DE BRAZZA’S MONKEY
Geographic Distribution and Habitat
The De Brazza’s monkey (Cercopithecus neglectus), also known as the De Brazza’s guenon, the Ayatollah monkey, or the swamp monkey, is a shy and watchful African monkey. Named for Italian-French naturalist and explorer Pierre Savorgnan de Brazza, the species earned its scientific designation, neglectus, from its ability to hide and successfully avoid discovery. Despite their evasiveness, the De Brazza’s monkey inhabits a vast stretch of Central Africa, including Angola, Cameroon, the Central African Republic, the Democratic Republic of Congo, Congo, Equatorial Guinea, Ethiopia, Gabon, Kenya, South Sudan, and Uganda. Though one may not be able to see them easily, any area near a river or swamp covered with dense forest or vegetation may very well host this eclectic group.
Size, Weight, and Lifespan
The species has significant sexual dimorphism in size. Males typically reach 25 inches (63.5 cm) and weigh roughly 15–17 (6.8–7.7 kg). Females are closer to 16 inches (40.6 cm), with an average weight of 8 pounds (3.6 kg). Their tails are longer than their combined head and body length.
The average lifespan is 22 years, although it is reported that some have lived to be up to 30 years old in captivity.
Based on their unique facial features, one might view De Brazza’s monkeys as wise and even mystical. An orange crest rests above watchful, apricot-colored eyes, framed by a black crown and a striking white beard. Their bodies are covered in a speckled gray coat, contrasted by black limbs and a signature white streak along their hindquarters. Like all Afro-Eurasian monkeys, their tail is not prehensile, but it affords balance while traveling through trees. Adult males have a blue scrotum that may act as a distinguishing feature for attracting females.
Babies are born with golden pelage and soft, pink faces and hands. Their spotted fur, dark limbs, and white markings do not appear until they have matured, transitioning into juveniles between the age of 6–12 weeks.
Among guenons, the De Brazza’s monkey is the largest species. Powerful legs allow them to run on all fours, gather food with their hands, and store them in their large cheek pouches. Cheek pouches are internal pockets on the sides of the head, between the jaw and the cheek, that allow them to store food and carry it away to enjoy in a safe and quiet setting. These pouches share the same capacity as their stomach, which allows them to be highly effective gatherers. When stressed, threatened, or asserting dominance, males yawn to show off their sharp canine teeth.
As omnivores, De Brazza’s monkeys enjoy a diversified palate provided by their rainforest habitat. Sharp teeth allow them to pierce through ripe fruits, seeds, herbaceous plants, mushrooms, beetles, termites, small reptiles, and flowers. They typically eat twice a day during the early morning and late evening. They forage within a condensed 0.3-mile (.48-km) territory. Given the choice, De Brazza’s monkeys prefer to satisfy their sweet tooth and opt for fruits and seeds above all else; they are considered frugivorous (fruit-eaters) 75% of the time.
Behavior and Lifestyle
De Brazza’s monkeys are surveyors of the forest, utilizing arboreal, terrestrial, and aquatic movements as needed. They live in the lower canopy of the forest, hidden away in dense vegetation. They descend to forage the forest floors twice a day (morning and evening).
Gifted swimmers, they live within a mile (1.6 km) of rivers and swamps. They are highly territorial towards other primates and sometimes even those of the same species, but when unprovoked, often communicate non-verbally, using eye contact, facial expression, and body language.
When frightened, they opt to freeze, hide, and wait for the danger to pass. However, if pressed, these guenons will make booming vocalizations and violently shake branches if a predator or stranger comes too close.
In captivity, De Brazza’s monkeys roam more confidently in open spaces and are less hesitant around other species.
When threatened, De Brazza’s monkeys freeze or curl into a ball. They can remain motionless for up to 8 hours.
The second half of its scientific name, Cercopithecus neglectus, is a Latin word which means “to be neglected, or overlooked.” This is based on the De Brazza monkey’s skill in remaining hidden from humans and predators.
To scare away predators, they have been known to shake branches and make booming vocalizations.
De Brazza’s monkeys swim! Though they prefer the safety of the canopy, the monkeys can be found submersed in bodies of water, giving them the nickname “swamp monkeys.”
De Brazza’s monkeys live in group sizes of 4–10 members, called troops. Some factions have been known to reach a whopping 30–35 members.
Females remain in their natal groups, meaning they remain with the troop they were born into for all their lives. Males are philopatric, leaving their natal group upon maturation to establish their own troop. This is to ensure genetic diversity and prevent inbreeding.
Most groups consist of one male and several females. However, there are factions in Gabon and Cameroon, as well as a few other isolated instances, where monogamous pairs have been reported.
Like other guenons, De Brazza’s monkeys emit calls like grunting or cackling. They have also been known to bark warnings in the presence of threats. Known for their deep “booming” call, these swamp monkeys can project calls that travel several hundred feet or meters. In captivity, up to ten different call types have been documented.
However, what makes this species truly unique is their display of non-verbal cues, relying heavily upon body language. Staring, staring with mouths open, bobbing of the head, head shaking, yawning, and “fear grimaces” have all been known to act as forms of intimidation. This silent communication may coincide with their preference to remain hidden and to communicate without being detected.
De Brazza’s monkeys reach sexual maturity between the ages of five and six years old. In some regions they are polygynous, meaning males opt for multiple partners. In some, they are polygynandrous, meaning that both males and females take multiple partners. And in some regions, they are monogamous. Their mating system seems to be associated with troop size. For example, monogamy is more prevalent in small groups.
They breed when food is ample and conditions are right, usually from February to March. Females offer copulation calls to males, who then reply with booms or coughs in acceptance.
Females give birth to a single infant after a five- to six-month gestation period and will not mate again for the full year in between pregnancies. Pregnancies rarely yield twins. Mothers share a close relationship with their infants for the first year and tuck them under their bellies. They remain with their babies, nursing them and acting as the primary caregiver until they are weaned. During this time, the young slowly transition from milk to more solid foods, much as humans do. This helps develop their social, physical, and mental abilities as they learn to source and consume nourishment on their own.
The role of adult males and fathers is less defined, but it is presumed they act as protectors for groups. Despite being aggressive and territorial towards their own species, infanticide has not been documented among De Brazza’s monkeys.
As frugivores, the De Brazza’s monkey species is credited with dispersing and scattering seeds during the foraging process and while traveling. Since their cheek-pouches facilitate carrying food away from the source to be consumed, the seeds and other matter that they scatter are dropped far from the mother tree, affording a greater chance for the seeds to propagate without competition, thereby further spreading food-growing plants throughout their habitat. The remaining seeds found in their feces help spread and propagate future growth.
The International Union for Conservation of Nature lists the De Brazza’s monkey as Least Concern (IUCN, 2016), appearing on the IUCN Red List of Threatened Species.
De Brazza’s monkeys are common and widespread in their range, but they are locally threatened by habitat loss and hunting. Their home range is being lost to agricultural and logging industries for timber and farming. In the western part of their territory, they are trapped for bushmeat and, in the eastern part, they are viewed as pests and killed. Natural predators include African eagles, pythons, other primates, and leopards.
The De Brazza’s monkey 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.
Several legally protected habitats exist in the form of reserves and national parks. Areas that specifically protect the De Brazza’s monkey include The Dja Reserve, Cameroon; the Okapi Faunal Reserve and Ituri Forest, Democratic Republic of Congo; Saiwa Swamp National Park, Kenya; the Saiwa Swamp National Park, Republic of Congo; and Odzala-Kokoua National Park, Congo Republic; and the Semuliki National Park, Uganda.
Bushmeat and poaching are combated by regulatory policies, protections, and interdisciplinary approaches.
- IUCN – www.iucnredlist.org
- Southwick Zoo, Cape May County Park & Zoo websites
- EAZA Best Practice Guidelines, Zoo & Wildlife Solutions, Ltd.
- The Primate Family Tree: the Amazing Diversity of our Closest Relatives, Ian Redmond, 2011
Written by Dana Esp, July 2023