Silvery lutungs are medium-sized Old World monkeys with a long, non-prehensile tail. They have grey-tipped, dark brown or black fur, giving the animals 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-colored skin, and have opposable thumbs and toes.
Silvery lutungs are found across Borneo and Sumatra, as well as in parts of the south-western Malay peninsula, the Natuna Islands, and other nearby islands. These monkeys live in mangrove swamps and nearby forest regions, and usually avoid travelling far from coasts or rivers.
Silvery lutungs are diurnal and travel in groups of around 9-40 individuals with one adult male and many adult females communally caring for infants. They rarely leave the trees, which provide them protection from ground-dwelling predators, and rapidly flee if threatened. During the day, these monkeys may travel up to 500 metres (1,600 ft) through the forest and at night then the entire group will shelter in a single tree. The social structure of silvery lutungs is matrilineal and harem based. Females remain in the group for life, while males leave shortly after reaching adulthood. Within the group, males dominate the females, and females with young dominate those without. In order to communicate with each other Silvery lutungs make at least thirteen different vocalizations, with the most common being used by adult males defending their territory. Other vocalizations express fear, anger, excitement, and satisfaction, in addition to various calls made by infants.
Silvery lutungs are polygynous whic means that one male mates with more than one females during the breeding season. The female attracts the male by making side-to-side motions with her head. Silvery lutungs breed year round, with no clear breeding season, although each female typically gives birth once every 18-24 months. Females give birth to a single infant after a gestation period of 181-200 days. The young weigh about 400 grams (14 oz) and are well developed, with a strong grip for holding onto the mother. Infants are born with orange fur, and with white hairless skin on the face, hands, and feet. The skin rapidly changes to the dark adult colour, but the fur does not reach the adult pattern for 3-5 months after birth. The young are cared for by females communally, and are not weaned for 18 months, even though the biological mother stops lactating after just 12 months. The young become reproductively mature almost as soon as they finish weaning, and, on average, females first give birth at 35 months of age.
The major threat facing Silvery lutungs is the destruction of their habitat due to logging, the development of oil plantations and forest fires. These monkeys are also threatened by hunting for meat and by capture for the pet trade.
The IUCN Red List and other sources don’t provide the number of the Silvery lutung total population size. Currently, this species is classified as Near Threatened (NT) on the IUCN Red List and its numbers today are decreasing.