LANGURS: TYPES, GENUSES, LEAF MONKEYS, BEHAVIOR

LANGURS

Langurs are mostly leaf-eating, tree-residing, forest-dwelling monkeys. They are regarded as among the most arboreal of all Old World monkeys. They are active throughout the tree canopy and can be found in both primary and secondary forests. They rarely come to the ground. When they do it is mainly to gain access to mineral sources.

Leaf monkeys and langurs are in the subfamily Colobinae, which is part of the family Cercopithecidae (Old World monkey), which has a wide geographical distribution throughout Asia and Africa. Leaf monkeys and langurs are scattered over a wide area in India, Southeast Asia and Indonesia. They are mainly diurnal (active during the day). They eat crops as well as leaves and and some prefer fruit and flowers and may migrate a great distance to gain access to fruit. Some species never descend from trees except to get water during the middle of the dry season.

The Colobinae subfamily of the Old World monkey family includes 61 species in 11 genera, including the black-and-white colobus of Africa, the large-nosed proboscis monkey of Borneo, and the gray langurs of South Asia India. Some classifications split the colobine monkeys into two tribes, while others split them into three groups. Both classifications put the three African genera Colobus, Piliocolobus, and Procolobus in one group. The various Asian genera are placed into another one or two groups. [Source: Wikipedia]

The main Southeast Asian groups are:
A) Tribe: Presbytini: 1) Langur (leaf monkey) group; 2) Genus Trachypithecus - lutungs; 3) Genus Presbytis - surilis; 4) Genus Semnopithecus - gray langurs
B) Odd-nosed group: 1) Genus Pygathrix - doucs; 2) Genus Rhinopithecus - snub-nosed monkeys; 3) Genus Nasalis - proboscis monkey; and 4) Genus Simias - pig-tailed langur

Websites and Resources: Animal Diversity Web animaldiversity.org ; BBC Earth bbcearth.com; A-Z-Animals.com a-z-animals.com; Live Science Animals livescience.com; Animal Info animalinfo.org ; World Wildlife Fund (WWF) worldwildlife.org the world’s largest independent conservation body; National Geographic National Geographic ; Endangered Animals (IUCN Red List of Threatened Species) iucnredlist.org

Langur Characteristics

Most langurs are grayish, brownish or blackish, with paler underparts. Some have light colored markings on their head or stripes on their thighs. Many species have white, yellowish or black markings on their head, rump, limbs and tail. Some have white circles around their eyes. Others have a pointed crest on the top of their heads.

Langur adults weigh from five to eight kilograms and have a head and body length of 42 to 61 centimeters (16.5 to 24 inches) and a tail length of 50 to 85 centimeters (20 to 33.5 inches) . Most langurs are leaf-eating monkeys and have a sacculated stomach made up of different compartments that help to break down the cellulose in the leaves and obtain the maximum possible nutrition from innutritious leaves. The stomachs of monkeys in the Colobinae subfamily to which langurs belong are large and multi-chambered. The forestomach hosts bacteria with cellulose-digesting abilities, allowing these mammals to process leaves and plant fibers.

Langur bodies are adapted for tree life. They have long tails, a slender body, strong slender hands, and well developed fingers. Although langurs eat leaves their primary sources of nutrition come from fruits and seeds. On a daily basis they range through the forest between 500 and 800 meters to forage.

Langur Behavior

Langur groups tend to be small, with around 7 to 15 members, including a dominate male and three or more females and their young. In some cases you can find monogamous pairs. A typical group embraces a territory of 35 to 40 hectares. Males not in a group may form all male groups. Many langur and Asian colobine monkeys form territorial groups of related females (natal groups) who appear to safeguard availability to resources and allow preferential access to a single male, but usually for no more than two years.

Many langurs engage in alloparental care (alloparenting), the act of caring for young that are not one's own direct offspring. According to Animal Diversity Web: It is hypothesized that alloparental care provides time and freedom for mothers to forage, improves parenting skills of the alloparent, and ensures the social integration of new infants to the group increasing the likelihood of adoption if the mother is killed. Additionally, it has been suggested that the infrequent but sometimes abusive handling of new infants by the alloparent reduces resource competition for the alloparents’ own offspring. [Source: Lauren Ris, Animal Diversity Web (ADW)]

Dominate male changes are followed by bouts of infanticide in which the new male methodically kills all unweaned infants in the group and mates with females ensure their offspring carry his genes not those of his rival. This behavior was first noted among Hanuman langurs but occurs among other species as well. Curiously, many langur infants are born with an orange natal coat that contrasts with that of other monkey changes to adult coloration after a few months. This feature would seem to help new males target their victims.

Langurs make a noise that sounds like a "staccato cough" when they are angry or spot a tiger. When langurs drink at water holes, there is often a scout in a tree that keeps an eyes for tigers and other predators.

Gray Langurs of South Asia (Semnopithecus Genus)

dusky leaf monkey

Semnopithecus is a genus of Old World monkeys native to the Indian subcontinent, with all species except for two being commonly known as gray langurs. Members of this genus tend to spend as much time on the ground as in the trees and inhabit forest, lightly wooded habitats, and urban areas. Mostly walk quadrupedally (on all fours) and make occasional bipedal hops, climbing and descending supports with the body upright, and leaps. Langurs can leap 3.6–4.7 meters (12 to 15 feet) horizontally and 10.7–12.2 meters (35–40 feet) in a descending direction. Most species are found at low to moderate altitudes, with the exception of the Nepal gray langur and Kashmir gray langur which can be found up to 4,000 meters (13,000 feet) in the Himalayas. [Source: Wikipedia]

Gray langurs are largely gray but some are more yellowish, with a black face and ears. As a rule, species can be differentiated by the darkness of their hands and feet, their overall color and the presence or absence of a crest. Generally, northern Indian gray langurs have their tail tips looping towards their head during a casual walk whereas southers Indian and Sri Lankan gray langurs have an inverted "U" shape or a "S" tail carriage pattern. There are also significant variations in the size depending on the sex, with the male always larger than the female. The head-and-body length ranges from 51 to 79 centimeters (20 to 31 inches), with tails, ranging from 69 to 102 centimeters (27 to 40 inches) and always longer than their bodies. Langurs from the southern part of their range are smaller than those from the north. The average weight of gray langurs is 18 kilograms (40 pounds) in the males and 11 kilograms (24 pounds) in the females. The larger gray langurs among the largest species of monkey found in Asia.

Gray langurs are diurnal. They sleep during the night in trees but also on man-made structures like towers and electric poles when in human settlements.When resting in trees, they generally prefer the highest branches. Gray langurs are primarily herbivores. However, unlike some other colobines they do not depend on leaves and leaf buds, but also eat coniferous needles and cones, fruits and fruit buds, shoots, roots, seeds, grass, bamboo, fern rhizomes, mosses, and lichens. Leaves of trees and shrubs are their most preferred food, followed by herbs and grasses. Non-plant material consumed include spider webs, termite mounds and insect larvae. They forage on agricultural crops and other human foods, and even handouts. Although they occasionally drink, langurs get most of their water from the moisture in their food.

Gray Langurs Behavior

Gray langurs exist in three types of groups: 1) one-male groups, comprising one adult male, several females and offspring; 2) multiple-male groups, comprising males and females of all ages; and 3) all-male groups. All-male groups tend to be the smallest of the groups and can consist of adults, subadults, and juveniles. Some populations have only multiple-male groups as mixed sex groups, while others have only one-male groups as mixed sexed groups. Some evidence suggests multiple-male groups are temporary and exist only after a takeover, and subsequently split into one-male and all-male groups. [Source: Wikipedia]

Social hierarchies can be found in all group types. In all-male groups, dominance is attained through aggression and mating success. With sexually mature females, rank is based on physical condition and age. The younger the female, the higher the rank. Dominance rituals are most common among high-ranking langurs. Females within a group are matrilineally related. Female memberships are also stable, but less so in larger groups. Relationships between the females tend to be friendly. They will do various activities with each together, such as foraging, traveling and resting. They will also groom each other regardless of their rank. However, higher-ranking females give out and receive grooming the most

Javan langur

In one-male groups, the resident male is usually the sole breeder of the females and sires all the young. In multiple-male groups, the highest-ranking male fathers most of the offspring, followed by the next-ranking males and even outside males will father young. Higher-ranking females are more reproductively successful than lower-ranking ones. Female gray langurs do not make it obvious that they are in estrous. However, males are still somehow able to deduce the reproduction state of females. The gestation period of gray langur lasts around 200 days. A single offspring is usually born. Infanticide is common among gray langurs.

Gray langurs make a number of vocalizations. The include: 1) loud calls or whoops made only by adult males during displays; 2) harsh barks made by adult and subadult males when surprised by a predator; 3) cough barks made by adults and subadults during group movements; 4) grunt barks made mostly by adult males during group movements and agonistic interactions; 5) rumble screams made in agonistic interactions; 6) pant barks made with loud calls when groups are interacting; 7) grunts made in many different situations, usually in agonistic ones; 8) honks made by adult males when groups are interacting; 9) rumbles made during approaches, embraces, and mounts; 10) hiccups made by most members of a group when they find another group.

Langurs of Southeast Asia (Trachypithecus Genus)

Most langurs and leaf monkeys in Southeast Asiain Southeast Asia, belong to the genus Trachypithecus. Trachypithecus is a genus of Old World monkeys containing species known as lutungs, langurs, or leaf monkeys. They range across much of Southeast Asia from northeast India to southern China, Borneo into Indonesia, and are found in Vietnam, Myanmar (Burma) Thailand, Java, and Bali). [Source: Wikipedia +]

Trachypithecus was recognized as a separate genus by Eudey in 1987, but occasionally it is still considered a subgenus or synonym of Presbytis or of Semnopithecus. Among the species recognized in the genus are: François’ langurs (Trachypithecus francoisi) Trachypithecus vetulus, T. johnii, T. geei, T. pileatus, T. phayrei, T. cristatus, T. auratus, and T. obscurus. There is some debate over whether Trachypithecus leucoscephalus is a subspecies of François’ langur or a distinct species. Recent DNA research suggests that it may be distinct. [Source: Lauren Ris, Animal Diversity Web (ADW)]

Langurs and leaf monkeys in the Trachypithecus genus have a slim body with a long tail. Their fur varies in color, depending on the species, from black and grey to orange yellow. Many species have skin markings and a brighter lower surface. The hair on their head is often compared to a hood. Their arms are very short in comparison to the feet and their thumbs are also somewhat shorter. The inner surfaces of the hands and feet are hairless so that their fur does not get caught when reaching into branches. These monkeys range in length from of 40 to 80 centimeters and weigh from five to 15 kilogramss, with males generally being larger than females. A bulge over the eyes and other details, primarily in the head, differentiate it from the surilis. +

Christine Bedore wrote in Animal Diversity Web: Colobines have a long tail, and dense fur. Also common to colobines is an under-bite in which the lower jaw projects out further than the upper jaw. The genus Trachypithecus is distinguished from other colobines by its prominent nasal bones, a well-developed coronal crest, and poorly developed brow ridges. There is also a reduction in the size of the first digit (thumb) facilitating the brachiating (using the arms to swing from branch to branch) movements they utilize. The fore and hind limbs are more equal in length than most other cercopithecid (Old World monkey)s (Old World monkeys), or Old World Monkeys, suggesting that the group previously occupied a more terrestrial habitat. [Source: Christine Bedore, Animal Diversity Web (ADW)]

Behavior of Trachypithecus Langurs

dusky leaf monkey

Langurs and leaf monkeys in the Trachypithecus genus live in forests, often preferring rain forests, although occasionally they are also found in secluded mountain forests. They spend the largest part of the day in the trees, where they crawl along the branches on all fours, although they can also jump well from tree to tree. They are diurnal, although more active in the early mornings and the afternoon. They are primarily eat leaves, fruits, and buds. To digest the tough leaves, they developed a multichambered stomach. +

Langurs and leaf monkeys in the Trachypithecus genus live in groups of five to 20 animals, mostly in harems, i.e. a single male with several females. Young males leave their birth group when fully mature, often forming bachelor groups. If a new male takes over a harem, defeating and scaring off the harem leader, he often kills the children of the group. Langurs and leaf monkeys in the Trachypithecus genus are territorial, with loud shouting to defend their territories from other langurs and leaf monkeys, resorting to force if the outsiders are not scared off. They have a common repertoire of sounds with which they warn group members. Also, mutual grooming plays an important role. +

Usually a single offspring is born after a seven-month gestation period. Newborns usually have a golden-yellow fur. The mother shares responsibilities of rearing the young with the other females ("aunties") of the harem. They hand the young around, play with it, carry it, and cuddle it, while the mother searches for food. If the mother dies, another female adopts the young animal. Young are weaned in the latter half of their first year, and reach full maturity at 4 to 5 years. The life expectancy is estimated at 20 years. +

Presbytis Genus Langurs of Sumatra, Borneo, Java and Malaysia

Presbytis is a genus of Old World monkeys also known as langurs, leaf monkeys, or surilis native to Sumatra, Borneo, Java and smaller nearby islands in Indonesia and the the Thai-Malay Peninsula. They are smallish, slimly built primates. Their fur at the top is brown, grey, black, or orange, and at the lower surface whitish or greyish, sometimes also orange, with some species having fur designs at the head or at the hips. Their German name of Mützenlanguren ("capped langurs") comes from the hair on their head, which forms a tuft. Surilis range in adult length from 40 to 60 centimeters (with a 50- to 85-centimeter-long tail) and a weight of five to eight kilograms. [Source: Wikipedia]

Langurs of the Presbytis Genus differ from the other langurs: 1) in head shape (particularly the poorly developed or absent brow ridges, and the prominent nasal bones), 2) in the teeth, and 3) by the size of their small thumbs. Two other genera, Trachypithecus and Semnopithecus, were formerly considered subgenera of Presbytis. The species-level taxonomy of Presbytis is complex, and significant changes have been proposed for several in recent years.

Diurnal forest dwellers, Langurs of the Presbytis Genus mainly eat leaves, fruits, and seeds and spend nearly their entire lives in the trees. They live in groups of up to 21 animals (typically 10 or fewer animals in most species) consisting of a male, several females, and their young. A few species have been observed in monogamous pairs. Lone males and all-male groups have also been observed. The groups have a hierarchical arrangement, with intergroup communication that is both vocal and postural. Their gestation period is five to six 5–6 months, producing a single offspring. Newborns are white colored and have a black strip at the back, although some have a cross-shaped mark. By one year old, the young are weaned and at an age of 4–5 years, they are fully mature. The typical life expectancy in the wild remains poorly known for most species, but captive Sumatran surilis have lived more than 18 years.

Doucs (Douc Langurs)

douc langur

The doucs or douc langurs comprise the genus Pygathrix. They are colobine Old World monkeys, native to Southeast Asia, mostly Vietnam. There are three species: red-shanked douc, black-shanked douc, and gray-shanked douc. Even though they are known as "douc langurs", they are in fact more closely related to the proboscis monkey and snub-nosed monkeys than to any of the langurs. [Source: Wikipedia]

Doucs have distinct appearances. The red-shanked douc has bright maroon legs and reddish patches around the eyes. The grey-shanked douc is less colorful and has speckled grey legs and orange markings on the face. Both have dappled grey bodies, black hands and feet and white cheeks, although the cheek hairs of the red-shanked douc are much longer. The black-shanked douc has black legs.

Doucs have long long hind limbs and tail that allows them to be very agile in trees where they spend the vast majority of their time. They live in small family groups headed by one adult male. A single group may have several adult females, and many children. Young males without a family group often make their own troops. Females usually bear a single offspring, which is nursed for about a year.

Endangered Langurs

Some langur species are threatened. Delacour’s langur (T. f.delacouri) of central Viet Nam is critically endangered. It may be the most endangered monkey in Asia with fewer than 250 individuals. It has also been reported that the white-headed langur (T. f. leucocephalus_ in southeastern China has a population of only about 400, a result of hunting the monkey for its believed medicinal value. Populations of most other species of Trachypithecus are also declining due to loss of habitat. The douc langur and Francois langur are endangered.

Many species are suffering from the effects of logging, deforestation, hunting and loss of habitat. In many cases, suitable habitat are only fragments of what they once were. Their numbers have declined by more than half in last couple of decades.

In south India, the meat of the Nilgiri langur is believed to be an aphrodisiac and have other medicinal qualities. In Thailand, the blood of Phayre’s langur and other leaf monkeys believed to make the drinker strong and virile especially when mixed with local whiskey.

Popa Langur — Just Discovered But ''Already Facing Extinction''

The Popa langur, named after its home on Mount Popa in Myanmar, is critically endangered with only 200 to 250 individuals remaining. First designated as a species in 2020, they are known for their distinctive spectacle-like eye patches and greyish-coloured fur. They live in four isolated populations. About 100 of the monkeys live in a protected forest near Mount Popa. Already it is in danger of extinction due to habitat loss and hunting. [Source: Helen Briggs, BBC, November 11, 2020]

Helen Briggs of the BBC wrote: “Scientists have long suspected there might be a new species in Myanmar, based on DNA extracted from the droppings of wild monkeys, but evidence has been hard to find. With very little information to go on, they turned to historical specimens stored in natural history museums in London, Leiden, New York and Singapore. Early explorers to Myanmar collected the monkey specimens, which had never been examined in detail.

“The researchers extracted DNA and measured physical features such as tail and ear length, which they compared with those of wild populations. This revealed a new species, the Popa langur, which is found only in patches of forest in the centre of the country. Most live in a wildlife sanctuary park on the slopes of the sacred pilgrimage site of Mount Popa.

“Describing the species scientifically will help in its conservation, said Frank Momberg of the conservation group Fauna & Flora International. He told BBC News: "The Popa langur, just newly described, is already critically endangered and facing extinction so it's absolutely critical to protect the remaining population and to engage with local communities as well as private sector stakeholders to safeguard its future."

The discovery was described in the journal Zoological Research. Genetic studies revealed that the Popa langur (Trachypithecus popa) separated from other known species around one million years ago. Christian Roos of the primate genetics laboratory at the German Primate Centre in Gottingnen said the animals faced threats from habitat loss and hunting. “Hunting is a big problem but the bigger threat is the habitat is almost gone and it is reduced, fragmented and isolated due to human encroachment, " he said.

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Last updated December 2024