Silvery Lutung, Trachypithecus cristatus
SILVERY LUTUNG
Trachypithecus cristatus
Geographic Distribution and Habitat
The silvery lutung, also known as the silvered leaf monkey or the silvered langur, is found in numerous areas of Indonesia, including Borneo, Sumatra, Java, and the Natuna Islands, as well as in parts of the southwestern Malay Peninsula and other nearby islands. Within this range, silvery lutungs prefer dense forests; however, their habitat varies depending on the region they inhabit. In the Malay Peninsula, they live in mangrove and sub-coastal forests, whereas in Java and Sumatra, they live in the trees of inland forests. They are also found in bamboo forests, swamp forests, and, occasionally, plantations.
The silvery lutung once had a subspecies called the Selangor silvery langur (T. selangorensis). As of 2013, both species have been recognized as separate by primatologists due to genetics as well as differences in their whiskers. Selangor silvery langurs have long, straight whiskers, while those of the silvery lutung are forward-curled, forming a semi-circular shape resembling a mussel’s shell.
Size, Weight, and Lifespan
Male silvery lutungs weigh an average of 14.5 pounds (6.6 kg), while females average 12.6 pounds (5.7 kg). Head-body length in males ranges from 20.6-22 inches (52.4-56 cm), while that of females ranges from 18.3-19.5 inches (46.5-49.6 cm). Silvery lutungs have long tails, sometimes measuring longer than their body length! The tail length of males ranges from 26.4-29.5 inches (67-75 cm), while that of females ranges from 26-29.5 inches (66-75 cm). These slight differences in size are an example of sexual dimorphism, or noticeable physical differences between genders.
Their average lifespan in the wild is 20 years, while in captivity, they have been known to live up to 31 years.
Appearance
The coat color of silvery lutungs is dark gray, with the tips of their hair a lighter gray, which gives them an overall silvery effect. The groin and underside of the tail are a yellowish color. The face is black, and the black hair atop the head sweeps upward into a point. There are slight variations in hair color, including brown, brownish-gray, or black. Although adult males are slightly larger than adult females, visually distinguishing between the sexes can be difficult. One visible differentiator is white patching on the interior flanks of females, another example of sexual dimorphism. The loooong tail is non-prehensile, meaning it is not used for grabbing or grasping, but rather, to aid in balancing while traveling amongst the branches of trees.
As is typical among colobines, or leaf-eating monkeys, the lower jaw projects out further than the upper jaw. The genus Trachypithecus can be distinguished from other colobines by their prominent nasal bones, well-developed sagittal crest, and recessed brow ridges.
The size of their thumbs is reduced, which makes it easier for them to use brachiating movements while traveling throughout their forest habitats. What are brachiating movements? Brachiation is acrobatically swinging from tree to tree! Their fore and hind limbs are almost equal in length, which is unique for monkeys not native to the Americas.
Newborns have orange hair, and white hands, feet, and faces. Within a couple of days of birth, an infant’s face turns black, just like an adult’s. The hair changes to the adult color within three to five months. What a drastic difference! You’ll find out why there’s such a striking coloration among infants in the Fun Facts section.
Diet
Silvery lutungs are primarily folivores, or leaf-eaters, with leaves making up 91% of their diet. The remaining 9% consists of fruit, some seeds, buds, and flowers.
Silvery lutungs are also able to feed on tougher and more mature leaves than any of their close relatives. Due to these differences, silvery lutungs do not normally live in the same parts of the forest as other monkeys. Silvery lutungs are more commonly found in the middle canopy of the forest, leaving the higher branches to monkeys with a more frugivorous, or fruit-based, diet.
Many of the leaves they eat contain plenty of cellulose (the primary chemical that forms the main structure of plants), so like other members of their genus, the silvery lutung has a multi-chambered stomach to help digest this tough material. They also spend a large portion of their day resting so digestion can run smoothly.
Behavior and Lifestyle
Silvery lutungs are primarily arboreal, preferring to spend the vast majority of their time in the trees. They occasionally descend to the ground, but only to travel from place to place. They are diurnal, meaning they are most active during daylight hours until sunset. They are also quite shy, especially when near humans. In addition to humans, when threatened by predators such as leopards, dholes, tigers, and some large snakes, they quickly retreat back into the trees.
While traveling through the trees, silvery lutungs brachiate from tree to tree. When traveling on the ground or walking and climbing through the trees, they do so quadrupedally, or on all fours. Walking is typically a group activity.
Social play primarily occurs between juveniles and infants of both genders; however, all age groups have been observed participating in play. Wrestling and locomotor play are the most common forms of play. Locomotor play is when an individual swings from branches or drops to the ground from branches, but in a repeated motion like a circuit. Play fighting also occurs among juvenile males and sub-adult males.
With regard to an activity budget, according to one resource, the following metrics have been documented: 60% of the day is spent resting, 15% is spent foraging, 10% is dedicated to traveling, and another 10% is spent engaging in social activities such as grooming and playing, and 2% is dedicated to “other”.
Rather than construct nests, silvery lutungs will retreat to a single tree to sleep at night.
Grey and black adults, but orange and white babies!? Yes! Scientists have theorized several reasons as to why baby silvery lutungs (along with those of other Trachypithecus langur, lutung, and leaf monkey species) are so brightly colored. Three dominant theories are: camouflage within their forest habitat, the ability to be easily found by Mom should the little ones wander off, and to encourage allomothering (taking care of a baby that isn’t one’s own).
Silvery lutungs live in a uni-male social structure, meaning groups consist of a single adult male, several adult females, juveniles, and infants, totaling 9-40 individuals. Each group occupies a home range of 49-106 acres (20-43 ha), although these may overlap with those of neighboring groups. All-male social groups, known as bachelor groups, also exist. Sometimes solo males venture around, searching for a new group to join. A male, whether solo or from a bachelor group, will challenge the dominant male of a family group in the hopes of taking over leadership.
Besides aggressive interactions with non-related individuals, silvery lutungs are a fairly peaceful species, and have low levels of aggression among others within their group. Some suggest these low levels of aggression are associated with the abundance of food within their habitat and the manner in which they feed. As a result of the ample food supply, silvery lutungs do not need to engage in socially cooperative behaviors in order to feed successfully. This diminishes the need for social interaction between group members.
Despite the peaceful atmosphere within a group, occasional conflicts may also arise between groups, mostly over territory. These conflicts usually occur in areas in where home ranges overlap. Males chase away males from other groups. Other fighting behaviors include slapping, pulling, and biting. Adult males emit loud vocalization calls when neighboring groups come in contact with one another, an additional means of protecting the group and territory. Meanwhile, they share habitat and peacefully mingle with other primate species, such as the proboscis monkey (Nasalis larvatus), and long-tailed macaques (Macaca fascicularis).
With regard to their daily routine, right before sunrise, groups set out to forage throughout their territory, traveling 656–1,640 feet (200–500 m) daily. The adult male of the group leads the other group members by guiding them with vocalizations (a “kwah” sound). During the late morning, individuals rest. Juveniles and infants prefer to stay close to adult females while resting. At sunset, the group retreats to a single sleeping tree to spend the night.
Finally, upon reaching sexual maturity, females remain in the group for life, while males leave shortly after reaching adulthood, living in small bachelor groups or living alone until they can take over an established group. Within the group, males dominate females, and females with young dominate those without.
Researchers have described the silvery lutung as expressionless, solemn, and slow-moving. Although they are somewhat quiet and less vocal than other closely related species, they do have various vocalizations, at least 13 different ones! A “ku” sound is emitted by infants when they are in a happy state. A “ho” sound is used by young males and females over short distances to address each other. “Ku-ku” calls are uttered by adult females while greeting each other. In addition, they have alarm calls, threat calls, territorial calls, and calls to express fear, excitement, satisfaction, and anger.
This species also communicates via touch through social grooming and embracing. Other non-vocal communications include yawning to indicate tension or excitement, branch-shaking, head-shaking, and chasing.
Silvery lutungs are polygynous, meaning one male mates with multiple females. To attract the male’s attention, the female makes side-to-side motions with her head. Females usually give birth to no more than one infant every 18 to 24 months, after a gestation (pregnancy) period of 181-200 days. There is no defined breeding season; however, births peak from December to May.
Infants are born well-developed and in possession of a strong grip for holding onto their mother. Mothers nurse their young for several months after birth, and will care for the young of other mothers in the group, even allowing them to nurse. This is called allomothering. Females and males both teach their young, play with them, and protect them. Infants usually approach males to be carried and to play.
Weaning from Mom’s milk occurs at 18 months. Upon reaching maturity, females remain within their natal group, while males set off to form a group of their own. On average, females first give birth at 35 months of age.
As fruit and seed-eaters, silvery lutungs aid in the regeneration of their forest habitats by dispersing seeds through their feces as they move around the habitat. In addition, by feeding on young leaves, they largely strip trees of these leaves. This stimulates the trees to recover by producing a new set of young leaves, thereby increasing their productivity and growth rate. They may also play a role in pollination when they eat flowers. Like bees and butterflies, they collect pollen from flowers while consuming them. They then deposit the pollen on each flower they visit, thereby pollinating the plants. Finally, as a prey species, they also play a role in feeding local predators within their range.
The International Union for Conservation of Nature lists the silvery lutung as Vulnerable (IUCN, 2015), appearing on the IUCN Red List of Threatened Species.
The disappearance of suitable lowland habitat due to forest fires, logging, and land clearance (especially for oil palm plantations) is a major threat for the silvery lutung, especially in Peninsular Malaysia and Borneo. Silvery lutungs are also hunted locally for meat, especially in Sarawak, and heavily traded as pets both locally and nationally, especially in Sumatra.
The silvery lutung is listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.
The silvery lutung is known to dwell in at least four protected areas: Bukit Barisan Selatan National Park and Gunung Leuser National Park in Indonesia, and Bako National Park and Taman Negara National Park in Malaysia.
Conservation actions such as site/area, and resource and habitat protection, along with site/area and harvest management, are needed to further protect the silvery lutung. Along with these actions, further research is needed on the silvery lutung’s population size/distribution/trends, life history, ecology, human harvest/use, and threats. Additionally, monitoring of their population trends is necessary so that this sensational silver monkey survives the plight of endangerment and extinction.
- https://www.alltheworldsprimates.org/Members/Home/MasterPrimate.aspx?tid=849
- https://animalia.bio/silvery-lutung
- https://www.bioexplorer.net/animals/mammals/monkeys/silvered-langur/
- https://critter.science/the-silvery-lutung/
- https://en.wikipedia.org/wiki/Colobinae
- https://en.wikipedia.org/wiki/Silvery_lutung
- https://www.iucnredlist.org/species/22035/17959977
- https://www.jungledragon.com/specie/9508/silvery_lutung.html
Written by Sienna Weinstein, March 2025