L’Hoest’s monkey (Cercopithecus l’hoesti), or mountain monkey, is a guenon found in Cameroon and the Congo basin. There are two distinct populations and subspecies of this monkey that are widely separated in distribution. They mostly live in mountainous forest areas in small, female-dominated groups. They have a dark coat and can be distinguished by a characteristic white beard.
L’Hoest’s monkey is a forest monkey that is typical of the moist and high primary forests. The western race is mostly relegated to mountainous regions. They are also found in rain forests in an elevation above 3,281 feet (1000 m), as well as old secondary and mature forests. It has also been found to inhabit isolated forest patches in mountain grasslands. The eastern population occurs in a wider number of habitats. It will occupy a range of different kinds of forested areas. These areas include gallery forest, mature lowland rain forests, wooded grasslands at mountain slopes, and forest borders. However, it also will live on cultivated lands. In lowland forests it shows a preference toward areas where the forest is regenerating. In mountain areas it will frequent the mature, tangled, undergrowth below the broken canopy
It lives in fairly small groups dominated by females and has only a single male. The females are usually related, while the male stays only a couple of weeks or at most a couple of years. The adult male will make very loud and distinct calls. They are active during the day, mostly during early morning and late afternoon. They sleep in trees in a sitting position, usually either holding branches or each other. When they are alarmed or see they are being observed they will flee and take shelter in trees. They become very still. They are mostly terrestrial.
This monkey breeds seasonally, which depends on the area. After about a five-month gestation period, a single young will be born. The mother gives birth typically at night and where ever she happens to be at the time. Birth usually occurs at the end of the dry season. She will eat the placenta and lick the baby clean while it hangs onto to her belly. The other females in the group will show much interest in the newborn and will try to hold it. After a few months nursing becomes less frequent. This will continue for about two years when there is another birth. When male offspring reach sexual maturity they will leave the group. In captivity they have been known to live for more than 30 years.
In the wild it is primarily an herbivore. They will mostly eat fruit, mushrooms, herbs, roots, and leaves. It will also occasionally eat eggs, lizards, and small birds.
It has a short, dark brown coat, with a chestnut color across the back and a dark belly. Its cheeks are light gray with a pale moustache. The eastern population has a characteristic and prominent white bib. The western race has a smaller one. The western population however has a facial mask of a black nose and black mouth. In body length it is 12.5 to 27 inches, with a 19 to 39 inch tail. The male weighs about 13.23 lbs (6 kg), while the smaller female weighs 7.72 lbs (3.5 kg). Its tail is long and hook-shaped at the end. They are born fully coated and with their eyes open.