Langurs are 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.
Most langurs are grayish, brownish or blackish, with paler underparts. Some have light colored markings on their head or stripes on their thighs. Langur adults weigh from five to eight kilograms and have a head and body length of 42 to 61 centimeters and a tail length of 50 to 85 centimeters.
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 the 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 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.
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.
Some langur species are threatened. Delacour’s langur is critically endangered. 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.
The Hanuman langur lives in India, Bangladesh, Sri Lanka, southern Tibet, Nepal, Sikkim, northern Pakistan and Kashmir. Named after the Hindu monkey god, it has adapted to a number of environments: rain forests, desert edges, mountains and alpine scrub, from sea level up to elevations of 4000 meters. They have a head and body length of between 41 and 78 centimeters and a tail between 69 and 108 centimeters in length and weigh between 5.4 and 23.6 kilograms. Some live to be more than 40 years old.
The upper parts of Hanuman langur’s body and head are mostly brown, grey or buff. The crown and lower parts are white, orange-white or yellowish. Even though it is quite at home in the trees and can leap horizontally 15 meters and jump vertically 5 meters, it spends much of its time on the ground. Its most distinctive call is a booming morning whoop that apparently helps to define the space occupied by different groups. Their long tails helps them balance on cliffs, where they sometimes hang ouyt
The Hanuman langur is mainly diurnal and is most active in the mornings and evenings. It eats mostly leaves but also consumes fruits, flowers and cultivated crops. In India, there are about 100,000 of them. There are also significant numbers of them in Sri Lanka.
Hanuman Langur Group Behavior
Hanuman langurs hangs out in groups with 13 to 37 members. Each group is led by a single male and generally has twice as many females as males. Males often work out their rank by fighting. Most young are born after a 190 to 210 day gestation period in the dry season. Weaning is done after 10 to 12 months. Females reach sexual maturity when they are three to four; males, when they are six to seven.
Sometimes an all-male group will attack mixed-sex groups. If the dominant male is defeated sometimes the new leader will kill all the infants. This measure will bring the females into estrus within a couple weeks and allow the new leader to mate and father new offspring.
Females often share babysitting duties within a close-knit group of females and their offspring. The young are born with dark fur than turns thick and greyish gold after a few months. More than half are killed by disease, predators or infanticide---a common practice when a new male takes over a langur group.
Hanuman Langurs and Humans
Jennifer S. Holland wrote in National Geographic, “In India monkey business takes on a whole new meaning. Hanuman langurs are trained in New Delhi to scare off aggressive rhesus monkeys and other wild animals that might roam into public spaces and cause mischief. When the city hosted the 2010 Commonwealth Games... its municipal council used 38 langurs to help with critter control. These primates are valued as more than security guards. Hindus revere them as a symbol of the monkey deity Hanuman, whose simian army helped rescue Sita, the god Rama's wife, from a demon king, according to a Sanskrit epic. Langurs' black faces and extremities call to mind the burns that Hanuman suffered in the course of his heroism. [Source: Jennifer S. Holland, National Geographic, August 2011]
The lifestyle of the monkeys reflects this state of grace. In the city of Jodhpur, at the edge of the Thar, or Great Indian, Desert, some 2,100 wild langurs regularly leap into human society to sample its goods. Local Hindus share picnics in parks and turn shrines into buffets of offerings for the monkeys. Some let the holy beasts glean from their gardens. That's a nice change of pace from life in the Thar, where sizzling heat and scant moisture make survival a challenge, and the monkeys must scrounge for plants and occasional insects to eat. Since most langurs are tree dwellers, these often scamper high on the desert cliffs or perch on nearby rooftops. But the human population is growing fast in the region these days, and people may be tempted to retaliate if the monkeys' garden incursions turn into full-fledged crop raids. Even animals this beloved could wear out their welcome.
A number of Hanuman langurs reside t Mandor Garden on the outskirts where they are often seen munching on picnic snacks, which are sometimes given to them and sometimes snatched. In the That Desret temperatures sometimes reach 120 degrees.
Using Langurs to Control Rhesus Monkeys
Animal control officials often use langurs, which are bigger and fiercer monkeys, to scare away the smaller macaques or drive them into cages. Julian West wrote in The Telegraph: “The Indian government has put several large monkeys on its payroll in a last-ditch attempt to scare away thousands of smaller rhesus monkeys that have been attacking New Delhi's civil servants, sabotaging hotlines and stealing state secrets. The fearsome-looking langur monkeys now patrol South Block, the magnificent red sandstone complex that houses the defence, external affairs and finance ministries - as well as the army headquarters and Delhi's main hospital - snarling menacingly at intruders. Each receives a salary of 600 rupees (£10) a month, paid in bananas. [Source: Julian West, The Telegraph, April 15, 2001]
“The staff at President's House, Lutyens's splendid monument to the raj which adjoins South Block, devised the novel plan of using langur patrols after monkeys were found peering into President Narayan's private quarters and romping over his verandah. The langurs, which are extremely ferocious and attack other monkeys on sight, make their rounds each morning before the civil servants arrive with their tempting tiffin-carriers, or lunch-boxes. However, as temporary employees, unlike the horses, dogs and mules employed by the government, they have not been given the customary Indian civil service numbers. Unfortunately, though, South Block's cheeky monkeys have decamped to New Delhi's main post office. The city's residents, who are already accustomed to losing large quantities of their mail through pilfering, have resigned themselves to yet more monkey business. [Ibid]
The douc langur lives 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, it has a head and body length of between 61 and 76 centimeters and a tail between 56 and 76 centimeters in length.
The douc langur is 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 douc langur is 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.
There are nine species of brown-ridged langur. They are scattered over a wide area in India, Southeast Asia and Indonesia. Residing mainly in forests, they have a head and body length of between 40 and 76 centimeters and a tail between 57 and 110 centimeters in length and weigh between 4.2 and 14 kilograms
Brown-ridged langurs are usually brown, dark grey or black. Most 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.
Brown-ridged langurs are mainly diurnal and arboreal. They eat leaves and crops but prefer fruit and flowers and often 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.
Brown-ridged langur groups tend to be small with 6 to 30 members. Each group is led by a single male and generally has twice as many females as males. Males periodically fight for dominance of a group. When a new male takes over a group he often kills all the young. Females have their own hierarchy system. Most young are born after a 140 to 200 day gestation period.
White Headed Langur
The white-headed langur is a monkey that lives in an area of karst mountains in Guanxi Province. Adults are black with white heads and black faces. Infants are yellow. Infanticide---in which a male takes over a group and kills all the newborns presumably so females can start ovulating and bear the male’s offspring---is practiced.
The population of white-headed langur dropped from around 2,000 individuals in the late 1980s to fewer than 500 in the mid 1990s due mainly to poaching by non-locals to supply wildlife food market. Since then their numbers have increased mainly by encouraging local villagers to help the monkeys by preserving the forest where they live and driving away poachers. Conservationists achieved these gains by providing clean water to the villagers to earn their trust and cooperation and building biogas convertors to keep them from cutting down trees. The programs has been so successful it has been held up as a model for saving endangered animals in other localities.
Pan Wenshi, a conservationist known for his work with pandas, has been the leader in the drive to save the langurs. He helped set up a 24-square-kilometer nature reserve where most the langurs live and initiated the programs to get villager involved in saving them.
Proboscis monkeys are named for their long bulbous noses. They are found in forests along rivers and in swamps and coastal lowlands of Borneo. Indonesians call them "Belanda," which means "white man."[Source: Tim Laman, National Geographic, August 2002]
About 8,000 proboscis monkeys are estimated o be living in the wild. They need relatively large areas to live in to collected all the food need. Proboscis monkeys have had their numbers reduced by poaching and loss of habitat resulting from clearing of the rain forest. Particularly damaging for them has been the drainage of swamps and shrimp farming in coastal habitats.
Proboscis monkeys are one of Asia’s largest monkeys. Adult males can reach lengths of two feet, excluding their tail, and weigh 50 pounds. Females are about half the size. They have long tails which are not used for gripping but may provide balance when then the monkeys fly through the air. They also have very long limbs, ideal for swinging in branches and moving from tree to tree. Infants have dark fur and bluish faces. Twins are rare.
Males have the largest noses. They are long, bulbous and drop downward below the chin. When males grunt their nose jerk upwards. Female noses are significantly smaller and turned up and look like the noses on clowns. Youngsters have short, turned-up button nose. The large male noses are believed to be help them attract females and possible dissipate excess heat.
Proboscis monkeys are great leapers. They can leap great distances from one branch to branch and tree to tree. They push off with their powerful hind legs and fly through the air with their arms extended over their heads, ready to grasp a branch. Mothers leap with their offspring clinging to their stomachs.
Proboscis monkeys have chamber stomachs like ruminants such as cows. They eat large quantities of leaves and rely on bacteria in their stomachs to break down the cellulose in the leaves. These monkeys often spend several hours eating and several hours relaxing while food in their stomachs digests.
Proboscis monkeys eat seeds and green fruits as well as leaves. The have a permanent pot belly, which encloses a large chambered stomach necessary to process all the fibrous food they eat. They avoid sweet fruits which could cause deadly bloating from rapid fermentation. Male proboscis monkeys sometimes move their noses out of the way when they eat.
Studies by Elizabeth Bennett and Carey Yeager,
Proboscis Monkey Swimming
Proboscis monkeys are regarded as the best swimmers among primates . They have partly webbed hands and feet, which helps them swim and may help them walk better on mud. They have been observed swimming on the surface and underwater and making their across large rivers.
One male proboscis monkeys described in National Geographic crossed a 400-foot-wide river by climbing a 30-meter-high tree and, with a running start, leapt as far as he could, hitting the water with a huge belly flop, and almost knocking himself out in the process. He then swam quickly to the shore. Once a group of proboscis monkeys observed leaping in unison from 15-meter-high trees into the water. The strategy is thought to be a way of staying clear of crocodiles.
Proboscis monkeys don’t have a very good sense of direction. Once a fisherman fished one out of the water that was swimming toward China 500 miles away. They also miss their marks. They are Sometimes end up swimming when they attempt to leap from one tree to another and fall short, into the water.
Proboscis Monkey Behavior
Proboscis monkeys live in groups of 10 to 30 members. They have highly organized social structures. Harem groups, with one male and several females and their offspring, are the basic social units. Males, who are usually kicked out of the group at an early age, form all-male groups that hang out together until they are mature enough to challenge other males and form their own harem groups.
Proboscis monkeys groups generally live in a territory that covers about two square kilometers and stay within 400 meters of a river. They spend most of the day foraging for food. At night they gather in the upper canopy of tree along the edge of rivers to sleep. It is unclear why they sleep near rivers. Sometimes different groups sleep relatively close to one another, an unusual habit among monkeys.
Females generally get along well but they do bicker and squabble over choice sleeping and feeding spots. They often chose the feeding spots and males follow them. Although young proboscis stay pretty close to their mothers, females shar in infant care. Mothers may pass their infants off to one another or older siblings.
Proboscis monkeys are relatively unafraid of humans due their contract with researchers. This is good for tourists who can get close without upsetting them.
Mating Proboscis Monkeys
There seems to be no a single breeding season. Male proboscis monkeys try to scare off rivals with bellowing roars and honks. If that doesn’t work they will jump around aggressively shaking trees and branches. Rarely do they actually fight.
Usually a single young is born after a 166 day gestation period. Young proboscis monkeys have dark hair and a bluish face when they are infants. Families often take turns and help each other take care of their offspring.
Image Sources: Wikimedia Commons
Text Sources: National Geographic, Natural History magazine, Smithsonian magazine, Wikipedia, New York Times, Washington Post, Los Angeles Times, Times of London, The Guardian, Top Secret Animal Attack Files website, The New Yorker, Time, Newsweek, Reuters, AP, AFP, The Economist, BBC, and various books and other publications.
Last updated November 2012