GOLDEN-BELLIED MANGABEY

Cercocebus chrysogaster

Geographic Distribution and Habitat
Golden-bellied mangabeys are Old World monkeys endemic to the Democratic Republic of Congo in equatorial Central Africa. Home for most individuals is the sedimentary Congo Basin. Prior to being classified as its own species, the golden-bellied mangabey (Cercocebus chrysogaster) had been considered a subspecies of the agile mangabey (Cercocebus agilis).

The golden-bellied mangabey’s range is demarcated by the Congo River to the west, the Lomami River to the east, and the Lulonga River to the north. Because the species has been so little-studied, some of these geographic range limits are uncertain. Another field study suggests the Ngendo River as the species’s eastern border, the Lokolo River System as the northern border, and the Kwa-Kasai-Sankuru River as the southern border.

Commonly found in tropical rainforests, golden-bellied mangabeys prefer swampy habitats and thrive in wetlands at elevations up to 1,640 ft (500 m). Habitats include lowlands at or below sea level, usually no higher than 656 ft (200 m) that flood from November to March; riparian forests (situated along the banks of a river); and upland rainforests, 656 to 1,640 ft (200-500 m) in elevation. As altitudes increase, fewer swampy habitats exist so the population of golden-bellied mangabeys diminishes.

Golden-bellied mangabey geographic range. Map: IUCN, 2020

Size, Weight, and Lifespan
Golden-bellied mangabeys are large, long-limbed monkeys. Males are larger than females, an example of sexual dimorphism.

Head-to-body length for golden-bellied mangabeys is 15.75-31.50 in (40-80 cm), with an average length of 25.6 in (65 cm). The tail is longer than the body, adding another 17.7-39.4 in (45-100 cm), depending on an individual’s stage of maturity.

Males have a more robust build than the females of this species, weighing between 13 and 31 lb (6-14 kg). Females weigh between 9 and 18 lb (4-8 kg). At birth, golden-bellied mangabeys weigh a mere 1.10-1.32 lb (0.5-0.6 kg).

Lifespan in the wild is not documented. However, researchers conjecture that lifespan for the golden-bellied mangabey is likely similar to the collared mangabey (Cercocebus torquatus), also known as the red-capped mangabey, who lives an average of 25 to 27 years in the wild.

The recorded lifespan for captive golden-bellied mangabeys is between 20 to 35 years, with an average lifespan of 30 years.

Appearance
Golden-bellied mangabeys may be the most visually striking of all mangabey species. They get their name, of course, for the bright, luxuriant fur that covers their bellies—never mind that it’s actually orange, and not gold. Close enough. The remainder of their fur coat (known in science-speak as “pelage”) is dark brown to black and is accented by golden or orange specks. Creamy white fur fans out from the temples and from the chin of some individuals. Their muzzle is dark and hairless, and they have deep brown eyes. As babies, golden-bellied mangabeys resemble their parents; that is, they share the same coloration.

Besides their glorious, furry orange bellies, these monkeys are further distinguished by their white eyelids. It’s as if Mother Nature decided they needed some contrast to their dark face, so she powdered their upper eyelids with pale shadow.

Golden-bellied mangabeys are one of six mangabey species belonging to the exclusive white-eyelid mangabey club. The other distinguished members:

What Does It Mean?

Ecology:
The branch of biology that deals with the relations of organisms to one another and to their physical surroundings.

​Nonprehensile:
Incapable of grasping or gripping (opposite of prehensile: capable of grasping or gripping).

Omnivore:
An animal or person who eats food of both plant and animal origin.

Sexual dimorphism:
Distinct difference in size or appearance between the sexes of an animal in addition to difference between the reproductive organs themselves.

​Sympatric: 
Occurring or living in the same area; overlapping in distribution.

Visit the Glossary for more definitions

Diet
As omnivores, golden-bellied mangabeys are opportunistic eaters; they eat pretty much everything their rainforest environment offers: insects, spiders, fruits, nuts, seeds, leaves, grains, and fruit nectars. Seasonal availability determines which food items are on their buffet table, or rather, tree branch.

Strong jaws and teeth enable these monkeys to bite through shelled nuts and tough-skinned fruits. And the cheek pouches they are fitted with allow them to store food for a later snack.

Behavior and Lifestyle
Few studies have been published about this species. To fill in the gaps about behavior and lifestyle, scientists base their findings on studies of captive golden-bellied mangabeys. They also look to similar species for possible clues.

Daily Life and Group Dynamics 
Golden-bellied mangabeys live in social family groups, typically led by an alpha male, of about 15 members; however, groups as large as 100 members or more have been reported.

The species is crepuscular, a fancy way of saying that golden-bellied mangabeys are most active during twilight hours, just before sunrise, when they have a better chance of finding food sources before other animals get to them. Most of their daily food intake is consumed in the morning hours, perhaps giving credence to the adage that breakfast is the most important meal of the day.

They are a nomadic species, covering an area of 10,764 sq ft (1,000 sq m) per day while traveling as a group to forage. As they move quadrupedally (on all fours) through the forest canopy, their long, nonprehensile tails help them to balance. Although golden-bellied mangabeys are mostly arboreal (tree dwelling), they also forage on the ground.

Home range for golden-bellied mangabeys is unknown, but home range of one similar species, the agile mangabey, is 489 ac (198 ha); yet the highly endangered Tana River mangabey has a home range of only 37 ac (15 ha). (This disparity highlights the potential shortcomings in looking to similar species for clues, rather than conducting more earnest studies of a specific species, in this case the golden-bellied mangabey.)

All adults of a group protect their young. Females are more apt to act aggressively should a predator threaten their offspring. Besides humans, golden-bellied mangabeys may also be preyed on by large snakes, birds of prey, and large wild cats.

Golden-bellied mangabeys do their best to avoid outside mangabey groups in their travels, and they rarely engage with other species. Should they encounter an outside mangabey group or a perceived predator, members at the front of a foraging party emit alarm calls to warn others to retreat to safety.

Fun Facts

The Nkundo people (also known as Mongo), who share habitat with golden-bellied mangabeys, refer to the species as “Linku” in their native Lonkundo language.

Communication
Golden-bellied mangabeys communicate primarily through vocalizations; these vocalizations, or calls, include low grunts or barks and high-pitched shrieks. In addition to alarm calls, loud warning calls convey a sense of urgency or imminent danger; these calls are the species’ only defense against predation. Males are more likely to emit warning and alarm calls, but females do so when necessary. Specialized sacs in the throats of golden-bellied mangabeys allow their calls to be heard up to a distance of 0.62 mi (1 km). Males are significantly louder than females.

Other calls announce location, and still other calls convey non-emergency messages.

Olfactory communication plays a role in daily life. Golden-bellied mangabeys possess a strong sense of smell that allows them to “sniff out” information in their environment.

It is unknown whether golden-bellied mangabeys possess color vision; however, they rely on their eyesight to spot other members of their group, as well as predators, in their dense rainforest environment.

They rely on tactile sensations to feel, climb, and grab their way through dense trees, and to collect food.

Reproduction and Family
Female golden-bellied mangabeys reach sexual maturity (capable of conceiving and baring young) at 4 to 5 years of age. Males are “late bloomers,” reaching sexual maturity (capable of siring offspring) at 5 to 7 years of age.

The species is polygynandrous, a fancy way of saying that that both males and females have multiple mating partners during a breeding season. As she ovulates, a female’s buttocks swell, attracting the attention of sexually mature males. Skirmishes may ensue between male members of a female’s group, who vie for the opportunity to mate with her.

Golden-bellied mangabeys breed once a year, from March through August. After a gestation period of about 6 months, a female gives birth to a single offspring. Babies have surprising strength from birth and are able to grip onto the back of their mothers for safety. Infants are considered weaned at 7 to 10 months old; however, offspring are not fully independent until they are between 2 and 6 years old, with 4 to 5 years being the average age range.

Little more is known about child-rearing in this species. For additional clues, researchers look to two similar species: the Tana River mangabey and the collared mangabey. Female Tana River mangabeys form strong bonds with their mothers (however, researchers have not been able to attribute this behavior to golden-bellied mangabeys in the wild). Collared mangabey infants instinctively cling to their mothers immediately after they are born (similar behavior has been observed in golden-bellied mangabeys).

Ecological Role
Golden-bellied mangabeys may not play as large a role in regenerating their habitat as strictly frugivorous (fruit-eating) primates. Regardless, fruits comprise a portion of their diet and golden-bellied mangabeys should be credited with helping to encourage new rainforest growth by distributing the seeds of these fruits via their feces.

Of course, it’s self-centered and almost farcical for humans to determine the role, or purpose, of other sentient beings. Golden-bellied mangabeys have their own purpose in the world we share with them.

Conservation Status and Threats
The golden-bellied mangabey is listed as Endangered by the International Union for Conservation of Nature, appearing on the IUCN Red List of Threatened Species (IUCN, 2020). All known populations are currently in decline. Threats include uncontrolled commercial bushmeat hunting that targets the species, as well as habitat loss and degradation by logging.

High numbers of golden-bellied mangabeys are killed for the commercial bushmeat trade across their range. This has led to ongoing dramatic population declines. The species appears to be highly vulnerable to hunting.

In some regions within its range numerous animals were systematically hunted down in a confined area.

Earlier debate about the golden-bellied mangabey’s ranking as a species vs. a subspecies may have contributed to its lack of protections—and to a dearth of research into the species ecology and conservation.

Feeble conservation has allowed a siege upon golden-bellied mangabeys by their deadliest predator: humans. Humans hunt and kill golden-bellied mangabeys for the primates’ flesh, known as bushmeat. And they target the species for the illegal pet trade, killing mothers and kidnapping their babies. Ill-gotten golden-bellied mangabey babies also end up in zoos.

Regarded by locals as an agricultural pest, golden-bellied mangabeys face further persecution for their forays into villages. Because they typically forage in groups of 15 individuals, they are easy targets for hunters.

Even those individuals living within the borders of Salonga National Park are not safe; Africa’s largest tropical rainforest reserve is supposed to be a refuge for these golden-bellied mangabeys, who reside in the park’s southern sector—but it is an unlikely hunting ground. Using canoes, hunters maneuver through deep waters of flooded rainforest to access and kill their golden-mangabey prey. Other wildlife species residing (and at risk) in the park including bonobos; forest elephants; Dryas monkeys (Cercopithecus dryas), also known as Salonga monkeys; and Thollon’s red colobus (Procolobus tholloni), also known as the Tshuapa red colobus.

Habitat loss poses an additional threat to the species’s survival; large tracts of forest have been razed to supply the logging industry. Already, golden-bellied mangabeys have a more restricted distribution range than many other sympatric primate species such as the black-crested mangabey (Lophocebus aterrimus) and the Angolan colobus (Colobus angolensis). Increasing loss of habitat further jeopardizes the golden-bellied mangabey’s future in our world.

Conservation Efforts
The golden-bellied 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. (All nonhuman primates not listed in CITES Appendix I are listed in Appendix II.) Other than the species’s secondary listing in CITES, no specific conservation measures exist for golden-bellied mangabeys. They are conspicuously missing from the list of protected species under Democratic Republic of Congo national law. Some conservationists would like to change that.

Researcher-advocates for the golden-bellied mangabey assert that the species’s IUCN ranking should be upgraded to Endangered; they further assert that the Democratic Republic of the Congo recognize the golden-bellied mangabey as one of that country’s threatened endemic species. These conservationists also call for additional field research to fully determine the species population and distribution, define its ecology, and evaluate threats to its survival.

References:
http://www.iucnredlist.org/details/4207/0
https://en.wikipedia.org/wiki/White-eyelid_mangabey
http://cornwallcameratrapping.blogspot.com/2014/07/only-know-footage-of-wild-golden/
https://en.wikipedia.org/wiki/Lulonga_River
https://en.wikipedia.org/wiki/List_of_rivers_of_the_Democratic_Republic_of_the_Congo
https://en.wikipedia.org/wiki/Mongo_people

Written by Kathleen Downey, October 2018. Conservation status updated July 2020.