Red-eared Monkey

The Red-eared Monkey, or Red-eared Guenon, is a small, brightly colored Old World monkey native to the forests of the Gulf of Guinea region, particularly Bioko Island and adjacent parts of Cameroon and Nigeria. It is easily recognized by its striking red nose and ears contrasting with its dark grey-blue body fur. This arboreal species is remarkable for its vivid facial coloration, believed to play a role in species recognition and social signaling. It is considered vulnerable due to ongoing habitat loss and intense hunting pressure across its range.

Bioko Island (Equatorial Guinea) and mainland Cameroon and Nigeria near the Cross River region

Found on Bioko Island (Equatorial Guinea) and in mainland forests of southeastern Nigeria and western Cameroon, particularly around the Cross River and Korup regions; populations are fragmented and patchily distributed.

Altitude and depth

Typically found from sea level up to around 1,500 meters elevation in forested habitats.

Seasonal movements

No true migration or hibernation; some seasonal shifts in ranging behavior may occur in response to fruit availability during wet and dry seasons.

Primarily inhabits lowland tropical rainforest, including primary and secondary forest, as well as forest edges and occasionally disturbed or logged forest with sufficient canopy cover.

Adaptations to its environment

Adapted for an arboreal lifestyle with strong grasping hands and feet, excellent balance, and agility for moving through the forest canopy. Its cryptic body coloration combined with a bright red nose may aid in visual communication in dense, shaded forest environments.

Classified as Vulnerable (VU) by the IUCN due to significant population declines driven by habitat destruction and hunting; populations are believed to have declined by more than 30% over the past three generations.

Estimated population

Exact population numbers are unknown, but the overall trend is declining due to sustained hunting and habitat loss across its range.

Major threats include deforestation for agriculture and logging, bushmeat hunting, and habitat fragmentation, particularly severe on Bioko Island where hunting pressure is intense.

Diseases and parasites

Susceptible to various gastrointestinal parasites and pathogens common among forest primates, including nematodes and protozoan parasites; specific pathogen data for this species is limited.

Protected under national wildlife laws in Cameroon, Nigeria, and Equatorial Guinea; occurs in several protected areas including Korup National Park and parts of the Bioko Biodiversity Protection Program's monitored zones.

Recommended actions

Strengthening enforcement against illegal bushmeat hunting, expanding protected forest areas, promoting community-based conservation, and conducting further population surveys to guide management.

The body fur is generally dark grey to bluish-black, with a reddish-brown to chestnut back and a distinctive bright red or orange nose and ear tufts. The underparts are lighter, often pale grey or white.

Size

Head-body length typically ranges from 40 to 55 cm, with a tail length of 55 to 75 cm.

Weight

Males typically weigh between 3.5 and 5 kg, while females are smaller, weighing around 2.5 to 3.5 kg.

Distinctive features

Distinguished from related guenons by its vivid red nasal patch and reddish ear tufts, which are much brighter than in similar species like Cercopithecus erythrogaster.

Differences between males and females

Males are noticeably larger than females and possess more prominent canine teeth, though coloration is similar between sexes.

Lives in social groups typically composed of one adult male and multiple females with their offspring, ranging from 10 to 20 individuals; groups may also form mixed-species associations with other guenons.

When it is active

Diurnal, being most active during daylight hours when foraging and socializing in the forest canopy.

Diet

Omnivorous diet consisting mainly of fruits, seeds, leaves, flowers, and supplemented with insects and other small invertebrates.

How it feeds and hunts

Forages opportunistically by searching foliage and branches for fruit, insects, and other food items rather than using active predatory hunting techniques.

Communication

Communicates through vocalizations such as alarm calls and contact calls, along with facial expressions, body postures, and scent marking to convey social and reproductive information.

Interactions with other species

Predators include large raptors, snakes, and forest carnivores; the species may also associate with other primate species in mixed-species groups to reduce predation risk.

Role in its ecosystem

Plays an important ecological role as a seed disperser, helping maintain forest regeneration and plant diversity through its frugivorous diet.

Breeding is not strictly seasonal, though births may peak during periods of high fruit abundance; gestation lasts approximately 5 to 6 months, typically resulting in a single offspring.

Raising the young

Females provide the majority of parental care, nursing and carrying infants for several months; other group females may assist in alloparental care.

Maturity and lifespan

Sexual maturity is generally reached between 4 and 5 years of age; lifespan in the wild is estimated at around 20 years, with slightly longer lifespans possible in captivity.

Classification

Class Mammalia > Order Primates > Family Cercopithecidae > Genus Cercopithecus > Species Cercopithecus erythrotis

Subspecies

Cercopithecus erythrotis erythrotis (Bioko Island) and Cercopithecus erythrotis camerunensis (mainland Cameroon and Nigeria), differing slightly in coloration and distribution.

Scientific synonyms

Cercopithecus erythrogaster erythrotis was formerly sometimes used interchangeably, though it is now considered a distinct sister species.

Recent studies

Recent studies have focused on genetic relationships among Cercopithecus species in the Gulf of Guinea region, helping clarify taxonomic boundaries between C. erythrotis and closely related taxa like C. erythrogaster.

Genome and DNA

Detailed genomic studies are limited, though it shares chromosomal characteristics typical of the genus Cercopithecus, with 2n=72 chromosomes similar to related guenons.

Compared with similar species

Closely related to Cercopithecus erythrogaster (Red-bellied Monkey) and Cercopithecus sclateri (Sclater's Monkey), but distinguished by its brighter red nasal and ear coloration and different geographic range.

Its bright red nose has earned it comparisons to a 'clown-faced' monkey among local observers; it is one of the few African primates with such vivid facial coloring; some populations on Bioko Island persist despite extremely high hunting pressure, showing remarkable resilience.

Where and how to see it

Best observed early morning in undisturbed lowland forest areas of Korup National Park (Cameroon) or protected forest reserves on Bioko Island, where guided treks increase chances of sightings.

Risks to humans

No notable risk to humans; it is a shy, non-aggressive species that avoids direct contact with people.

Human uses

Hunted locally for bushmeat, which represents a major threat to its survival; not commonly used in trade or traditional medicine beyond local subsistence hunting.

Myths and legends

In some local Bioko and mainland communities, brightly colored monkeys like this species are sometimes associated with forest spirits or seen as omens, though specific documented folklore is limited.