Roloway Monkey, Cercopithecus roloway
ROLOWAY MONKEY
Cercopithecus roloway
Geographic Distribution and Habitat
The Roloway monkey (Cercopithecus roloway), also known as the Roloway guenon, is native to Côte d’Ivoire (Ivory Coast) and Ghana. Historically, this species had a range covering a broad swath of the southern Ivory Coast. Today, however, this critically endangered species is found in just a few forests: Tanoé forest and the Dassioko Sud and Port Gauthier forest reserves in Côte d’Ivoire, and the Kwabre forest in Ghana.
Roloway monkeys live in moist evergreen forests, moist semi-deciduous primary forests, old secondary lowland forests, and swamp forests. Because their lifestyle is built around dense tree canopies, Roloway monkeys are very susceptible to human disturbance. Once logged, the tall trees that make up a forest canopy are not easily replaced.
They are now extirpated, or locally extinct, in most of their previous range. Scientists have been documenting the declining population of Roloway monkeys since the mid-1990s and estimate that fewer than 2,000 individuals remain in the wild today.
Many of the remaining pockets of habitat for Roloway monkeys are still intact, in part because their swampy nature makes it extremely difficult for humans to move through the forest or grow crops. The Tanoé forest is often flooded, for example, with an average annual rainfall of 55-63 inches (140-160 cm) and a long wet season from March to December. The long rainy season also means that fruit is widely available for Roloway monkeys to eat for most of the year. Still, even in the hard-to-access Tanoé forest, human activities like fishing and medicinal plant harvesting threaten the remaining Roloway monkey habitat.
The coldest time of year is August, when temperatures dip to 66 °F (19 °C). February and March are the hottest months, with temperatures up to 91 °F (33 °C). Roloway monkeys mostly live at elevations around 492 feet (150 m), but have also been found as high up as 984 feet (300 m).
Roloway monkeys were once considered to be a rare subspecies of Diana monkeys (Cercopithecus diana). Although they look remarkably similar, the Roloway monkey is now considered by most—but not all—researchers to be a full species. This revised classification has helped draw greater attention to its conservation, as subspecies often receive less conservation attention than full species. The IUCN Red List recognizes the Roloway monkey as a distinct species.
Size, Weight, and Lifespan
Roloway monkeys are the largest of the guenon monkeys. Sexual dimorphism, or physical differences between the sexes, is evident, with males being larger than females. Male Roloway monkeys weigh an average of 11 pounds (5 kg), more than twice the weight of females, who average 5 pounds (2.3 kg). Measured from head to rump, males are 25 inches (63.6 cm) long and have a tail that is 33 inches (83.9 cm) long. In comparison, females measure 22.2 inches (56.5 cm) from the head to the rump, and their tails are 29.7 inches (75.5 cm) in length.
Although the lifespan of Roloway monkeys is unknown, the closely related Diana monkey can live up to 34 years.
Appearance
Who’s that tuxedo-wearing monkey with the long, white beard? It’s the striking Roloway monkey! These guenons have a mostly black body with a dark brown-reddish patch on their lower back. A white stripe runs across the upper thigh. Their “outfit” is completed with white-light yellow inner thighs, contrasting with their white beards and bellies, giving Roloway monkeys an undeniably sophisticated look. This bright coloring isn’t just decorative—it also helps individuals see others across the forest, allowing them to identify one another and communicate over long distances.
Although Roloway monkeys look similar to Diana monkeys, a few key distinctions set them apart. Roloway monkeys have a wider brow line, narrower face mask, and ear tufts that are not present in the Diana monkey. The Roloway monkey also has pale yellow inner thighs—not red, like the Diana monkey—and a longer beard. These distinctions also likely help the two species identify one another and avoid mating, and thereby produce hybrids that might not survive to adulthood.
Roloway monkeys belong to a genus commonly known as guenons. Species in this group are known to have enormous cheek pouches that they can fill with food while foraging.
Diet
Roloway monkeys are omnivorous and eat an incredibly diverse diet including more than 130 plant species. Most frequently, they eat mature fruits, insects and other bugs, oil-rich seeds, and young leaves. The three most important trees in their diet are Pycnanthus angolensis, a tree in the nutmeg family, Piptadeniastrum africanum, a tree in the legume family, and Santaloides afzelii, a climbing shrub.
The Roloway monkey’s diet varies depending on the season. A group in Ghana’s Bia National Forest ate more insects in the wet season and more mature fruit in the dry season. This is just one known instance of seasonal variation, however, and is not enough information to be sure that all Roloway monkeys eat this way.
Their diet is very similar to that of the putty-nosed monkey (Cercopithecus nictitans), and the two species may competitively exclude each other. In other words, you will not find the two species together in one area, because competition over the same foods drives each species away from the other.
Behavior and Lifestyle
Roloway monkeys are highly arboreal and spend most of their time in the dense canopy of the forest. When sleeping and eating, they’ll go even higher to the emergent layer, where the tallest trees poke above the canopy. Roloway monkeys get around with a combination of climbing, leaping, and walking on all four legs.
In 2002, scientists in Ghana’s Bia National Park observed that a group of 14-15 individuals had a home range of 470 acres (190 ha). A separate study done in the Tanoé swamp forest of Côte d’Ivoire found an average group size of 6.85 individuals and a population density of 36 individuals per km².
When they’re searching for food, Roloway monkeys often spread out more than 328 feet (100 m) from the others in their group. On a typical day in the dry season, Roloway monkeys will usually travel an average of 1.4 miles (2280 m). During the wet season, their range compresses down to an average of 0.9 miles (1505 m), likely because that is when there are more insects and fruit, so they don’t have to travel as far to find food. During these rainy months, Roloway monkeys tend to associate with white-thighed colobus monkeys (Colobus vellerosus), spending an average of 4.6 hours together each day. As the colobus move through the trees searching for leaves, they may inadvertently flush insects from their hiding places. Roloway monkeys appear to take advantage of these disturbed insects, making the association a productive foraging strategy.
Roloway monkeys are diurnal, meaning they are active during the day and go to sleep at night. They spend more than half their time 65-98 feet (20-30 m) off the ground. Most of the remainder is spent venturing just 33 feet (10 m) above or below this baseline; very infrequently do Roloway monkeys go lower than 16 feet (5 m) off the ground.
As guenons, Roloway monkeys belong to one of the most diverse groups of African primates. There are at least 33 guenon species, each with a unique ecological role.
Roloway monkeys spend long periods of time eating, traveling, and even sleeping near other monkeys. This includes the white-naped mangabey (Cercocebus lunulatus) and the olive colobus (Procolobus verus), as well as other arboreal guenons like the lesser spot-nosed monkey (Cercopithecus petaurista) and Lowe’s monkey (Cercopithecus lowei). In a survey of Roloway monkeys in the Tanoé forest, they spent 44.7% of their time with other species and 55.3% with their own kind.
The closely related Diana monkey is also popular with other monkeys, likely because they are vigilant and are quick to sound the alarm when they spot a predator. It’s plausible, but not yet confirmed, that Roloway monkeys may behave similarly.
Roloway monkeys typically live in groups of 15-20 individuals. These groups are territorial and defend their space by making loud calls–heard more than 0.9 miles (1.5 km) away.
For most of the year, there is only one adult male in the group. He frequently mates with several females at once and is the only one who initiates relationships. Young male Roloway monkeys may sneak away from this powerful male for one night, but the romantic getaways never last longer than that. Once the young male reaches maturity, he will either leave or be forced out.
During the non-breeding months between November and January, however, the resident male may sometimes tolerate a second adult male. Otherwise, if another male tries to join the group, the resident male will boot him out. Scientists have never observed a group of all males.
Adult male Roloway monkeys use croak calls for many reasons: as an alarm call when they’re threatened, in aggressive encounters with other males, and also as a general territorial call when they’re settling in for the night. Members in the same group, including juveniles, use whistle calls to check in with one another as they travel and eat.
Other guenon species also use grunts, chitters, head-bobs, and facial expressions to communicate with their group. The closely related Diana monkey has an impressive array of alarm calls that can specify which predator is nearby. Whether the Roloway monkey shares this rich vocabulary requires further research.
Roloway monkeys can also communicate through touching and grooming each other. This serves the dual purpose of improving social bonds within the group and improving individual health by removing any insects and parasites from their fur. Additionally, they use their sense of smell to sniff food and determine if it should be eaten or not.
There has been little observation of how Roloway monkeys mate in the wild. The little we know for sure is that scientists have seen a male initiating mating with several females. This likely means that, like the closely related Diana monkey, Roloway monkeys have a polygynous mating system, wherein one male mates with many females.
The closely related Diana monkey reaches sexual maturity between 3 and 4 years of age. Females have pregnancies lasting 4-5 months, and normally give birth to one offspring at a time. When a male comes of age, he leaves his birth group, hoping to find a group of his own, while a female spends her whole life with the group she was born into. We can assume the same for Roloway monkeys.
Roloway monkeys play an important role in their forest habitat. By eating and dispersing plant matter, such as fruits and seeds, they contribute to the growth and diversity of plant life in their ecosystem. Roloway monkeys also provide pest control by eating insects, which helps keep the ecosystem balanced.
Without Roloway monkeys, the greater West African forest ecosystem would suffer from less plant biodiversity and be thrown out of balance. Insects that the Roloway monkey eats, lacking a predator, might grow in population. Predators of the Roloway monkey—such as birds of prey, leopards, and other larger species—might have less to eat and likely shrink in population. These effects can ripple throughout the ecosystem to catastrophic effect.
The International Union for Conservation of Nature lists the Roloway monkey as Critically Endangered (IUCN, 2019), appearing on the IUCN Red List of Threatened Species. Although this species once occurred in many protected areas, a lack of enforcement on human development and hunting has destroyed the forests of West Africa, leaving only a handful of protected areas where Roloway monkeys are thought to live. Researchers estimate that between 1991 and 2018, the Roloway monkey experienced more than an 80% decline in population.
Like many primate species, the Roloway monkey is heavily impacted by habitat degradation and loss. Agricultural development, logging, and charcoal cultivation are causing large-scale deforestation in the Roloway monkey’s habitat. This change is especially stark in Côte d’Ivoire, where 17% of the country’s tree cover was lost between 2001 and 2017. The spread of cocoa farming and a growing human population in the southern forest zone are exacerbating this habitat loss.
Hunting and the bushmeat trade are also major threats to Roloway monkeys, especially in Ghana. Roloway monkeys are a conspicuous target for hunters due to their relatively large size and distinctive coats. Although many forests should otherwise be suitable habitats, poor enforcement of hunting laws has severely affected the species. Today, there are no surviving Roloway monkeys in many regions where they once lived, including several forest reserves and Bia and Nini-Suhien national parks.
The Roloway monkey is listed in Appendix I 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. As a species listed in Appendix I, Roloway monkeys cannot be traded for any commercial purposes.
The Roloway monkey is listed on Class A of the African Convention on the Conservation of Nature and Natural Resources, the highest level of protection.
Despite once inhabiting many protected areas and forest reserves, the Roloway monkey has unfortunately been extirpated from nearly all the places they formerly occupied. In the 1990s in Côte d’Ivoire, Roloway monkeys could be found in the Yaya Forest Reserve, Niégré Forest Reserve, Bolo Ouest Forest Reserve, and Marahoué National Park. Today, they are no longer there. There are rumors that some Roloway monkeys persist in the Dassioko Sud forest reserve and Port Gauthier forest reserve, but the only area with a confirmed population of Roloway monkeys is the Tanoé forest.
Similarly, in Ghana, Roloway monkeys can no longer be found in the Krokosua Hills Forest Reserve, Ankasa Conservation Area, Bia National Park, and Dadieso Forest Reserve, where they once lived. The only place with a confirmed population is the Kwabre forest.
There are some efforts to develop conservation programs involving local communities near the Tanoé and Kwabre swamp forests. These are nascent, however, and are still working towards involving the appropriate national government agencies and international conservation organizations. Scientists also hope to conduct further surveys to learn more about the remaining Roloway monkeys in Tanoé and Kwabre and determine if there are any other viable populations elsewhere.
- https://www.iucnredlist.org/species/4232/92384429
- https://portals.iucn.org/library/sites/library/files/documents/2015-033.pdf
- https://www.alltheworldsprimates.org/
- https://www.nature.com/articles/ncomms5266
- https://www.researchgate.net/figure/Reopened-logging-road-through-Bia-Resource-Reserve-January-2006_fig3_363671305
- https://link.springer.com/chapter/10.1007/0-306-48417-X_23
- https://scispace.com/pdf/the-diurnal-primate-community-of-the-tanoe-forest-species-tlsfnq9nqz.pdf
- https://doi.org/10.4172/2157-7625.1000126
- https://www.cambridge.org/core/journals/oryx/article/three-monkeys-nearing-extinction-in-the-forest-reserves-of-eastern-cote-dlvoire/8BE8B0F92F2E0BF1079B420678930EDC
- https://karger.com/fpr/article-abstract/85/4/244/143729/Sniffing-Behaviours-in-Guenons?
Written by Jiayu Liang, June 2026