Geographic Distribution and Habitat
The sooty mangabey, also known as the white-crowned or white-collared mangabey, is a mostly terrestrial Old World monkey. Endemic to Côte d’Ivoire, Guinea, Guinea-Bissau, Liberia, Senegal, and Sierra Leone, they have been eradicated from many regions within their range. They are considered to be mostly extinct in Senegal, Guinea-Bissau, and parts of Guinea.
West Africa’s tropical high forest is the species’ primary habitat, but sooty mangabeys also live in primary, secondary, flooded, dry, gallery, and mangrove forests where these foraging monkeys can be found walking along the forest floor gathering fruits and seeds. They have also been known to venture onto farmland in Ghana. Although sooty mangabeys spend the majority of their time on the ground, they will climb trees to avoid or escape predators.
Size, Weight, and Lifespan
Sooty mangabeys are medium-sized monkeys and sexually dimorphic, with males measuring 18 to 26 in (47 to 67 cm) in length and weighing about 5 to 26 lb (7 to 12 kg), and females being slightly smaller, measuring 17 to 24 in (45 to 60 cm) and weighing 10 to 15 lb (4.5 to 7 kg). A male is about as heavy as a dachshund dog, and a female sooty mangabey weighs about as much as the average house cat.
Male sooty mangabeys have longer canine teeth than females. Both sexes have long tails,16 to 31 in (40 to 60 cm), that help them with balance when running, playing, or foraging. As is typical of Old World monkeys, sooty mangabeys’ tails are not prehensile; that is, their tails are incapable of grasping objects.
Sooty mangabeys live to be 18 years old in the wild.
Imagine the soot that covers someone after cleaning a chimney or the ashes left in your fire pit when you go camping; this is the color of the sooty mangabey. Sooty mangabeys are cloaked in dark, ash-gray fur; the fur on their underside is a lighter, smoky-gray color. Their hands, feet, and ears are dark gray or black.
The skin on the sooty mangabey’s hairless face is either a salmon color or a mottled gray, and their long muzzle is dark. Light-colored whiskers extend from the monkey’s cheeks, adding contrast to the dark fur framing the face. Bright, white eyelids suggest an expression of surprise. Sooty mangabeys make use of their bright eyelids, raising and lowering them, to communicate with others.
Sooty mangabeys eat both plants and animals. Fruits and seeds comprise the greater part of their diet, with insects comprising a much smaller portion. Grass, fungi, small invertebrates, and dinner delicacies like tadpoles plucked from shallow ponds round out their menu.
Their large cheek pouches allow them to store food for snacking on later. Strong, powerful jaws and large incisor teeth enable sooty mangabeys to eat hard objects that many other animals cannot eat, including nuts with hard kernels and palm nuts, both the flesh and kernels. This natural adaptation helps ensure the species’ viability.
Due to the size difference in their incisor teeth, male and female sooty mangabeys have different dietary preferences, or proclivities. With his larger incisor teeth, the male sooty mangabey eats more hard nuts, seeds, and crunchy invertebrates. The female, with her daintier incisor teeth, prefers to eat softer seeds and fruits.
Behavior and Lifestyle
Sooty mangabeys are diurnal, meaning that they are active during daylight hours. Most of their day is spent on the ground foraging for food. They cover their territory by moving quadrupedally, that is, on all fours. Their time spent in trees is limited and is restricted to the forest understory, where they climb or leap. Sooty mangabeys spend a large amount of their day resting and interacting socially with members of their group.
Sooty mangabeys remember the locations of fallen fruit and can determine whether or not a tree is producing fruit.
Sooty mangabey are incredibly effective at spotting predators.
Mothers have been observed grooming their infants with a stone, but researchers are unsure why. This may be an example of tool use.
Group size can range from 15 to more than 100 individuals, typically with more males than females. These monkeys are always within 3 ft (1 m) of another group member, and they huddle even closer during severe weather.
The social structure of a group is dominated by a male hierarchy, with an alpha male at the top, followed by the other males in the group, followed by an alpha female, followed by the other females in the group. An alpha male may attempt to copulate with all the females of a group. Males with higher status, or ranking, mate more frequently. During copulation, males can be aggressive and sometimes slap the females.
Males might leave their group for months at a time to interact with other females in nearby groups. These wandering males have been known to commit infanticide; they deliberately kill the infants of an established group with the goal of taking over the group and siring their own offspring. Females remain with their natal (birth) group. Despite male aggression toward females and infants, sooty mangabeys display some of the lowest rates of aggression and combative behavior among primates.
Sooty mangabeys have been observed in mixed groups with other primate species. Researchers believe that these mixed groups offer added protection against arboreal and terrestrial predators. Diana monkeys (Cercopithecus diana) and red colobus monkeys (Piliocolobus badius), who are mostly arboreal (tree-dwelling), will risk feeding closer to the ground, knowing that the sooty mangabey’s loud alarm calls will alert them to potential danger.
Sooty mangabeys are vocal monkeys. Grunts, twitters, screams, growls, and alarm calls are used to communicate. Grunts are more often elicited by males; these low-frequency vocalizations typically accompany foraging activities. Twitters, which can be either soft- or sharp-sounding and have up to 23 syllables, are used by adult females or by juveniles who are interacting socially. Screams are more common to adult females, usually sounded in response to male aggression. Growls accompany aggressive behavior.
Alarm calls warn group members of potential predator threats. They use unique alarm calls to identify each predator type. For example, one call identifies a leopard, while another identifies a Gaboon viper, and another still identifies a threat from above, like an eagle. Different calls enable the group group members to determine how best to seek out safety either above or below the predator’s location.A female sooty mangabey is able to recognize an alarm call elicited from a member of her own group, so she can potentially protect her young from an attack by a wandering male from an outside group.
Sooty mangabeys use facial expressions to communicate. When raising their bright white eyelids, they are threatening another monkey. Other expressions—such as when these monkeys “grin” and stick out their tongues—are less understood by researchers.
Sooty mangabeys have a promiscuous breeding system: both males and females have multiple partners. Mating season begins in May and ends in September in the wild, but births can occur year-round.
Males become sexually active at about 1 year old, but they are not considered sexually mature (capable of siring offspring) until 4 years old. They copulate more often as adolescents, prior to achieving sexual maturity.
Females are considered sexually mature (capable of conceiving) at about 2.5 to 3 years old. They present themselves to the males to initiate copulation. Unlike other promiscuous breeding systems, female sooty mangabeys are not aggressive toward one another. A single infant is born after a gestation period of 167 days. The time between births is typically 14 to 16 months.
Once an infant is born, the mother carries him or her on her ventral side (stomach); after a few months, she carries the baby on her back. From 2 to 7 months, the mother is the child’s primary caregiver. However, if a threat presents itself, males might carry the youngster to offer greater protection. Once the child is older, aunts and siblings help groom the youngster.
Should a child die within the first 6 months of its life, the mother immediately goes back into estrus. This condition gets the attention not only of dominant males within her group, but also from wandering males. Older and higher-ranking males of the female’s group do their best to protect her and the group’s surviving infants from wandering males, but they are not always successful.
Because of their tendency to take one bite of a fruit before tossing it to the ground, sooty mangabeys might mistakenly be thought of as wasteful. But they are actually helping to maintain the health of their ecosystem. Their discarded fruit, along with the seeds distributed through their feces, are essential in helping to regenerate plant life throughout the sooty mangabey’s habitat.
The sooty mangabey is classified as Vulnerable by the International Union on Conservation of Nature (IUCN, 2019), appearing on the IUCN’s Red List of Threatened Species. Their population is estimated to have declined by at least 30% over the past 27 years (equivalent to three generations). The causes of the decline are intensive hunting across its range, combined with habitat loss and degradation resulting from the expansion of commercial and subsistence agriculture. The declining population trend is predicted to continue at the same or an accelerated rate.
Forest habitat is being lost through farming, logging, firewood harvesting and mining, all of which are being accentuated by a high rate of human population growth. The species is locally hunted for meat, and this is an increasingly important threat with ongoing forest fragmentation, because animals can be located more easily by hunters in small forest fragments.
Sooty mangabeys are natural reservoir hosts of Simian Immunodeficiency Virus (SIV). Despite a high prevalence in the wild population, the virus has no detectable impact on the survival or health of this host species. Sooty mangabeys do not develop AIDS, despite high levels of SIV infection, because of several genetically-based mechanisms that enhance immune function. They can, however, contract leprosy. In addition, Type 2 diabetes is more common in mangabeys than in other nonhuman primate species. The bushmeat trade, the practice of keeping monkeys as pets, and the growing number of people living near wild sooty mangabeys significantly increase the risk of transmission of multiple zoonotic diseases, infectious diseases caused by a pathogen (an infectious agent, such as a bacterium, virus, parasite or prion) that has jumped from a non-human animal to a human.
The sooty mangabey is listed on Appendix II of CITES and on Class B of the African Convention on the Conservation of Nature and Natural Resources.
They occur in a number of protected areas including Taï National Park (Côte d’Ivoire), Sapo National Park, Grebo-Krahn National Park and Gola National Park (Liberia), Tiwai Island Wildlife Sanctuary, Gola Forest National Park and Loma Mountains National Park (Sierra Leone), and the Cantanhez Forest National Park (Guinea-Bissau).
Taï National Park, one of the last primary forests in West Africa, is home to a wild study site of the sooty mangabey.
The species is also conserved in Gbepleu sacred grove in western Côte d’Ivoire near the town of Man.
Written by Laura Fern, December 2017. Conservation status updated July 2020.