Silvery lutung

The silvery lutung Trachypithecus cristatus, also known as the silvered leaf monkey or the silvery langur, is an Old World monkey. It is arboreal, living in coastal, mangrove, and riverine forests in Pen The silvery lutung is a medium-sized monkey with a long, non-prehensile tail. It has grey-tipped, dark brown or black fur, giving it a uniform silvery appearance. 

Unlike some related species, there are no paler markings on the face or body, except for a patch of whitish hair on the groin of females. A crest of fur runs along the top of the head, and the hair on the cheeks is long, often obscuring the ears. The hands and feet are hairless, with dark coloured skin, and have opposable thumbs and toes. Females range from 46 to 51 centimetres (18 to 20 in) in head-body length, with an average weight of 5.7 kilograms 13 lband a tail length of 67 to 75 centimetres 26 to 30 in. Males are slightly larger, from 50 to 58 centimetres 20 to 23 in in length, with an average weight of 6.6 kilograms 15 lb and a tail length of 67 to 75 centimetres 26 to 30 in. Like other langurs, the silvery lutung has a large three-chambered stomach to digest the cellulose found in its herbivorousdiet. This allows for fermentation of food, and has some similarities with the stomach of ruminants. 

The intestine is unusually long, even compared to those of other langurs, and has a number of pouches along its length, which carry out further fermentation of plant matter. The teeth have grinding ridges and other modifications to allow the more efficient processing of tough leaves. insular Malaysia, Sumatra, and Borneo. The silvery lutung is found across Borneo and Sumatra, as well as in parts of the south-western Malay peninsula, the Natuna Islands, and other nearby islands. It inhabits mangrove swamps and nearby forest regions, and generally avoids travelling far from coasts or rivers.The number and identity of subspecies of the silvery lutung is currently debated. The latest analysis confirms the presence of only two subspecies: Trachypithecus cristatus cristatus - Borneo, Sumatra, Natuna IslandsTrachypithecus cristatus selangorensis - Malay PeninsulaHowever, some older sources, such as Mammal Species of the World, still distinguish the silvery lutungs of the Natuna Islands as a separate subspecies, designated T. c. vigilans. 

The silvery lutung is a specialist folivore, including a higher proportion of leaves in its diet than any other colobine monkey. Although it does also eat fruit, and some seeds and flowers, these comprise only 9% of the diet, and it is also able to feed on tougher and more mature leaves than any of its close relatives. Because of these differences, silvery lutungs do not normally live in the same parts of the forest as other monkeys. Where other species are found in the same area, silvery lutungs are more commonly found in the middle canopy of the forest, leaving the higher branches to monkeys with a more frugivorous diet. Local predators able to feed on silvery lutungs include leopards, tigers, dholes, and some large snakes. Binturongs, civets, and various other small carnivores are probably able to feed on infants. Silvery lutungs are unusually susceptible to human diseases, including AIDS, and have therefore been widely used in medical research.