Geographic Distribution and Habitat
The crowned monkey—also known as the crested mona monkey, crowned guenon, golden-bellied guenon, or the golden-bellied monkey—is found in west central Africa, particularly from the Cross River in Nigeria and southern Cameroon to Angola (Cabinda) and east into the Central African Republic. They are also present in eastern Congo and the northern Democratic Republic of Congo, as well as in Equatorial Guinea (Bioko and mainland) and Gabon.
There are at least three crowned monkey subspecies:
- Gray’s crowned monkeys (Cercopithecus pogonias grayi) are found in the Sangha River basin of southern Cameroon and from southern Central African Republic to the northern Democratic republic and Cabinda.
- The black-footed crowned monkey (Cercopithecus pogonias nigripes du Chaillu) is endemic to Gabon.
- The golden-bellied crowned monkey (Cercopithecus pogonias pogonias) is endemic to Bioko and the adjacent parts of southern Nigeria and southern Cameroon.
They are found in primary lowland and submontane rainforests and prefer the upper strata of the forest at 66–82 ft (20–25 m) above the forest floor.
Size, Weight, and Lifespan
The crowned monkey is a medium-sized Old World monkey. Body length measures from 12.5 to 21 in (32–53 cm). Males are usually larger in size than females. Their tails are often longer than their bodies, measuring from 26 to 35 in (66–89 cm). Adult females weigh about 8.8 lb (4 kg) while adult males weigh closer to 11 lb (5 kg), though body mass can range anywhere from 4.4 to 13.2 lb (2–6 kg).
They can live between 24 and 30 years in the wild.
Although sexually dimorphic in size, both females and males exhibit similar coloration and patterns. Their brown coat is speckled with gray, and their lower arms, legs, and tail base are all black. The rump, belly, and insides of their legs are golden-yellow. Their faces are mainly dark blue or gray, with a pink muzzle covered in white hairs. The hair surrounding their face is yellow marked with wide black stripes, which run from beside the eyes over to the temples and across the center of the forehead. This forms a small crest, which gives the crowned monkeys their name. Other features include a set of sideburns that have traces of white, yellow, and gray in them.
Males have a distinct blue scrotum, which scientists believe is important for attracting mates.
Like many Cercopithecus species, the crowned monkey has large cheek pouches, which they stuff with fruits and seeds while foraging. They enjoy these snacks at a later time while perched in the forest canopy on their callus-like buttocks patches (known as ischial callosities), which provide comfort while sitting on hard branches.
The crowned monkey is mostly frugivorous: 60–87% of their diet is made up of fruits and seeds. They also eat leaves, flowers, and insects. The cusps of their teeth facilitate grinding food, which aids in the diverse diet of this species.
Crested monkeys, like others in the Cercopithecus genus, are fast foragers. They store food inside their large cheek pouches and continue to eat once they are safe from predators and potential food thieves. Their cheek pouches are quite large—extending from their lower teeth to both sides of the neck—and can store almost as much as their stomachs.
Behavior and Lifestyle
Crowned monkeys are most active during the morning and late afternoon, making them diurnal. They are very agile and leap across large gaps between trees. To manage these acrobatic feats, they start off by running on all fours to the outer end of the tree branch before jumping across to the branch of another tree. It may look like they are flying from tree to tree. They securely land on all four limbs in a vertical posture and continue to travel quadrupedally. Occasionally, they miss their landing and fall to the ground or into the water below. Surprisingly, this does not usually result in injury. They get back up to climb the nearest tree.
Crowned monkey females show no sign of estrus swelling, which typically indicates that females are ready to mate.
As males reach maturity they disperse from their natal group. Crowned monkeys live in groups of 8 to 20 individuals. These groups are typically made up of a single male, several females, and their offspring. Their mating system is polygynous—one male mates with two or more females. Occasionally, males try to overthrow the resident dominant male.
While resting, the monkeys often entwine their tails and engage in a ritualized head display. Social groups of crowned monkeys sometimes associate with other guenon species such as the moustached guenon (Cercopithecus cephus) and the putty-nosed monkey (Cercopithecus nictitans). Together, these mixed species groups provide extra protection from predation. More eyes mean spotting predators—such as hawks—is more likely. It also makes it easier to share information between groups about the best foraging sites.
Being an especially social and vocal species, crowned monkeys have developed a wide variety of calls. Both males and females have vocal sacs that can be inflated to make the calls resonate loudly over distances. Dominant males will make a loud “booming” call to establish territory. It is low in frequency and is used to announce their presence and status and to communicate territoriality. They also make low hacking calls to reorganize their group after a disturbance.
Isolation calls are emitted by infants or juveniles when they become separated from the troop. Adults occasionally emit the isolation call as well, and it can resemble a nasal grunt.
Not much is known about the mating behavior of the crowned monkey, though is it assumed that they form polygynous bonds from their social organization structure (predominantly female groups with few males).
The gestation period is typically 5–6 months. Females give birth to one offspring at a time, but twins do sometimes occur. A female typically gives birth every two years. Birth takes place at night and up in a tree. Females nurse and care for their young for about a year. The male role in parental care is not well-reported. Weaning occurs when the offspring is about a year old.
Sexual maturation occurs between 2 and 5 years of age.
As frugivores, crested monkeys are valuable seed dispersers for their ecosystem. After eating a fruit, a monkey may travel a great distance before their food is digested. They defecate the seed far away from the parent tree, assuring a more diverse forest. Crested monkeys, and guenons in general, are even more effective seed dispersers than other animals thanks to their cheek pouches, which allow them to carry food farther than they could otherwise.
The crowned monkey is listed as Near Threatened on the International Union for Conservation of Nature’s Red List of Threatened Species (IUCN, 2017). Although this species has a large range, it is hunted for bushmeat. Humans are their primary predator and consume these monkeys or trade them commercially for consumption in towns and cities. In addition, there is ongoing forest loss and degradation within their range. Increasing human populations, agricultural expansion, and logging are all threats to the crowned monkey. During the last 20–30 years, road access into once remote forests, even around protected areas, has increased exponentially. This access facilitates hunting and transport of bushmeat to local markets and distant cities.
In Cameroon, Equatorial Guinea, Congo, DRC, and Cabina (Angola), habitat modifications, such as converting the land to farmland and “farm bush,” negatively impact the crowned monkey. Deforestation is expected to greatly increase in the future as industrial agriculture expands, removing the habitat that the crowned monkey and other forest-obligate species so greatly depend on.
The crowned monkey is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), Class B of the EU Wildlife Trade Regulations, and Class B of the African Convention on the Conservation of Nature and Natural Resources. It is also on the list of partially protected species in Nigeria and DRC. In addition, hunting, sale, and consumption of primates in Equatorial Guinea were banned by Presidential Decree in October 2007 (though no specific taxon was mentioned in that law). In Congo, the crowned monkey is on Annex III of the current law, suggesting that it can be hunted for food, but only using traditional methods, and not for commerce or transported away from the initial hunting site (to a different village or other area). Annex III also states that trafficking products of the species are strictly prohibited. In Cameroon and Central African Republic (CAR) they are listed as Class C, which allows them to be hunted but only with a permit.
The crowned monkey occurs in a few protected areas including: Lopé-Okanda (Gabon), the Sangha Trinational (Cameroon-CAR-Congo), and the Dja Biosphere Reserve (Cameroon). They are also found in national parks of Conkouati-Douli, Nouabalé-Ndoki, and Odzala in Congo. Hunting is banned in all national parks where the crowned monkey occurs. So at least this species is protected on paper. However, poor compliance with the law outside of protected areas and even inside some protected areas results in hunting in most of the crowned monkey’s range.
To maintain the crowned monkey population, major conservation actions are needed starting with the education and awareness of this species. Increased management for land and water are needed as well.
Another important action that should be taken into consideration is a revamp of legislation and private sector standards and codes on a national level. This would greatly benefit the crowned monkey by creating laws and policies that protect the species.
One of the most crucial—but toughest—actions would be to increase compliance to laws and policies on a national and sub-national level. This can help the growth as well as the physical condition of the crowned monkey population. Lastly, noninvasive research is needed to not only monitor the crowned monkey, but to understand their population distribution and trends and how they react to certain threats. By doing this, the best conservation actions can be put into place.
- Fleagle, J.G. (1999) Primate Adaptation and Evolution, 2nd Edition. Academic Press, New York.
Written by Tara Covert, February 2020