Rusty-mantled Mangabey
Lophocebus albigena osmani
No photos of the rusty-mantled mangabey are available. This is the gray-cheeked mangabey photos (Lophocebus albigena) of which the rusty-mantled mangabey is a subspecies.
Geographic Distribution and Habitat
The rusty-mantled mangabey, also called the Osman Hill’s mangabey, occupies a small range in Western Africa from the Cross River in southeastern Nigeria to the Batouri district of southeastern Cameroon. The rusty-mantled mangabey is a subspecies of the gray-cheeked mangabey (Lophocebus albigena) in the crested mangabey group. Highly arboreal, they live in the medium-to-high-altitude canopy and emergent layers of tropical rainforests at 1,968 feet (600 m) and higher, in flooded forests, and in swamp forests. They rarely descend to the ground and are rarely seen in secondary forests or savanna habitats.
The rusty-mantled mangabey, also called the Osman Hill’s mangabey, occupies a small range in Western Africa from the Cross River in southeastern Nigeria to the Batouri district of southeastern Cameroon. The rusty-mantled mangabey is a subspecies of the gray-cheeked mangabey (Lophocebus albigena) in the crested mangabey group. Highly arboreal, they live in the medium-to-high-altitude canopy and emergent layers of tropical rainforests at 1,968 feet (600 m) and higher, in flooded forests, and in swamp forests. They rarely descend to the ground and are rarely seen in secondary forests or savanna habitats.
Rusty-mantled mangabey geographic range. Map: IUCN, 2019 (click to enlarge)
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Size, Weight, and Lifespan
The head-to-body length of the rusty-mantled mangabey measures from 18 to 36 inches (45.72–91.44 cm). Females are usually smaller and lankier than males. Both males and females have long tails, usually measuring longer than their bodies and measuring up to 39 inches (99 cm). Males are heavier than females at between 13 and 24 pounds (6–11 kg); females weigh between 8 and 15 pounds (3.6–7 kg). The lifespan of rusty-mantled mangabeys is not well documented; however, it is assumed that they have a similar lifespan to the closely related gray-cheeked mangabey. In the wild the average lifespan is 20–22 years old and in captivity they can live up to 32 years. Appearance
Rusty-mantled mangabeys are medium-to-large-sized monkeys. Both males and females are similar in fur color and markings; however, they are sexually dimorphic in size. They have long, loose, dark blackish, brownish fur. There is usually a black patch on the nape (back) of their neck, and the withers (ridge between the shoulder blades) and the underside is yellow-gray. Their name comes from the reddish tinged mane of longer hairs over their shoulders, which is more noticeable in males. Although not always present, sometimes they have a tuft on the crown and a smaller tuft above the eyes. Unlike the gray-cheeked mangabey and the Johnston’s mangabey, the rusty-mantled mangabey’s hair above the brows never form “horns.” The crown hair is much neater than in the gray-cheeked and Johnston’s mangabey. In addition, their cheeks are much more pale than their bodies. Rusty-mantled mangabeys have bare skin on the palms of the hands and soles of the feet. These typically start out as a pinkish color in infants and darken as they age to black. At about nine months of age their palms and soles are black. They have long limbs and tails, which are usually held arched over their back and provide balance when traveling through the forest. Their tails, although not prehensile, are strong enough to hook onto tree branches when needed. Males and females both have two ischial callosities (thick callus-like skin on their buttocks), which form “C” shapes. When a female is ready to breed, these callosities turn pink and swell. Rusty-mantled mangabeys have powerful jaws, long molars, and large incisors. They also have cheek pouches that allow them to store food for later consumption. |
What Does It Mean?Gestation Period:
The time of pregnancy from conception until birth. Hierarchy: A system of organization in members of a group who are ranked one above the other according to status or authority. Interbirth interval: Refers to the period of time between successive births of an individual female. Ischial callosities: A thickened piece of skin found on the buttocks of animals. Sexually dimorphic: When males and females have different characteristics (size, color, etc.) other than their reproductive organs. |
No photos of the rusty-mantled mangabey are available. This is the gray-cheeked mangabey photos (Lophocebus albigena) of which the rusty-mantled mangabey is a subspecies.
Diet
The diet of rusty-mantled mangabeys is dominated by fruits and seeds, which are considered the most important foods in their diet. They prefer to feed and forage high in the forest canopy. There are seasonal fluctuations of fruit availability and they fall back on foods like flowers, leaves, bark, nuts, and invertebrates.
When food is scarce—specifically fruit—rusty-mantled mangabeys spend more time foraging. Food scarcity causes them to intermittently descend to the ground and spend more time in swampy areas. When fruits are available, their foraging time decreases and they tend to stay much higher in the trees.
Their teeth are specialized for processing and cracking open hard foods or shells. Eating such hard foods consistently wears down their teeth and can ultimately lead to an early death.
The diet of rusty-mantled mangabeys is dominated by fruits and seeds, which are considered the most important foods in their diet. They prefer to feed and forage high in the forest canopy. There are seasonal fluctuations of fruit availability and they fall back on foods like flowers, leaves, bark, nuts, and invertebrates.
When food is scarce—specifically fruit—rusty-mantled mangabeys spend more time foraging. Food scarcity causes them to intermittently descend to the ground and spend more time in swampy areas. When fruits are available, their foraging time decreases and they tend to stay much higher in the trees.
Their teeth are specialized for processing and cracking open hard foods or shells. Eating such hard foods consistently wears down their teeth and can ultimately lead to an early death.
Behavior and Lifestyle
Rusty-mantled mangabeys are diurnal (active during the day) and travel quadrupedally through the forest. They travel most of the day and rest between feeding. Sometimes they descend to the ground to feed or raid cultivated fields for maize and sweet potatoes.
Rusty-mantled mangabeys are diurnal (active during the day) and travel quadrupedally through the forest. They travel most of the day and rest between feeding. Sometimes they descend to the ground to feed or raid cultivated fields for maize and sweet potatoes.
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Daily Life and Group Dynamics
Home range sizes vary widely both within and between crested mangabey species. The home range size of the rusty-mantled mangabey is not well documented. It is suggested that their ranges could be similar to other crested mangabey species like the black crested mangabey from Uganda, whose range spans from .05 to 1.6 square miles (0.13–4.1 square km) or the gray-cheeked mangabey from the Democratic Republic of Congo, whose ranges span .23 square miles (.60 square km). Home ranges of neighboring groups tend to overlap. Group size in the rusty-mantled mangabey is smaller, at 5 to 20 individuals, than those in the white eyelid mangabey group, like sooty-mangabeys whose troop sizes may include as many as 100 individuals. Rusty-mantled mangabeys are social primates and live in multi-male, multi-female groups, with one to five males. The larger the group, the more males there are. Groups are fluid and sometimes mix, though this can lead to increased aggression among adults. Both males and females form a hierarchy, where all other individuals are ranked under the alpha male and female. Higher ranking individuals get first dibs on resources like food and forage in the center of the group where they don’t have to worry about competition or surrounding predators. Lower ranked group members stay on the periphery and tend to consume less food than the higher ranked members. Higher ranking males reap the benefit of better breeding opportunities; however, lower-ranking males sneakily copulate with females when opportunities arise. Young rusty-mantled mangabeys enjoy playing with one another high in the canopy. Play includes swinging and jumping from tree to tree. Sometimes adults participate in play with their young. |
Fun FactsSometimes rusty-mantled mangabeys locate fruiting trees by following the calls of frugivorous birds such as hornbills. The rusty-mantled mangabeys alternative name, Osman Hill’s mangabey, was named after William Charles Osman Hill, a primatologist, anthropologist, and anatomist. |
Communication
Mangabeys communicate with each other in some interesting ways. It can be difficult for them to see one another in the dense canopy, so sound is very important. Mangabeys have a special throat sac that allows them to produce loud calls. In males, the sac is larger and facilitates shrieking alarm calls to warn others when there is a threat. A male mangabey emits barking calls and grunts to let other troops know where he is so they don’t intrude. In addition, mangabeys make a “whoop-gobble” call—the whoop sound gets the attention of the other mangabeys in the area and the gobble tells everyone who and where he is. Whoop-gobble calls can be heard up to over half a mile (1 km) away.
Females join in on the loud calls, but not the whoop-gobble calls. Females emit progression calls, which consist of nasal grunts. These calls have a short range and are emitted by group members to no specific receiver.
Visual communication is used when group members come in contact with one another. Staring is a threat. Staring with an open mouth but with teeth covered is also a threat, and is often accompanied by head-bobbing. Pouting is a visual display used by females to communicate sexual receptivity. This occurs when the lips are protruded forward.
Mangabeys also use tactile communication. Tail-twining communicates strong social bonds between two individuals while they sit on a tree branch.
Mangabeys communicate with each other in some interesting ways. It can be difficult for them to see one another in the dense canopy, so sound is very important. Mangabeys have a special throat sac that allows them to produce loud calls. In males, the sac is larger and facilitates shrieking alarm calls to warn others when there is a threat. A male mangabey emits barking calls and grunts to let other troops know where he is so they don’t intrude. In addition, mangabeys make a “whoop-gobble” call—the whoop sound gets the attention of the other mangabeys in the area and the gobble tells everyone who and where he is. Whoop-gobble calls can be heard up to over half a mile (1 km) away.
Females join in on the loud calls, but not the whoop-gobble calls. Females emit progression calls, which consist of nasal grunts. These calls have a short range and are emitted by group members to no specific receiver.
Visual communication is used when group members come in contact with one another. Staring is a threat. Staring with an open mouth but with teeth covered is also a threat, and is often accompanied by head-bobbing. Pouting is a visual display used by females to communicate sexual receptivity. This occurs when the lips are protruded forward.
Mangabeys also use tactile communication. Tail-twining communicates strong social bonds between two individuals while they sit on a tree branch.
Reproduction and Family
Mating season is May through September, though breeding can occur at any time during the year. Females typically give birth to one infant after 6 months of gestation. Mothers give birth once about every 13 to 16 months. A longer interval between births is beneficial since it allows the mother more time caring for her young. An infant is carried on their mother’s belly then, after a few months, are carried on her back. The mother provides most of the care for the infant for the first 7–10 months after birth, such as feeding/nursing, grooming, and protecting. At around 10–12 months, other females, or “aunts,” start to help feed and groom the infant. Siblings also help out with grooming. Males occasionally carry their infants for protection.
Males reach maturity at about 4–5 years of age, and females around 3.5–4 years of age. After maturity, males leave their natal group and females usually stay.
Mating season is May through September, though breeding can occur at any time during the year. Females typically give birth to one infant after 6 months of gestation. Mothers give birth once about every 13 to 16 months. A longer interval between births is beneficial since it allows the mother more time caring for her young. An infant is carried on their mother’s belly then, after a few months, are carried on her back. The mother provides most of the care for the infant for the first 7–10 months after birth, such as feeding/nursing, grooming, and protecting. At around 10–12 months, other females, or “aunts,” start to help feed and groom the infant. Siblings also help out with grooming. Males occasionally carry their infants for protection.
Males reach maturity at about 4–5 years of age, and females around 3.5–4 years of age. After maturity, males leave their natal group and females usually stay.
Ecological Role
Consuming a high amount of fruits and seeds help rusty-mantled mangabeys act as seed dispersers throughout their range. They can also be pollinators. When eating nectar from flowers, pollen from the flowers attaches to their fur. When foraging from tree to tree, the pollen drops from their fur.
Consuming a high amount of fruits and seeds help rusty-mantled mangabeys act as seed dispersers throughout their range. They can also be pollinators. When eating nectar from flowers, pollen from the flowers attaches to their fur. When foraging from tree to tree, the pollen drops from their fur.
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Conservation Status and Threats
Unfortunately there is insufficient information for a proper assessment of the rusty-mantled mangabey. Thus, the rusty-mantled mangabey is listed as Data Deficient by the International Union for Conservation of Nature (IUCN, 2020). The main threats to the rusty-mantled mangabey are hunting for their meat and clearance of forest for agriculture and logging, as well as railroads and roads. Although rusty-mantled mangabeys can adapt to secondary forests, they highly depend on primary forests and may even be less adaptable to secondary forest than other primates. Predators of rusty-mantled mangabeys are crowned hawk-eagles, leopards, humans, and occasionally chimpanzees. |
Conservation Efforts
In Cameroon, rusty-mantled mangabeys occur in Mbam et Djerem National Park, the Douala-Edéa Faunal Reserve, and the Dja Biosphere Reserve where they are protected. A very small population may also occur in Nigeria’s Gashaka-Gumti National Park.
Rusty-mantled mangabeys are listed under the Convention on International Trade in Endangered Species (CITES) Appendix II and as Class B under the African Convention on the Conservation of Nature and Natural Resources.
Though there is little information about the rusty-mantled mangabey, it is likely that their populations are declining due to the ongoing hunting pressure and habitat loss. More information on human impacts to the rusty-mantled mangabey is needed to assess proper conservation methods to sustain both the species and their surrounding habitats.
In Cameroon, rusty-mantled mangabeys occur in Mbam et Djerem National Park, the Douala-Edéa Faunal Reserve, and the Dja Biosphere Reserve where they are protected. A very small population may also occur in Nigeria’s Gashaka-Gumti National Park.
Rusty-mantled mangabeys are listed under the Convention on International Trade in Endangered Species (CITES) Appendix II and as Class B under the African Convention on the Conservation of Nature and Natural Resources.
Though there is little information about the rusty-mantled mangabey, it is likely that their populations are declining due to the ongoing hunting pressure and habitat loss. More information on human impacts to the rusty-mantled mangabey is needed to assess proper conservation methods to sustain both the species and their surrounding habitats.
References:
- https://www.iucnredlist.org/species/92248950/176624827
- file:///C:/Users/cover/Downloads/052.022.0112%20(1).pdf
- http://www.newworldencyclopedia.org/entry/Mangabey
- https://www.eaza.net/assets/Uploads/CCC/BPG-2019/EAZA-BPG-Mangabey-2.pdf
- Mcgraw, SC. 2017. Mangabeys (Cercocebus and Lophocebus). The International Encyclopedia of Primatology. 1-3.
- Groves, CP. 2007. The Endemic Uganda Mangabey, Lophocebus ugandae,and Other Members of the Albigena-Group (Lophocebus). Primate Conservation. 22(1): 123-128.
Written by Tara Covert, January 2021
