The blue monkey or diademed monkey (Cercopithecus mitis) is a species of Old World monkey native to Central and East Africa, ranging from the upper Congo River basin east to the East African Rift and south to northern Angola and Zambia. It sometimes includes Sykes', silver, and golden monkeys as subspecies.
Subspecies
Several subspecies are recognised: Cercopithecus mitis boutourlinii – Boutourlini's blue monkey, found in Western Ethiopia Cercopithecus mitis elgonis – Elgon blue monkey Cercopithecus mitis heymansi – Lomami River blue monkey, found in Congo Cercopithecus mitis kolbi – Kolb's monkey, found in Kenya Cercopithecus mitis mitis – Pluto monkey, found in Angola Cercopithecus mitis moloneyi – Moloney's blue monkey Cercopithecus mitis opitsthosticus Cercopithecus mitis schoutedeni – Schouteden's blue monkey, found in Congo Cercopithecus mitis stuhlmanni – Stuhlmann's blue monkey At times, some of these have been regarded as full species, and additional subspecies have been considered valid, while others are not recognized by all authorities.
Description
Despite its name, the blue monkey is not noticeably blue; it has little hair on its face, and this does sometimes give a blue appearance, but it never has the vivid blue appearance of a mandrill, for example. It is mainly olive or grey apart from the face (which is dark with a pale or yellowish patch on the forehead – the "diadem" from which the species derives its common name), the blackish cap, feet, and front legs, and the mantle, which is brown, olive, or grey depending on the subspecies. Typical sizes range from 50 to 65 cm in length, (not including the tail, which is almost as long as the rest of the animal), with females weighing a little over 4 kg and males up to 8 kg.
Ecology
Habitat
The blue monkey is found in evergreen forests and montane bamboo forests, and lives largely in the forest canopy, coming to the ground infrequently. It is very dependent on humid, shady areas with plenty of water. It eats mainly fruit and leaves, but will take some slower-moving invertebrates. It prefers to live in tall trees, which provide both food and shelter, and is, therefore, like almost all guenons, suffering from the loss of its natural habitat. Where pine plantations replace natural forest, the monkey may be treated as a threat by foresters, since it sometimes strips bark from exotic trees in a search for food or moisture. It is also hunted for bushmeat.
Diet
Blue monkeys eat fruits, figs, insects, leaves, twigs, and flowers. "They are primarily frugivores, with 50% of their diet consisting of fruit, with leaves or insects as their main source of protein, with the rest of the diet being made up of seeds, flowers, and fungi. They rarely eat vertebrates. They eat a variety of plants, but concentrate on a few species, which means their population density is generally dependent on plant species' richness and diversity".
Behavior
Cercopithecus mitis joins with the C. ascanius (red-tailed monkey) for extra protection. Its interactions with red-tailed monkeys include interspecies grooming. Their social system is mainly female because the males leave once they are mature. The males have little to no interaction with the young. C. mitis is very territorial, so the young males must leave quickly to help themselves become more successful. They challenge the dominant male of another family. If they defeat the dominant male, they take over the leadership of that family, and this offers a place to live, socialization, and food supplies for the young males." C. mitis is said to be nomadic.
Social structure
The blue monkeys live in female-philopatric social systems where females stay in their natal groups, while males disperse once they reach adulthood. As a result, blue monkey groups usually consist of one male with several females and infants, giving rise to matrilinear societies. Occasionally, solitary males are observed, which are probably transient, having left their natal group in search of a new group.
Social relationships
In these female-bonded societies, only 5–15% of monkeys' activity budget is occupied by social interactions and the most common social interactions within a group are grooming and playing. Relationships between group members vary: infants interact most frequently with their peers and adult or juvenile females and are rarely seen near adult males.
Alloparenting is common among blue monkeys. The most common infant handlers are juvenile females, and usually one infant is carried by a number of alloparents. One hypothesis is that this allows the infant to learn to socialise at an early stage in life.