Ugandan Crested mangabey (Lophocebus albigena ugandae)

The subspecies have slight variations in the hair color around their head, with colors ranging from dark brown to yellow.

Size, Weight, and Lifespan

Adult male gray-cheeked mangabeys are larger than females. Both sexes sport tails that are twice as long as their body. The length of their body is 17–29 inches (45–73 cm) in males and 20–22 inches (50–56 cm) in females. Tail lengths are 29–39 inches (73–100 cm) in males and 26–31 inches (67–80 cm) in females.

Adult gray-cheeked mangabeys weigh about 20 pounds (9 kg). Males weigh between 13 and 20 pounds (6–9 kg) and females weigh 10–14 pounds (4.5–6.5 kg). They rapidly gain this weight from 0.9 pounds (425 g) at birth to 4.7 pounds (2170 g) about 7 months later when they stop feeding on their mother’s milk and start eating whole foods.

The maximum recorded age of a captive female gray-cheeked mangabey was 36 years, so in the wild we expect gray-cheeked mangabeys to live into their twenties. Female gray-cheeked mangabeys live longer than males, which is common among primates. Unlike most primates, in gray-cheeked mangabeys, younger mothers tend to have offspring that live longer. So it seems that there is an optimal or ideal age for mothers to raise offspring successfully, where mothers have adequate experience in birthing and raising young, but she is also young enough that the genetic material of their eggs is still intact.

What Does It Mean?

Clade:
A group of animals derived from a common ancestor species.

Gestation Period:
The time of pregnancy from conception until birth.

Visit the Glossary for more definitions

Appearance

Gray-cheeked mangabeys are fairly large, long-tailed monkeys with thick fur on their body. Their head and faces seem small compared to the rest of their body. They have distinctive tufts of hair around their face, which looks like each mangabey has his or her own punk hairdo. They are mostly black on their heads and legs while their back and shoulders are more gray or brown depending on the individual or subspecies. As their name suggests, their face is covered in short gray hairs and their cheeks can sometimes look whitish.

Newborns have cute, pink, wrinkly faces with large eyes. Over the next six months, these wrinkles smooth out and their face becomes browner. At this stage, young gray-cheeked mangabeys develop tufts of hair around their face similar to that of fully-grown adults.

Diet

Gray-cheeked mangabeys are mostly frugivorous (fruit-eating) and prefer to eat from fig trees that produce a lot of nutritious fruits. They are so dependent on figs that the months in which fruiting figs are most productive correlates with higher numbers of new births. When fruits are not in season, these mangabeys will also feed on insects, small animals, flowers, and seeds. Their ability to thrive in different landscapes comes from their ability to live on a varied diet.

Gray-cheeked mangabeys have powerful jaws and teeth, which they use to break open tough nuts and seeds that other smaller-toothed primates cannot eat. As a result, there are a lot more food choices available to them and they can switch between different types of food if one type runs out or if there is too much food competition.

Behavior and Lifestyle

Gray-cheeked mangabeys are excellent at jumping through the forest canopy and they use their long tail for balance as they travel. They are diurnal and spend a lot of their day traveling to find good quality food sources. They are quite picky about their fruit and take time to inspect the fruits for their ripeness and quality before settling to feed at a tree. They are more likely to go back to a tree that gave them a positive feeding experience rather than trying the fruit of less familiar trees. We can imagine there are plenty of people like that too, who would rather drive further to their favorite restaurant rather than go to someplace closer that they haven’t eaten at previously. In fact, some researchers are using the mangabey’s foraging strategies to understand how humans may have developed our ability to solve larger problems.

When gray-cheeked mangabeys encounter predators like crowned eagles, males emit alarm calls to alert the entire troop. However, males will only actively chase the eagle, and endanger their own safety for the sake of the troop, if there are youngsters to protect. Males who chase predators are more likely to be caught and eaten by the predator. This means that male gray-cheeked mangabeys are aware of the risk of chasing eagles and are only willing to take the risk to protect their offspring.

Fun Facts

Gray-cheeked mangabeys have an iconic “whoop-gobble” call that can be heard from half a mile away.

Males spend more time arguing and fighting. Females are more peaceful.

Mothers protect their daughters more so than their sons.

Male mangabeys are more likely to fight off predators if there are baby mangabeys in the troop.

Daily Life and Group Dynamics

Gray-cheeked mangabeys live in multi-male, multi-female groups with about 6–30 individuals. Larger groups have to find more resources and end up traveling longer distances than smaller troops. The home range for these primates can range from 32–988 acres (13–400 ha).

Males and females have separate ranking systems within a troop. A dominant, or highest-ranked, male will have more mating opportunities than other males. The highest-ranked females will have more access to food resources, especially when food resources are low.

When male gray-cheeked mangabeys reach sexual maturity, they disperse from their natal troops (the troop they were born into) to join other troops, usually as subordinate males. In many primate species, males may move from their natal troop to bachelor groups with their brothers or troops with close male relatives such as uncles or cousins. This has not been seen in gray-cheeked mangabeys who do not go out of their way to look for relatives in a troop before joining it as a subordinate male.

Subordinate males will challenge dominant males to gain access to females in the troop. In gray-cheeked mangabey societies, males tend to have lots of little fights amongst themselves throughout their day, while females are more peaceful with each other. Females spend a lot of time allogrooming (grooming each other) which strengthens the positive bonds between them. Males, on the other hand, do not engage in much allogrooming.

Female gray-cheeked mangabeys stay with their natal troop for their whole lives, where they maintain strong bonds with all the other females in their troop. Primatologists use the term “female bonded” to describe this group dynamic. A female gray-cheeked mangabey forms the strongest bond with her closest female relative, such as her mother or sister. There is also a hierarchy, or a dominance rank system, where older females have more authority or power in the female group. Studies indicate that female dominance hierarchies influence important ecological aspects of how individuals deal with food competition and how far they travel to forage.

Communication

In the forests of Central Africa, you will probably hear the gray-cheeked mangabey before you see them. Adult gray-cheeked mangabeys give a loud low-pitched “whoop-gobble” call that can be heard from over 0.5 miles away. The gray-cheeked mangabey has a specialized sac structure in their throat that vibrates when they make these loud calls.

The “whoop-gobble” call is associated with particular facial expressions and behaviors. When they make the “whoop” part of a call, their body jerks forward and they are usually looking in a particular direction with tense, hooded eyes. After a 5-second pause, the gray-cheeked mangabeys start the gobble portion of their call, which lasts for three seconds. During the “gobble” call, they raise their head and move their shoulders up and down in a rapid shrugging motion.

Gray-cheeked mangabeys use the long-distance whoop-gobble sound to alert other troops of their presence. Once a troop hears this call, they can choose whether to approach the neighboring troop and or withdraw. Confronting a neighboring troop can result in conflicts and aggression over food sources or mates. Close-range conflicts are noisy events with a lot of chasing, screaming, and grunting by all troop members. Males are the biggest participants in these conflicts while females are chased away from the fight.

Reproduction and Family

Gray-cheeked mangabeys do not have a specific mating season. Instead, female hormone levels set the rate of reproduction. When the female reproductive hormone, known as estrogen, gets high enough in females, they will be ready to mate. As estrogen increases, the female sexual organs will swell until they become large and pink, at which time she is said to be “in estrus.” This swelling is a signal to males, telling them that she is ready to mate and will probably have offspring. As the estrogen levels decrease in the female, her swelling decreases and she will not accept mates. The swelling in females lasts for about 17–38 days with estrogen being at the highest level for 2–4 days when the chances of her getting pregnant are also the highest. Dominant females come into estrus and give birth sooner than lower-ranking females.

The dominant male will get the most opportunities to mate with the females. However, lower-ranking males will try to be sneaky and mate with females while the dominant male is away or distracted.

The gestation period is 4.4 months and females give birth to one offspring every three years or so. One interesting study showed that gray-cheeked mangabeys had more offspring in months when fig fruits were most abundant. There may be a link between the availability of these highly nutritious fruits and increased fitness in mothers.

The strong female bonds in gray-cheeked mangabeys are developed as soon as a daughter is born. Mothers are more protective of daughters than sons.

Ecological Role

As with most frugivorous primates, gray-cheeked mangabeys play an important role in seed dispersal and help growth of fruiting trees. And because gray-cheeked mangabeys eat different kinds of fruit, they can influence the regeneration of different species of fruit trees in their environment.

Gray-cheeked mangabeys may act as pollen-transporters or pollinators. They spend a lot of time among flowers, occasionally feeding on them, and end up getting pollen on their faces and hands. Eventually, the pollen-covered mangabeys will move to the next branch or tree and transfer the pollen to another flower. This allows trees or flowers that are far apart to reproduce. Certain tree species need pollinators to survive and without animals like the gray-cheeked mangabey, the forest would not be the complex ecosystem it is.

The gray-cheeked mangabey is an important link in the food chain of their forest ecosystem. Gray-cheeked mangabeys are a major food source for crowned eagles. One study of crowned eagle droppings revealed that most of the eagle’s diet consisted of male gray-cheeked mangabeys, probably because males are most likely to confront predators to protect the troop.

Conservation Status and Threats

The International Union for Conservation of Nature lists the gray-cheeked mangabey as Vulnerable (IUCN, 2017), appearing on the IUCN Red List of Threatened Species.

While these primates are capable of living in different environments, gray-cheeked mangabeys depend mostly on forest trees to provide food and cover. Their populations in many parts of their home range is decreasing because forests are being cut down for lumber, and space for agriculture. Additionally, gray-cheeked mangabeys are hunted for bushmeat because their large size makes them easy targets. Uncontrolled bushmeat markets can have devastating effects on local populations. In countries where is there war and political instability, wildlife species that are hunted for food (subsistence hunting), such as the gray-cheeked mangabey, are especially vulnerable to population declines. Gray-cheeked mangabey populations have been declining over the last 30 years.

Conservation Efforts

The gray-cheeked mangabey is listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival. The Appendix II listing indicates that the population is not threatened with extinction, but trade should be controlled to avoid severe declines in the population.

Gray-cheeked mangabeys are also given protection under Class B of the African Convention on the Conservation of Nature and Natural Resources which is a treaty among African nations to promote environmental protection through environmental laws. The Class B designation means that the gray-cheeked mangabey is protected on the continent but they may be hunted or captured if national governments supply specific permits.

The best efforts to protect the gray-cheeked mangabeys are habitat protection and conservation programs within their home range. In protected reserves such as Dja Faunal Reserve and Lobéké national park in Cameroon and Minkebé national parks in Gabon, habitat is generally preserved and free from development.

References:

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Written by Acima Cherian, November 2022