DOUC LANGURS (DOUCS): SPECIES, CHARACTERISTICS, BEHAVIOR

DOUC LANGURS

Red-shanked douc langurs

Douc langurs (Doucs) live around the Mekong River in central and southern Vietnam, central Laos and eastern Cambodia. Residing in rain forests from sea level up to elevations of 2000 meters, they have a head and body length of between 61 and 76 centimeters (24 and 30 inches) and a tail between 56 and 76 centimeters (22 and 30 inches) in length.

The douc languris one of the most strikingly colored of all monkeys, with sharply contrasting patches of color. Its head is brown and the body is mostly grey. The rump, tail and forearms are white. The upper parts of the arms, legs, hands and feet are black. Some subspecies have a bright yellow face, white whiskers and reddish chestnut upper legs.

The word "douc" (pronounced "dook") is an ancient name of Vietnamese origin. In recent years it has been found that douc langurs are actually more closesly related to proboscis monkeys and snub-nosed monkeys than to other langurs. The lifespan of douc langurs in captivity is up to 24 years. [Source: Carla Hara, Animal Diversity Web (ADW) /=]

Doucs are mainly diurnal and arboreal. It eats both leaves and fruits and hangs out in groups with 4 to 15 members. Each group is led by a single male and generally has twice as many females as males. Each sex has its own hierarchy and males are usually dominant over females. Most young are born after a 165 to 190 day gestation period in February to June when large numbers of fruit trees fruit.

Douc langurs are mostly found in tropical rainforest and monsoon forest (both primary and secondary forest) from sea level to 2000 meters (6562 feet). 1) Red-shanked douc langurs (Pygathrix namaeus nameaus) are found in north and central Vietnam, east-central Cambodia and possibly in China (on the island Hainan). 2) Black-shanked douc langurs (Pygathrix nemaeus nigripes) are found in southern Vietnam, southern Laos and eastern Cambodia. 3) Gray-Shanked Doucs (Pygathrix cinerea) occurs in the central highlands of Vietnam.

Douc Species

Red-Shanked Doucs (Pygathrix nemaeus, Linnaeus, 1771) are gray and brown in color. They live in Southeast Asia. They are 61–77 centimeters (24–30 inches) long, with a 55–77 centimeter (22–30 inch) tail. They live in the forest and eat leaves, as well as unripe frui, seeds, and flowers. They are critically endangered. Their numbers are unknown.Their population is declining. [Sources: Wikipedia]

Black-Shanked Doucs (Pygathrix nigripes, A. Milne-Edwards, 1871) are gray in color. They live in Southeast Asia. They are 60–76 centimeters (24–30 inches) long, with a 56–76 centimeter (22–30 inch) tail. They live in the forest and eat leaves, as well as seeds, fruit and flowers. They are critically endangered. Their numbers are unknown. Their population is declining.

Gray-Shanked Doucs (Pygathrix cinerea, Nadler, 1997) are gray in color. They live Southeast Asia.They are About 60 centimeters (24 inches) long, with a 59–68 centimeter (23–27 inch) tail. They live in the forest and eat leaves, as well as buds, fruit, seeds, and flowers. They are critically endangered. Their numbers are unknown. Their population is declining.

Gray-shanked langurs were first described in 1997 on the basis of newly discovered individuals in central Vietnam. These monkeys are typically found in the Central Highlands of Vietnam from Quang Nam Province in the north to Binh Dinh and Gia Lai Provinces in the south. A hybridization zone exists with red-shanked douc langurs on the northern limit of their range. Gray-shanked douc langurs live in evergreen and semi-evergreen primary rainforests usually at altitudes from 900 to 1400 meters (2950 to 4,932 feet) where the canopy cover is 80 to 95 percent and trees have a diameter at breast height of 40 to 120 centimeters and heights of 25 to 35 meters. They have also been found in some degraded forests.[Source: Matt Berger, Animal Diversity Web (ADW)]

Douc Langur Characteristics

range of red-shanked douc langurs

The head and body of douc langurs range in length from 61 to 76.2 centimeters (24 to 30 inches), 56 to 76 centimeter (22 to 30 inch) tail. Sexual Dimorphism (differences between males and females) is present: Males are larger than females. The average weight for females is 8.2 kilograms (18 pounds); for males, 10.9 kilograms (24 pounds), with their average weight being 9.7 kilograms (21.4 pounds). The young are slightly lighter in color until they reach about 10 months of age. These monkeys have a sacculated stomach, which assists them in breaking down plant cellulose and obtaining nutrition from it. Their dental formula is 2:1:2:3. [Source: Carla Hara, Animal Diversity Web (ADW) /=]

Douc langurs ares also known as "costumed apes" for their magnificent colors. Although all members of the species have gray bodies, white tails, and big pot-bellies, the three species (subspecies) can be distinguished by their different color patterns.

According to Animal Diversity Web: Red-shanked douc langurs have black hind legs with maroon "leg warmers" from knee to ankle. The forearms are white from the elbow to the wrist. The body is gray with tri-colored agouti hairs (marked with black, white and gray). The genitals of males are striking, because of the white scrotum and a penis which is bright red when erect. The perineum is white, and males have patches of white on each side of their white rump patch. These white rump patches are absent on females, allowing easy differentiation of the sexes. The faces of these langurs are also conspicuously marked, with long, white hairs on the cheeks, and reddish-yellow fur on the rest of the face. There are two bands of color over the eyes, one red above one black. /=\

Black-shanked douc langurs have all black hind legs and gray forearms. The gray fur on the chest is lighter than it is elsewhere on the body. The area of the face is colored black, and the white hairs on the cheeks are short. Above the eyes, the two bands of color are reversed from those found in red-shanked douc langurs, with the black being found over the red. The perineum is white, and males have characteristic white rump patches, but the scrotum of males is blue. /=\

Gray-shanked douc langurs have mainly gray agouti fur, although the shoulders are black, and the chest, neck, tail, perineum, face, lips, and cheeks are white. The hind feet are colored black, and the forefeet, or hands, are gray with black fingers. The facial skin is goldish-brown, and there are orange markings on the nose and in between the eyes. There is also a band of orange-black color that on the neck that blends into the black on the shoulders. The band of color above the eyes is black. /=\

The body, crown, and most of the arms of gray-shanked douc langurs are speckled light grey with a paler underside. Their shoulders, upper legs, and part of the rump are marked with white patches. The feet and hands are black while their lower legs are dark speckled grey. The bare skin on their face is yellowish brown, except for the areas around the mouth and chin which is white. Long white fur borders the sides of the face. They have an intermediate eye slant, forming a 15 degree angle from the horizontal. Their throat is white with a broad orange collar bordered by a black line which joins the black patches on their shoulders. Gray-shanked douc langur tails are nearly equal in length to their total head and body length. They are genetically similar to red-shanked douc langurs but are considered different species due to morphological differences. Compared to black-shanked douc langurs, grey-shanked douc langurs are slightly larger, but similar in size to black-shanked douc langurs. Tail length in black-shanked douc langursexceeds that of red and grey-shanked douc langurs by about 10 centimeters. Males are slightly larger than females, with an average weight of 10.9 kilograms in males and 8.2 kilograms in females. [Source: Matt Berger, Animal Diversity Web (ADW) /=]

Douc Langur Food and Eating Behavior

black-shanked douc langurs

Douc langurs are primarily herbivores (primarily eat plants or plants parts) and folivores (eat mainly leaves). They eat leaves, seeds, grains, nuts, fruit and flowers. Leaves comprise about 82 percent of their diet. Although they prefer young, tender leaves, which are more easily digested than older, tough leaves, they can still digest the tougher leaves with their sacculated stomach (a stomach with multiple bag-like structures that help digest tough vegetation), which helps them to break down cellulose. [Source: Carla Hara, Animal Diversity Web (ADW) /=]

Doucs are very particular when foraging for food. Leaves and fruits are picked and eaten only after close inspection. If leaves are old or fruit is either ripe or overripe it is then discarded. Unnripe fruits and their seeds comprising 14 percent of their diet, and flowers male up 4 percent of their diet. Douc langurs don't drink water; they obtain all the water they need from the food they eat.

Among the plants and plant parts that are eaten are: Garcilinia multiflora leaves, Garcilinia mangostana leaves, Ficus vasculosa leaves, Ficus chrysocarpa leaves, Teonogia tonkinensis leaves, Bacaurea sapida leaves, Allospondias lakonensis leaves, Canarium album leaves, Polyalthia nemosalic leaves, Chisocheton paniculatus leaves, Musa coccinea leaves, Castanea mollissma fruits, Castanopsis boisii fruits, Madhuca pasquieri fruits, Ficus vasculosa fruits, Ficus hispida fruits, Tenongia tonkinensis fruits, Broussonetia papyrifera fruits, Bacaurea sapida fruits, Allospondias lakonenis fruits, Grewia paniculata fruits, Peltoforum tonkinense flowers, Adenantheria microsperma flowers, Garcilinia oblongifolia shoots, Bambusa spinosa shoots, Garcilinia multiflora buds, Garcilinia oblongifolia buds and Ficus hispa buds. /=\

Douc Langur Behavior

Douc langurs are arboreal (live mainly in trees), diurnal (active mainly during the daytime), motile (move around as opposed to being stationary), nomadic (move from place to place, generally within a well-defined range), social (associates with others of its species; forms social groups), and have dominance hierarchies (ranking systems or pecking orders among members of a long-term social group, where dominance status affects access to resources or mates). In terms of home range, The home range size for these primates in the wild has not been described. [Source: Carla Hara, Animal Diversity Web (ADW) /=]

Douc langursare usually found in groups of four to 15, but has been found in groups with 30 to 50 individuals. Occasionally, single individuals of either sex are seen in the forest. Social groups contain one or more adult males and about twice as many females. Each sex seems to have its own dominance hierarchy, and males are dominant over females. When they near maturity, both males and females disperse from their natal groups.

Douc langurs move quadrupedally (on all fours), although they often jump from place to place. When jumping, these monkeys push off of a support using their hind limbs, and extend their arms in front and above them. They usually land on their feet. They are reported to move through the forest canopy along established pathways. /=\

gray-shanked douc langurs

Douc langurs are playful animals, with juveniles tending to play more than adults. Social play is always accompanied by a grimmace-like "play face," and consists of climbing, jumping, running, hanging and swinging, while touching, pulling, mouthing, wrestling, and chasing a partner. The most active play times are in late morning, early afternoon, and just before bedding down. In captivity, aggressive interactions are rare. Like other primates, douc langurs groom one another, and have been observed sharing food in captivity.

Gray-shanked douc langurs move by jumping and brachiating (using the arms to swing from branch to branch). They sometimes use a suspensory posture (hanging below the branches) while eating leaves from small tree branches. Gray-shanked douc langurs live in small, social groups of four to 15 individuals and a female to male ratio of two to one. They have also been seen alone and in large groups of up to 50. Males are the dominant sex and dominance hierarchy have been observed in captivity. Social interactions are complex, ranging from aggression to playing. [Source: Matt Berger, Animal Diversity Web (ADW)]

Douc Langur Communication

Douc langurs communicate with vision, touch and sound and sense using vision, touch, sound and chemicals usually detected with smell. They are highly social and therefore have a great variety of communication patterns, sharing visual, tactile, and accoustic information. [Source: Carla Hara, Animal Diversity Web(ADW) /=]

Carla Hara wrote in Animal Diversity Web: Like many other primates, doucs have a specific "play face" that they display with their mouth open and their teeth partially showing. A grimace with their teeth showing is used to initiate grooming or play. A stare, with raised-eyebrows is used as a threat, and is often responded to with a submissive grimmace. A jaw-thrusting/head shaking face is used to initiate sexual interactions, and presenting is used when a female wishes to engage in copulation. /=\

A low-pitched growl is made to threaten other members of the group. Loud barks and quickly moving around the trees while hitting branches with both their hands and feet can be a sign of threat. This call can also occur during feeding . A squeal is often heard during agonistic encounters. A faint, bird-like call, called a twitter, is often used in response to a stare or before social grooming, and is thought to be a submissive signal, allowing another animal to approach without fear of an aggressive response . /=\

range of the gray-shanked douc langur

The main tactile communication channels are social grooming and play. In social grooming, parasites, dandruff flakes and other junk is removed from another monkey's fur with the hands and mouth. Females are the most active groomers, grooming each other, infants and juveniles, and adult males. Grooming is thought to reinforce social bonds between individuals. During play, these monkeys may wrestle, hit, chase, touch, pull on, and mouth one another. /=\

Among Gray-shanked douc langurs, Matt Berger wrote in Animal Diversity Web, growls can be used as warnings or threats to the other members of the group. Twitters are softer sounds emitted when the animal is being submissive. Tactile communication includes grooming and sparring. The purpose of grooming is to remove parasites and strengthen bonds between group members. In groups with more than one male, females are more likely to groom males. Grooming often occurs just before resting for the night. Sparring is an aggressive behavior and involves slapping, pulling, and grabbing. Visual forms of communication include a variety of postures and facial expressions such as play face, grimace, stare, and a sexual display. Play face is used in play with another member. A grimace is observed as part of submissive behavior towards another member. The stare conveys curiosity or aggression. The sexual display is when the female presents herself to a male signaling that she is ready to copulate or a male signaling to a female by facial movements that he is ready to copulate. [Source: Matt Berger, Animal Diversity Web (ADW)]

Douc Langur Mating, Reproduction and Offspring

Douc langurs are polygynous (males have more than one female as a mate at one time). Female menstrual cycles are approximately 28 to 30 days. During estrous, the perineum of the female becomes swollen and red. Douc langurs engage in seasonal breeding. The breeding season is from August to December, with births following between February and June. The number of offspring is usually one. The interbirth interval of these monkeys has not been reported. Captive females have an interbirth interval around two years. Females reach sexual or reproductive maturity at four to five years and males do so at four to five years. [Source: Carla Hara, Animal Diversity Web (ADW) /=]

According to Animal Diversity Web: Right before mating, both the male and female give each other sexual signals. Males and females both conduct the following display, directed at members of the opposite sex: They drop their jaw forward, lift their eyebrows up then down, then shake their head. The female makes the first move, and has always been observed to initiate the copulation. She lies down on a branch and eyes her chosen mate by looking over her shoulder, a position called "presenting." The male gives a stare back then aproach the female and give a signal if he would like to move some place else to mate or stay where she has chosen. Not all times that a female presents to the male are followed by copulation. Both single and multiple matings have been reported. /=\

The gestation period ranges from 165 to 190 days. During pregnancy the perineum remains swollen and red. In the wild, births peak between February and June when the fruit is plentiful. During birth, females often touch their vagina, and move between squatting and stretching positions. Females help the baby to emerge by pulling on it. The infant, in turn, helps to deliver itself by pulling on the mother's fur once its arms are free. After birth, the infant is licked clean, but in captivity, there has been no observed consumption of the afterbirth.

The baby clings to its mother from the minute it is born. Infants are typically carried on the mother's belly. Females nurse their infant from both nipples. An orphaned infant was observed being fed by two females in the group and also cared for by a male. No information is available on the duration of nursing.

Gray-Shanked Douc Langur Mating, Reproduction and Offspring

Among Gray-shanked douc langurs, Matt Berger wrote in Animal Diversity Web: Courtship is initiated with a visual display in which members of the opposite sex thrust their jaw forward and shake the head sideways with small jerky movements. The eyebrows are raised and lowered several times and the upper eyelids are momentarily lowered. Copulation occurs after the other individual gives the same response to this display. The display may be repeated until the female presents herself for mating. Presenting is where the female flexes all four limbs and presses her belly against the substrate. The base of the tail is raised slightly with the head completely raised. The perineum is pointed towards the male. [Source: Matt Berger, Animal Diversity Web (ADW)]

All copulations are preceded by presenting but not every presenting sequence leads to copulation. Copulation begins when the male mounts by positioning the hands on the hips of the female. The male then leans over to the point which the ventral surface is in contact with the female’s dorsal surface. After firmly pressing the feet on the substrate, the male begins to thrust. The process is typically a single mount although double mount sequences have been observed.

Gray-shanked douc langurs have two-lobed hemochorial placentas with one lobe anterior and the other posterior. Gray-shanked douc langurs give birth seasonally, with births peaking between January and August during the fruiting season. Newborns have been recorded with weights between 500 and 720 grams.

Douc Langurs, Humans and Conservation

Red-shanked doucs, black-shanked doucs, and gray-shanked doucs are all listed as critically endangered. Their numbers are unknown. Their populations are declining. On the International Union for Conservation of Nature (IUCN) Red List Douc Langurs are listed as Critically Endangered. On the US Federal List they are classified as Critically Endangered. In CITES (Convention on International Trade in Endangered Species of Wild) they are in Appendix I, which lists species that are the most endangered among CITES-listed animals and plants. [Source: Carla Hara, Animal Diversity Web (ADW) /=]

The decline in douc langurs is due primarily to hunting by humans, deforestation and other disruptions to their habitats. Some langurs are collected for the pet and medicine trades, and some are hunted for food and for sport. The forest habitat occupied by this species experienced intense disruption during the Vietnam war. In areas of Vietnam where defoliants were used during the war, reproduction of douc langur has suffered. /=\

Gray-shanked douc langurs are one of the primates named in "Primates in Peril: The World’s 25 Most Endangered Primates." It is estimated that there are only about 700 individuals left. Matt Berger wrote in Animal Diversity Web: Gray-shanked douc langurs are used for food, traditional medicine, and in pet trade. However, these monkeys are critically endangered and these activities are illegal in most areas. The main predators of gray-shanked douc langurs are humans. This species is hunted by humans and their habitat is destroyed for logging and agriculture. Gray-shanked douc langurs have also been observed responding to hunters by hiding in the trees instead of fleeing, which can make them an easy target for skilled hunters. Natural predators have not been reported, but are likely to be large raptors or southeast Asian cat species. [Source: Matt Berger, Animal Diversity Web (ADW)]

Image Sources: Wikimedia Commons

Text Sources: Animal Diversity Web animaldiversity.org ; National Geographic, Live Science, Natural History magazine, David Attenborough books, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Discover magazine, The New Yorker, Time, Reuters, Associated Press, AFP, Lonely Planet Guides, Wikipedia, The Guardian, Top Secret Animal Attack Files website and various books and other publications.

Last updated December 2024