DE BRAZZA'S MONKEY

Cercopithecus neglectus

Geographic Distribution and Habitat
Named after explorer Pierre Savorgnan de Brazza, the strikingly beautiful De Brazza’s monkey is native to Central Africa. Members of this old world monkey species are spread across a large geographic area, which includes Angola, Cameroon, the Central African Republic, the Democratic Republic of Congo, Congo, Equatorial Guinea, Ethiopia, Gabon, Kenya, South Sudan and Uganda.

With a strong preference for riverine, swamp, semi-deciduous or acacia-forested areas with dense vegetation, this guenon, also called the swamp monkey, typically settles no further than one mile away (1.6 km) from a water source and never travels more than 0.3 miles (0.48 km) a day when foraging.

De Brazza's monkey range, IUCN 2019

Size, Weight, and Lifespan
Male De Brazza’s monkeys are much larger than females. They grow up to 25 inches (63.5 cm) and weigh up to 17 lbs (7.7 kg), whereas females may grow to 16 inches (40 cm) and weigh up to 9 lbs (4 kg).

Sexual dimorphism offers advantages to males in competition for females during breeding periods. Rapid growth rate, or different length in growth periods, might explain variations in body size. 

The longevity of the De Brazza’s monkey in the wild is estimated to be equivalent to that of other guenon species: approximately 20 years for females and 26 for males. In captivity, both males and females can live up to 30 years.

Appearance
With a distinctive white beard, white belly, speckled grayish coat, and black extremities, the De Brazza’s monkey has an elegant appearance. The orange crescent on the forehead, black crown atop their head, and long white stripes on their thighs and rump highlight the unusual beauty of the species. The long black tail is not prehensile, but is useful for balance when climbing trees. Hands and feet have opposable thumbs. Feet are stronger than those of other guenons and are particularly well adapted to walking on forest ground. 

Like mandrillsvervets, and lesulas, male De Brazza’s monkeys have a blue scrotum. The blue color may be an attractive trait for females and is indicative of social status. The coloring is the result of specific collagen fibers that appear blue with the scattering of light over the skin.

Thin downward-slanted nostrils are indicative of an under-developed sense of smell. Expressive round brown eyes have trichromatic vision, which allows the De Brazza’s monkey to distinguish the color red and detect ripe fruit more easily. Strong incisors are useful to cut fruit and leaves and to dissuade rivals from attempting any foolish moves. Large cheek pouches, as large as their stomachs, are perfect to store food while foraging.

What Does It Mean?

Alarm calls:
Specific calls that individuals in a troop make to warn other members of their group of imminent danger – such as predators.

Arthropod:
 
An invertebrate animal (one with no spine) having an external skeleton, a segmented body, and jointed appendages. Includes insects, spiders, and crustaceans. 

Cheek Pouches:

Pockets on the side of the head between the jaw and the cheek that some animals have to store food.

​Cutaneous scent gland:
Any specialized skin gland that allows an animal to emit odors as sexual or defensive signals.

Polyspecific troop:
Troops of monkeys belonging to different species.

Prehensile tail:
 
A tail that has the ability to grasp and hold objects.

Riverine:

Related to or situated near a river or riverbank.

Semi-deciduous:
A botanical term referring to plants that lose their foliage for a short period of time; as leaves fall, new ones start growing.

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

Trichromatic vision:
The ability to see in color thanks to three color receptors (rods and cones) at the back of the eye in the retina.  Humans and most Old World monkeys have trichromatic vision – i.e. they distinguish blues, greens and reds.

Visit the Glossary for more definitions

Diet
While omnivorous, the diet of the De Brazza’s monkey primarily consists of fruit and seeds and is supplemented by buds, young leaves, flowers, mushrooms, and arthropods (such as beetles, termites, lizards).

Troops prefer to forage in the mornings and evenings and handpick their food, which they either consume on site or carry away in their cheek pouches. Their home range stands out as the smallest (0.3 miles / 0.48 km) of all guenons and is always close to a water source. Consequently, troops repeatedly visit the same food sites. Pregnant and lactating females tend to eat protein-rich food items. Studies conducted in captivity on several species hosted at le jardin des plantes in Paris indicate that the De Brazza’s monkey favors sweet over bitter-tasting food.

Behavior and Lifestyle
Living in dense forested areas, the De Brazza’s monkey retains some of its mystery as it is fairly quiet and quickly disappears from prying eyes. Studies conducted in different geographic areas reveal that, despite this monkey’s preference for small family parties over polyspecific troops, the size of the group can vary from four to ten individuals, and in rare instances as many as thirty-five individuals.

Daily Life and Group Dynamics
De Brazza’s monkeys are arboreal and spend the majority of their time in the trees and shrubs between the forest canopy and the ground. They are capable swimmers and choose living sites near water sources.

They live in family units that are typically composed of one adult male, one adult female and their young; or one adult male, several adult females and their young. Daughters usually remain with their mothers their entire lives, whereas males leave the family unit when they reach sexual maturity.

Communication
Despite having a vocal sac that inflates to produce loud sounds, De Brazza’s monkeys rarely uses their voices and are not known to use any alarm calls; furthermore, they do not respond to alarm calls of other monkey species. In rare encounters with other groups, the De Brazza’s monkey usually hides and remains silent. If threatened, however, males shake branches, bark and make low pitched boom calls, while females and young hide. Juveniles will call if isolated from their group.

The De Brazza’s monkey uses visual communication very effectively. Intimidation and threatening behaviors include staring with open mouth and lips covering the teeth, or bobbing the head up and down. A threat can be deescalated quickly by retracting the lips and uncovering clenched teeth. Yawning to show canines is another means of telling another individual one is ready to fight, if necessary. Strutting around with an arched tail and slamming branches is a rather demonstrative way for young males to try to establish dominance.

As in all primate species, grooming is a valuable method of calming the spirit. Touch is used during mating and also between mothers and their offspring. Scent is also important in communication; sniffing the mouth of a group-mate allows an individual to learn about food items. Males sniff a female’s genitalia before deciding whether to mate with her or not.

Although their use of scent marking is not well understood in this species, the De Brazza’s monkey has cutaneous scent glands that can be used to mark territory.

Fun Facts

Hermann Schlegel (1804-1884), a German ornithologist and herpetologist who worked for the Dutch Royal Zoological Museum, gave the species its scientific name “Cercopithecus neglectus” in 1876. He published a book about his findings on primates titled “La Monographie des Singes” that year.

The term “Cercopithecus neglectus” means “neglected monkey”.

A De Brazza’s group is called a troop or a tribe.

Like all primates, the inside of the hands and feet of De Brazza’s monkeys have ridges. They also have beautiful black finger nails.

Reproduction and Family
De Brazza’s males are dominant, larger than females, and have access to multiple mating partners. There are reports of monogamous family units in some places. Once fathers, males do not pay much attention to their offspring.

In the wild, the breeding season is February through March or whenever food is most available. Females do not exhibit any visual signs of estrus but likely give off olfactory cues. The gestation period is 5 to 6 months. The interbirth interval is one year. Females give birth to one infant weighing 9 ounces (255 grams) on average. Twins are extremely rare. 

Babies are born covered in golden color fur with their eyes open. At six weeks of age, the white beard and mustache appear; at five months, the coloring of the face matches that of an adult and at six months, the pelage is nearly identical in color to that of the adult. Babies cling to their mother’s belly. They try solid foods at two months and are fully weaned by their first birthday. Males become sexually mature at four years old and leave the maternal group but do not breed until they are six or eight years old. Females become sexually mature at three years old but do not breed until they are five or six years old. 

Ecological Role
The De Brazza’s monkey plays an important ecological role as a seed disperser. 

Conservation Status and Threats
At this time, the species is not considered endangered by the International Union for Conservation of Nature, and is listed as Least Concern (IUCN, 2016). Because De Brazza’s monkeys are so skilled at hiding, there is no accurate assessment of population in the wild. Some countries already have protection rules in place. 

The De Brazza’s monkey is prey to numerous animals, such as large African eagles, leopards, other primates, including humans who hunt them for meat and fur, as well as for the illegal wildlife trade. However, the biggest threat to this monkey’s survival is deforestation. In recent years, large expanses of forest have been cut for logging, or burnt to make space for human housing and agriculture, thereby eliminating and fragmenting large portions of its natural habitat. Forest fragmentation impacts the mobility of the species. As a result, fertility rates are lower and infant mortality is increasing.

Conservation Efforts
The De Brazza’s monkey has been protected from hunting and trapping in Ethiopia since 1975 and is also protected in the Dja Reserve in Cameroon. Hunting authorization is required in many African countries.

Since 1996, the Association of Zoos and Aquariums (AZA) approved a petition to manage the De Brazza’s species under a Survival Species Plan (SSP), which is usually reserved for endangered species. The SSP defines specific guidelines for breeding in order to reduce the loss of genetic diversity of the species.

The De Brazza’s monkey was added to the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). In addition, the species is included in the Bushmeat Crisis Task Force’s list of species it is working to protect.

References:

  • IUCN – www.iucnredlist.org 
  • The Guenons: Diversity and Adaptations in African Monkeys – Mary E Glenn, Marina Cords – 2006
  • www.macalester.edu
  • Oregon Zoo, Lincoln Zoo, Houston Zoo, San Diego Zoo websites
  • Primate Info Network 
  • Animaldiversity.org
  • The Evolution of Primate Societies (p 98) – John Mitani, Josep Call, Peter M. Kappeler, Ryne A. Palombit, Joan B. Silk
  • Primate Societies – edited by Barbara B. Smuts, Dorothy L. Cheney, RobertM. Seyfarth, Richard W. Wrangham and Thomas Struhsaker.
  • Palomar.edu – Primate color vision
  • National Geographic website

Written by Sylvie Abrams, October 2017