JAVAN LANGUR
Trachypithecus auratus
Geographic Distribution and Habitat
The Javan langur (Trachypithecus auratus), also known as the Javan lutung, ebony langur, and ebony leaf monkey, is an Old World monkey that lives in Java, Bali, and the Indonesian island of Lombok. They inhabit inland forests of western Indonesia as well as the southern coastline. A vast amount of forest types are home to the Javan langur, such as mangrove, beach, lowland, and freshwater swamp. Deciduous forests and montane forests up to elevations of 11,482 ft (3,500 m) are also prime real estate for these individuals. The interior and edges of rainforests are common places for them to inhabit, as well as the primary and secondary forests of the Dieng Mountains in Java.
Javan langurs are divided into two subspecies—the Eastern Javan langur, or spangled ebony lutung (Trachypithecus auratus auratus), and the Western Javan langur (Trachypithecus auratus mauritius)—which inhabit different areas of these ranges. The Eastern Javan langur resides in eastern Java and out west to Gunung Ujungtebu; its rare orange morph has a more restricted distribution, between Blitar, Ijen, and Pugeran, Java. The Western Javan langur resides in western Java, up to the north coast from Jakarta, inland to Bogor, Cisalak, and Jasinga, southwest to Ujung Kulon, then along the south coast to Cikaso or Ciwangi.
The Javan langur (Trachypithecus auratus), also known as the Javan lutung, ebony langur, and ebony leaf monkey, is an Old World monkey that lives in Java, Bali, and the Indonesian island of Lombok. They inhabit inland forests of western Indonesia as well as the southern coastline. A vast amount of forest types are home to the Javan langur, such as mangrove, beach, lowland, and freshwater swamp. Deciduous forests and montane forests up to elevations of 11,482 ft (3,500 m) are also prime real estate for these individuals. The interior and edges of rainforests are common places for them to inhabit, as well as the primary and secondary forests of the Dieng Mountains in Java.
Javan langurs are divided into two subspecies—the Eastern Javan langur, or spangled ebony lutung (Trachypithecus auratus auratus), and the Western Javan langur (Trachypithecus auratus mauritius)—which inhabit different areas of these ranges. The Eastern Javan langur resides in eastern Java and out west to Gunung Ujungtebu; its rare orange morph has a more restricted distribution, between Blitar, Ijen, and Pugeran, Java. The Western Javan langur resides in western Java, up to the north coast from Jakarta, inland to Bogor, Cisalak, and Jasinga, southwest to Ujung Kulon, then along the south coast to Cikaso or Ciwangi.
Javan langur geographic distribution. Map credit: Chermundy and IUCN
Size, Weight, and Lifespan
The Javan langur is between 17.3 and 25.6 in (44–65 cm) in body length, with their tail adding an additional 24–38.6 in (61–98 cm). They weigh between 15 and 16 lbs (6.8–7.26 kg) and may live up to 20 years in the wild. Appearance
The appearance of Javan langurs is largely based on which subspecies they belong to: the Eastern Javan langur (Trachypithecus auratus auratus) or the Western Javan langur (Trachypithecus auratus mauritius). Eastern Javan langurs have glossy black hair with a brownish tinge on the sideburns, ventrum, and legs. The skin of their faces, palms, and soles is black. The rarer morph is a deep orange color with a yellowish tinge along the limbs and around the ears and the ventrum. The skin of the orange morph is depigmented and freckled. Western Javan langurs are also glossy black with slightly less brownish tinge along the sideburns, ventrum, and legs. Sexually dimorphic, females have yellowish white pubic patches and males do not. Babies are born with orange coloration and later grow darker hair, which is a common characteristic of weaned langurs. 
Diet
The menu of the Javan langur consists of leaves and flowers, making them herbivorous. They also consume fruit and insect larvae. Like other langur species, Mother Nature has outfitted Javan langurs with enlarged salivary glands and sacculated stomachs capable of digesting the high cellulose content of the plants that they consume. Low fiber plant materials remain in the stomach longer and require ruminant-like processes for complete digestion. Thus, langurs can eat tougher plant matter that other species cannot, including some otherwise toxic plants. This facilitates absorbing the greatest amounts of nutrition from their diet while reducing competition with other species for resources. Through these physiological adaptations, Nature allows them to not simply survive, but to flourish. Behavior and Lifestyle
Javan langurs are diurnal and arboreal. Because the leaves they consume provide them with both nutrition and water, they rarely visit the ground. They travel from tree to tree in the forest canopy, well above the forest floor. Infant care is shared among all females in a troop. This is referred to as allomothering and ensures that each infant is given care and attention, maximizing their survival chances and the continuation of the species. Daily Life and Group Dynamics
Social groups consist of around 7 members, with 1 or 2 of them being males; however, groups may be as large as 21 individuals, still with only 1 or 2 males. The ratio of males to females is attributed to the species’ polygamous mating style. Alpha males within the troops are solely responsible for reproduction, as well as protecting the troop from any threats that may arise. Females care for the offspring, with the males having little role in rearing the young. When mature, male Javan langurs form an all-male troop until they become strong enough to compete and form a troop of their own. All-male troops rarely exhibit aggression; females are more likely to exhibit aggression toward females from other troops. |
What Does It Mean?Allogrooming:
Social grooming between members of the same species used to form bonds, reinforce social structures and family links, and build companionships. Arboreal: Physically adapted to living primarily or exclusively in trees. Cellulose: Molecule found in plant matter that gives structure and strength to the cell walls of plants and provides dietary fiber. Deciduous Forest: Forests that change seasonally. The word deciduous means to fall off at maturity. The opposite of deciduous is evergreen. Diurnal: Active during daylight hours. Mangrove: A mangrove refers to two different things: a tidal swamp ecosystem found in tropical deltas, estuaries, lagoons, or islands, and the characteristic tree species populating this ecosystem. Mangrove trees have developed unique adaptations to the harsh conditions of coastal environments. Montane forest: A forest that grows on the slope of a mountain, regardless of altitude or latitude, within a specific climate, just below the subalpine zone. Morph: A local population of a species that consists of interbreeding animals and is distinguishable from other populations by morphology or behavior, though capable of interbreeding with them. In zoology, a visual or behavioral difference between organisms of distinct populations in a species. Morphology: A branch of biology that deals with the form and structure of animals and plants. Natal group: The group into which an animal is born. Old World monkey: Monkeys native to Africa and Asia. Polygamous: Having more than one mate. Precocial: Born in an advanced state and able to feed itself almost immediately. Sacculated: Having a series of different sections (e.g., langurs have sacculated stomachs, or stomachs with three sections). Sexual dimorphism: Distinct difference in size or appearance between the sexes of an animal in addition to difference between the reproductive organs themselves. Ventrum: The stomach or belly area; the outside lower surface of the torso. |
Communication
Javan langurs communicate vocally, visually, and tactiley. They use alarm calls, similar to “ghek-ghok-ghek-ghok.” Allogrooming is an important means of social bonding, which allows the relationships between members of a troop to be strengthened. Aggression, used to establish social rank, is communicated through physical interactions, vocalizations, and visual cues. Langurs are territorial and will emit “hoots” to warn others that they are encroaching on their territory.
Javan langurs communicate vocally, visually, and tactiley. They use alarm calls, similar to “ghek-ghok-ghek-ghok.” Allogrooming is an important means of social bonding, which allows the relationships between members of a troop to be strengthened. Aggression, used to establish social rank, is communicated through physical interactions, vocalizations, and visual cues. Langurs are territorial and will emit “hoots” to warn others that they are encroaching on their territory.
Reproduction and Family
Female Javan langurs reach sexual maturity at around 3–4 years old and reproduce every 18–21 months, giving birth to one offspring at a time. The gestation period is around 170–200 days, or roughly 6–6.5 months. Babies are born precocial; that is, they are able to see and move around a short while after birth. Infants are more brightly colored than the adult members of their group. It is hypothesized that this helps the troop keep track of their young and tend to their care. Babies are cared for by all females of the group. They become independent after around 1 year. Adolescent males leave their natal group and travel alone or in bachelor groups until they are mature enough to become assume their own troop.
Female Javan langurs reach sexual maturity at around 3–4 years old and reproduce every 18–21 months, giving birth to one offspring at a time. The gestation period is around 170–200 days, or roughly 6–6.5 months. Babies are born precocial; that is, they are able to see and move around a short while after birth. Infants are more brightly colored than the adult members of their group. It is hypothesized that this helps the troop keep track of their young and tend to their care. Babies are cared for by all females of the group. They become independent after around 1 year. Adolescent males leave their natal group and travel alone or in bachelor groups until they are mature enough to become assume their own troop.
Photo credit: Fred Hsu/Creative Commons
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Fun FactsThe latin word auratus in their scientific name means “golden.” Javan langurs have no discernible mating season. |
Ecological Role
As herbivores, Javan langurs disperse seeds throughout their habitat. Through eating fruits, they help move seeds away from the parent plant, which prevents overcrowding of foliage within an area and also aids in forest growth. Through dining on leaves and dispersing seeds, they aid reforestation.
As herbivores, Javan langurs disperse seeds throughout their habitat. Through eating fruits, they help move seeds away from the parent plant, which prevents overcrowding of foliage within an area and also aids in forest growth. Through dining on leaves and dispersing seeds, they aid reforestation.
Conservation Status and Threats
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The Javan langur is listed as Vulnerable, according to the International Union for Conservation of Nature (IUCN, 2008). Their populations continue to decline, and major threats include urban development. As human populations grow, forest habitat is cut down to make room for housing, decreasing the available land for Javan langurs. Agriculture also plays a large role in their population decrease. Annual and perennial non-timber crops and small-holder farming provides income for humans, but it also places stress on the langurs' habitat. Hunting and trapping of Javan langurs for food for native populations and for pets on a local and national level also threaten the population’s health. Both of these activities are illegal, but poaching occurs regardless. The killing of adults for food decreases the wild population, as does the trapping and selling of infants for the pet trade.
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Conservation Efforts
The species is listed under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) Appendix II and has been protected by Indonesian law since 1999. Protected areas that ensure population survival include the Pangandaran Nature Reserve, Gunung Halimun National Park, and Ujung Kulon National Park, all located in Java. The Aspinall Foundation Indonesia Programme also works to preserve the native species of Java (including the langur) for the continued health of the ecosystem.
The species is listed under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) Appendix II and has been protected by Indonesian law since 1999. Protected areas that ensure population survival include the Pangandaran Nature Reserve, Gunung Halimun National Park, and Ujung Kulon National Park, all located in Java. The Aspinall Foundation Indonesia Programme also works to preserve the native species of Java (including the langur) for the continued health of the ecosystem.
References:
- https://en.wikipedia.org/wiki/Javan_lutung
- https://thewebsiteofeverything.com/animals/mammals/Primates/Cercopithecidae/Trachypithecus/Trachypithecus-auratus.html
- https://www.iucnredlist.org/species/22034/9348260#threats
- http://www.theprimata.com/trachypithecus_auratus.html
- https://animaldiversity.org/accounts/Trachypithecus_auratus/
- https://www.sciencedirect.com/science/article/pii/S187802961600250
- https://www.aspinallfoundation.org/media/1398/wild-conserv-2013-1-5-javan-langur-reinforcement-summary.pdf
- https://www.aspinallfoundation.org/the-aspinall-foundation/working-around-the-world/java/
Written by Brendan McCarthy, July 2019
