BLACK CRESTED MANGABEY
Geographic Distribution and Habitat
Black crested mangabeys, also known as black mangabeys, are distributed patchily across the rainforests of the Democratic Republic of the Congo. Their natural habitat ranges south into the gallery forests of northern Angola, but the mangabeys may be extinct in that region. Deforestation has reduced their native forests to islets amid large expanses of savanna and agricultural land. Within these islets, the mangabeys spend most of their time foraging in the trees between the middle and upper canopy. They prefer primary and secondary tropical forests—those mostly undisturbed by human activity or re-grown after clearing, respectively—though some groups can be found in swamp and gallery forests.
Size, Weight, and Lifespan
Black crested mangabeys weigh 9–22 pounds (4–10 kg); females are slightly smaller than males, but the difference is less pronounced than in other primate species. They tend to measure 15–28 inches (38–71 cm) long—their tails add significantly to this length, reaching up to 30 inches (76 cm). In the wild, black crested mangabeys live 20–25 years.
Black-crested mangabeys take their name from the antennae-like tuft of hair that protrudes from the top of their heads. Curly white whiskers frame their generous cheek pouches, in which they sometimes store food while foraging. Altogether, they strike one as little black versions of the Grinch. Their slender frames, paired with long arms and legs and opposable thumbs, are well-suited for rummaging through the trees, as are their sizable tails, which often stand upright like a question mark to assist with balance. They are covered from head to toe with a fittingly black fur coat.
Despite their apparent slimness, black crested mangabeys possess powerful jaws and sharp front teeth that allow them to feed on a variety of plants and animals, including fruits that are too tough for other monkeys. Their diet consists of many fruits, seeds, and nuts, as well as insects and small animals like lizards and snails. During some months, they consume a great deal of nectar.
Behavior and Lifestyle
Black crested mangabeys wake up just after sunrise. Most of their foraging activity occurs in the early hours of the day, during which they leap and scamper through the forest canopy in search of their dietary staples. Their nimble build allows them to move smoothly and quickly from tree to tree.
Like other primates, they are highly social, and thus engage regularly in activities that maintain group cohesion, establish contact, display or submit to dominance, and so on. Black crested mangabeys communicate vocally using specialized vocal sacs—the resulting sounds, especially those made by males, can be very loud. Grooming features heavily as a way to maintain hygiene and strengthen social bonds. Young mangabeys also play among themselves and with older members of their group.
At night, black crested mangabeys construct nests in the canopy, often in the fork of a tree. These are woven from branches, leaves, and twigs. Usually, the nests are built anew each night, but old nests will sometimes suffice if the mangabeys have returned to a previously foraged area. By sleeping high off the forest floor, black crested mangabeys avoid common predators like leopards, snakes, and African crowned eagles.
Black crested mangabey groups range from 10–20 adult males, females, and offspring, which may break into subgroups during foraging. These groups feature both male and female dominance hierarchies. Males acquire and maintain status through dominance displays like puffing out their chests, baring their teeth, mounting, aggressive vocalizations, and (when necessary) hitting and biting. Subordinate males respond by crouching, lowering their heads, and generally avoiding contact with their dominant counterparts. Hierarchies are less stark in females, but still present. Unlike males, for whom size and strength are most crucial to dominance, females tend to rank based on their age. High-rank females reinforce their status by initiating grooming with low-rank females—they will resort less commonly to aggressive displays. For both males and females, dominance means greater access to desirable mating opportunities and resources.
Male mangabeys, unlike females, leave their birth groups upon reaching sexual maturity. This behavior is called dispersal. Primatologists think dispersal provides several evolutionary advantages to black crested mangabeys; it reduces inbreeding and allows males to find groups with available females if opportunities in their birth group are limited.
While black crested mangabeys do not, as aforementioned, hunt or eat other primates, they react to the alarm calls of nearby primate species like Wolf’s mona monkey and the red-tailed monkey and interact with them regularly.
Black-crested mangabeys communicate through vocalizations, body/facial expressions, and olfactory markings. Certain vocalizations are used by all members of a mangabey group, while others are limited to particular individuals. One group-wide vocalization is a staccato bark, which primatologists sometimes compare to the braying of a donkey. Black crested mangabeys bark when they see predators (or clumsy primatologists) and may continue for up to 15 minutes. Whoop-gobbles, conversely, are restricted to adult males—they usually occur after intra/inter-group male conflict. All mangabeys grunt in various contexts, often to establish or maintain contact with their peers when moving to a new spot or greeting one another.
Dominance and submission displays, as mentioned in the above section, allow black crested mangabeys to communicate status and intentions to one another. Facial expressions provide helpful cues for emotional states—for example, head-bobbing or staring with an open mouth seems to signal aggression, and females pout to indicate sexual receptivity. Olfactory marking assists the latter purpose as well—males will sniff the genitals of a female to determine if they’re ready to mate.
The menstrual cycle of female mangabeys lasts around 30–35 days. They’re sexually receptive for 2–3 days in this span–during this estrus period, red swellings on their hindquarters indicate their availability to males. Males compete for access to receptive females by beating their chests and fighting among themselves. The victors—usually dominant males—get preferential access to females. After mating, they’ll often guard them to prevent other males from mating. Nonetheless, females regularly mate with multiple males during estrus, including subordinate males.
Pregnancy lasts 5–6 months. At birth, a baby mangabey weighs 1–1.3 pounds (.5–.6 kg) and is covered in black fur. Their hands, feet, and facial skin are notably pale—these darken over time. Infant mangabeys spend most of their time during infancy clinging to their mother’s belly and depend on her for food and protection from predators and male mangabeys (who sometimes commit infanticide). Male mangabeys do not assist with childrearing, aside from occasional grooming or playing. Siblings, especially female siblings, may help their mothers track and feed their young. Alloparenting—when unrelated females assist with childrearing—is also common.
After a few weeks, mangabey infants start exploring their surroundings and may sample solid foods. They stop nursing around 6 months.
Black crested mangabeys are crucial for seed dispersal; by eating copious amounts of fruits and seeds, they spread various plant species all over their local forests. Importantly, they tend to toss fruit to the ground after taking one bite—species on the forest floor thus find themselves with an inadvertent food source. Eagles and leopards also commonly prey on black crested mangabeys.
The International Union for Conservation of Nature lists black-crested mangabeys as Vulnerable (IUCN, 2018), appearing on the IUCN Red List of Threatened Species.
Intense, uncontrolled hunting is a threat—black crested mangabeys are highly desired as meat and they present an attractive target for hunters due to their large size (relative to other monkeys). Poaching has intensified as much of the forests in their range have lost large mammals to hunting. Black crested mangabeys are facing a similar fate. Because of their relatively large body size, they are more attractive to hunters than the smaller guenon monkeys with which they share their range.
Habitat loss is another threat to black crested mangabeys populations. Since they spend most of their time in the trees, logging strands them in increasingly small areas of forest, as they cannot survive in the earth-bound savannahs and agricultural regions generated in the wake. The number of mangabeys that a forest can sustain thus decreases, leading to local extinctions in some areas—the remaining population in Angola, for instance, is on the edge of extinction.
Over the past 30 years, the mangabey population has dropped by 30%.
The black crested 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.
Establishing protected areas, as the United Nations has in places like Songa National Park, allows mangabey populations to regrow and prevents further encroachment on their habitats by logging and other agricultural efforts. Other organizations like Endangered Species International empower nearby human communities to restrict hunting and create economic alternatives to the widespread bushmeat trade. For this latter purpose, education is critical—people in the Congo often engage in destructive slash-and-burn agriculture simply because they have not learned of other approaches. The African Wildlife Foundation intervenes by funding sustainable schools in agricultural communities. Other efforts include the establishment of anti-poaching patrols through the DRC Army and, as always, scientific research to enhance our understanding of mangabey populations and the forces that threaten or improve their chances of survival.
Written by Eli Elster, February 2023