Red-bellied monkey, Cercopithecus erythrogaster
RED-BELLIED MONKEY
Cercopithecus erythrogaster
Geographic Distribution and Habitat
The red-bellied monkey, also known as the white-throated guenon, is found in the Niger Delta and throughout the southwest of Nigeria, into southern Benin and Togo. Their distribution is severely scattered due to forest fragmentation throughout the species’ range. Forest fragmentation results from urbanization and habitat destruction breaking expansive forest into small unconnected patches. While some species are able to maintain a foothold within these small fragments, it creates a divide in the population as a whole by making access to new mating opportunities and food sources difficult if not impossible.
Red-bellied monkeys can be found in forests that have not experienced habitat destruction (known as primary forests) as well as secondary forests that are recovering from previous disturbance. They are found in swamps, moist lowland forests, semi-deciduous forests, and forests that experience seasonal flooding (also known as seasonally inundated forests).
Two recognized sub-species: C. e. erythrogaster, which is also called the red-bellied monkey and is Critically Endangered, is found in the western-most portion of the species’ range in Nigeria, Benin and Togo while the Nigerian white-throated monkey, C. e. pococki (Endangered) is found only in the forested area of the Niger Delta. It is unclear how much the two subspecies may overlap in range, particularly due to the fragmentation of their habitat due to urbanization.
Size, Weight, and Lifespan
Like many primate species, the red-bellied monkey is sexually dimorphic, meaning one sex is larger in size than the other. As with many primates, male red-bellied monkeys are larger, with an average head-body length of 17.99 inches (457 mm), and weigh up to 9.92 pounds (4.5 kg). Females have a range of 14.96 inches–17.72 inches (380mm–450mm) head-body length and weigh around 5.29 pounds (2.4 kg). They have long tails to help them balance while walking along branches that are 22.83 inches–27.56 inches in length (580 mm–70mm).
The exact lifespan of red-bellied monkeys isn’t known for certain, but they likely can live into their 20s like many other guenons.
Appearance
A medium-sized monkey, red-bellied monkeys have a khaki-colored coat with limbs that are black on the outside, but white underneath contrasting the reddish fur on their underbelly (which is more of a grayish red in the pococki subspecies). The khaki color of their back fades into their long tails until reaching the black tip. As indicated by their alternate name (white-throated guenon), the fur on their throat is white, while the fur on the rest of their face is black except for their brown cheek patches. The fur on the top of their head is also black, with a triangle-shaped brown patch almost like a hat.
Diet
Red-bellied monkeys have similar dietary habits to most other guenon species and are known to primarily eat fruit while also enjoying the occasional insect and other plant materials such as leaves. Although juicy ripe fruits are preferred, when food becomes scarce in the dry season, unripe fruit will also be eaten (beggars can’t be choosers in the wild).
Like other guenons, red-bellied monkeys have cheek pouches for snacking on-the-go and molars specialized for munching on fruit and seeds.
Behavior and Lifestyle
Due to living mostly in hard-to-reach areas, not much is known about the specifics of their lifestyle. We do know that, like other guenons and many other primates, they walk quadrupedally (on all fours) and are arboreal (live mostly in the trees). They prefer the mid to lower forest canopy and are most active during the day (or rather, are diurnal).
The species’ scientific name erythrogaster comes from the Greek words for red (erythros) and belly (gastor).
Red-bellied monkeys live in groups of 5–30 individuals, however, all reports of larger groups were recorded in the 1980’s, with more recent studies documenting group sizes of 5-10 individuals. Groups typically have one male and multiple females, plus any sub-adults, juveniles, and infants. They sleep during the night in a tree near a source of water so they can start their hydration first thing in the morning (let this be your own reminder to drink water). After their morning drink, they move to the nearest fruiting tree for breakfast. During midday, the group will find a nice shaded area to nap in. Once rested, they return to their original sleeping tree or search for a new one near a more abundant fruiting tree if necessary. They are sometimes assisted in finding fruiting trees by hornbills by following their calls.
Red-bellied monkeys have been reported traveling with mona monkeys, and have also been observed with olive colobus and putty-nosed monkeys. Multi-species associations allow for better predator protection for all participating species. Not only do they have more eyes to rely on for spotting predators, but also have the ability to observe from different angles as different species occupy different levels of the canopy. Red-bellied monkeys have also been known to hybridize with Sclater’s guenons where their ranges overlap in the Niger Delta.
Communication in red-bellied monkeys has not been well studied, but they likely use the same forms of communication as other guenons. Facial expressions are a notable example for guenons. Common expressions include an eyebrow-raised stare directed to the recipient of an individual’s aggression, baring teeth when upset (which is the source of the name ‘guenon’ which comes from the French word for ‘fright’), and lip-smacking to show affection. This can be expanded to body motions, such as head bobbing to display aggression.
Vocalizations are also commonly used to locate other group members, warn others about potential threats, display dominance or submission, or interest in a potential mate.
Due to their skittish nature and preference for swampy habitats that are difficult for humans to access, not much is known about the specifics of red-bellied monkeys’ reproduction. We can make some good educated guesses, however, based on what we know about better studied guenon species. They likely have a 6-month gestation period, after which they give birth to a single offspring. Males would reach sexual maturity around 5 years of age, and females around 4 years.
While red-bellied monkey’s ecological role has not been specifically studied, like other fruit-eating monkeys we can assume they hold the important role of seed dispersers in their ecosystem. Seed dispersers help maintain the biodiversity of the forests they live in by spreading the seeds of the fruits they eat, either by carrying them off to feed on and dropping them or by consuming and passing them later on (in a convenient fertilizer packet). Scientists have shown that when primates are removed from a forest, the overall biodiversity of trees in that forest decreases, which underscores the importance of protecting threatened primate species such as the red-bellied monkey.
The red-bellied monkey is classified as Endangered by the International Union for Conservation of Nature (IUCN, 2016), appearing on the IUCN Red List of Threatened Species. Researchers estimate that the red-bellied monkeys’ population has decreased by 50% or more in the past 27 years (as of 2020) based on the amount of habitat loss experienced in their region. Habitat loss in the region has been the result of agricultural development and extraction of trees for artisanal purposes, and development of oil and gas pipelines. With the severe decline in populations of larger monkeys that are more often targeted for bushmeat, such as Niger Delta red colobus, white-thighed colobus, and red-capped mangabeys, more smaller monkeys including red-bellied monkeys are being targeted by poachers. While hunting of red-bellied monkeys has gone up in more recent years, their preference for swampy or flooded habitats has helped them stay out of reach of poachers.
Red-bellied monkeys are 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. They are also listed as Class A on the African Convention on the Conservation of Nature and Natural Resources, an agreement amongst the Assembly of the African Union to sustainably manage and conserve the natural resources of the African continent. They are present in several protected areas throughout their range, including the Togodo Faunal Reserve and the Okomu National Park.
Most conservation efforts for red-bellied monkeys focus on finding ways to retain the small amount of natural habitat left for them, while still supporting local people. Old teak plantations that have regenerated some undergrowth can provide a buffer zone between humanized areas and more protected forest ranges, and act as corridors between forest patches, balancing the need for suitable habitat for many species including the red-bellied monkey, and providing income for the local people.
- https://cites.org/eng/app/appendices.php
- https://www.iucnredlist.org/species/4217/17946182
- https://www.iucnredlist.org/species/40003/17984113
- https://www.iucnredlist.org/species/40004/17984075
- Ekaye, S. A., Dedekuma, O. N., & Oke, C. O. (2022). Preliminary study on some aspect of the ecology of Cercopithecus erythrogaster pococki (Grubb, Lernould and Oates, 2000) in Okomu National Park, Edo State, Nigeria. Journal of Research in Forestry, Wildlife and Environment, 14(1), 85-92.
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Written by Lina Rademacher, January 2025