The black colobus (Colobus satanas), or satanic black colobus, is a species of Old World monkey belonging to the genus Colobus. The species is found in a small area of western central Africa. Black colobuses are large, completely covered with black fur, and like all other Colobus monkeys, do not have a thumb. The species has faced large declines in population due to habitat destruction and hunting by humans, and was consequently listed as Vulnerable on the IUCN Red List in 1994. The black colobus monkey is one of five recognised species in the genus Colobus. The black colobus is the oldest species in this genera and is thought to have diverged 3-4 million years ago. There are two subspecies of black colobus monkey: The word 'Colobus' comes from the Greek word for 'mutilated', as all Colobus monkeys only have a short stump where the thumb would be. The word 'satanas' means 'the accuser' or 'the devil' in Greek. The black colobus monkey is a large species with a head-body length of 50–70 cm and a long tail of around 80 cm. As in all Colobus species, the black colobus has a slender build and ischial callosities - tough pads of skin on the rump. There is little sexual dimorphism between the two sexes - adult males can weigh between 10–15 kg, whilst females weigh between 10–11 kg. The black colobus is covered in black fur apart from the ears and face, and has longer hairs on its cheeks and forehead. Unlike other species of colobus monkey, black colobuses have no white markings. The two subspecies of black colobus look very similar, although the fur of Colobus s. satanas is slightly longer and fluffier. There is currently not enough data to estimate the life expectancy of the species. The black colobus monkey is found in Equatorial Guinea, south west Cameroon and central and north-western Gabon. Small populations may also occur in the north of the Republic of the Congo. The subspecies C.s.satanas is only found on Bioko Island, off the coast of Cameroon. The distribution of the black colobus has decreased dramatically - the species is now rare or absent in some areas of its range due to its habitat being destroyed for logging. Black colobuses are known to live at low densities, but there is currently no total population estimate for the species. One of the largest remaining populations of the species, consisting of 50,000-55,900 individuals, is found in Lope Reserve, Gabon. Other remaining large populations are found in the Foret des Abeilles in central Gabon and Douala-Edea Reserve in Cameroon. The black colobus is an arboreal species that lives high in the canopy of dense rainforest and occasionally coastal sand dune or wooded meadows. Black colobuses are unable to survive in secondary forest that has regrown after a major disturbance such as logging and therefore tend to avoid areas populated by humans. The black colobus cannot be bred in captivity due to the food and habitat it requires. Black colobus monkeys are herbivores and feed predominantly on seeds. Their robust, flat teeth allow them to chew tough seeds easily. This diet means that the species plays an important role as seed dispersers in the ecosystem. Black colobuses also eat large amounts of leaves, in particular lianas, as well as flowers, buds and unripe fruits. Unlike most primates, Colobus monkeys have multi-chambered ruminant stomachs which allow them to easily digest these leaves. Younger leaves and seeds are preferred, as these are rich in nutrients and contain lower amounts of digestion-inhibiting compounds such as tannin. However, the black colobus monkey can withstand high levels of these poisonous compounds and can therefore eat food that is undigestable to other colobus monkeys. This means they can live in areas unoccupied by other species. Black colobus monkeys have also been observed eating soil, which may be to ensure that they have enough minerals such as sodium in their diet.