The Tana River mangabey (Cercocebus galeritus)
The Tana River mangabey (Cercocebus galeritus) is a highly endangered species of primate in the family Cercopithecidae. Some authorities have included the taxa agilis and sanjei as subspecies of this species, while others award these full species status.
It is endemic to riverine forest patches along the lower Tana River in southeastern Kenya. It is threatened by habitat loss and degradation, which has increased in recent years. This species was, together with the equally endangered Tana River red colobus, the main reason for the creation of the Tana River Primate Reserve in 1978, but human encroachment within this reserve continues. Recently, it has been suggested that 20,000 hectares of the Tana River Delta should be transformed into sugarcane plantations, but this has, temporarily at least, been stopped by the High Court of Kenya.
Description
Cercocebus galeritus is a species of catarrhine primate belonging to the family Cercopithecidae. Some classify the species Cercocebus agilis and Cercocebus sanjei as subspecies of C. galeritus, while others confer species status. It inhabits the riparian forests of the Tana River basin in south-eastern Kenya. The species is vulnerable to habitat destruction, which has recently increased.
They are medium-sized primates. The fur is yellow-brown and the tip is black. Like other mangabeys, these monkeys have white eyelids and black facial skin. Males measure between 49 and 63 cm and females between 44 and 53 cm. The length of the tail is 40 to 76 cm. Males weigh between 9.6 and 10.2 kg and females between 5.3 and 5.5 kg. Their jaws are adapted for cracking hard nuts, seeds and fruits.
Distribution
Found in Africa, in southeastern Kenya, in the Tana River basin, in 27 fragments along a 60 km strip of flooded forest. The gallery forests of the Tana river basin are home to several primate species: Tan mangabey, vervet, crowned tamarin, Piliocolobus rufomitratus, baboon and two species of galago. This species prefers riparian forests. The range is fragmented because the Tana River is very meandering, with constantly changing water levels. Human activity also contributes to fragmentation.
Lifestyle
Cercocebus galeritus are diurnal animals. They spend most of their time on the ground and often sleep in trees. They form groups of 13 to 36 animals, sometimes in herds of up to 60. Each group consists of several adult males and females. In search of food, they travel a distance of 1.25 km per day. During the dry season, when little food is available, each group guards its territory. During the wet season, when food is abundant, the territories of neighbouring groups overlap and the animals show no aggression towards neighbouring groups. Cercocebus galeritus is hunted by Python sebae, crowned eagle, battle eagle and Nile crocodile.
Nutrition
Omnivorous. Diet includes leaves, seeds, nuts, fruits, insects, bird eggs and small reptiles. Eats under the forest canopy or in the lower branches of trees. They forage 48% of the time, sleep 15% of the time and rest 14% of the time. Their ration consists of seeds and nuts (46.5%), fruits (25.6%). The jaw apparatus is adapted to the consumption of solid food. Its incisors are large and its small molars are enlarged, which helps it to bite nut shells and hard fruit shells. The muzzle is shortened, increasing the power of the bite.
Reproduction
Polygyny is common in groups of Cercocebus galeritus, with one or two adult males in each group. If a group loses a male, it may take in an outside male. Pregnancy lasts 170-180 days, and there is usually one offspring per litter. During the first two months of its life, the calf is cared for by its mother, and in the third month it begins to interact with its mates and with the adult members of the group, but remains strongly attached to its mother.
Cercocebus galeritus on the Red List
The International Union for Conservation of Nature (IUCN) has declared the species endangered. Habitat destruction is the main threat to the population. As of 2008, the habitat has been destroyed by 50% in 20 years. In addition, the Cercocebus galeritus is hunted. These animals are on the list of the "25 most endangered primates". In 1994, there were an estimated 1,000 to 1,200 Cercocebus galeritus left in the wild.
