LANGURS AND LEAF MONKEYS - Part 2

Jayantha JAYAWARDENE

LANGURS: The Sri Lankan Grey Langur (Semnopithecus Priam) is called Hali Wandura in Sinhala and Kornagu in Tamil. Langurs are found in most parts of the dry zone but are not seen in the wet zone or the hill country. Its southern most point on the west coast is north of Puttalam.

It is seen mostly in wooded areas but less frequently in rural and urban areas. Langurs are found in the Indian sub continent too.

In India, these monkeys are also called Hanuman Langurs, after the monkey god Hanuman in the Ramayana. It was also called the Entellus monkey.

The Grey Langur is light greyish in colour, which moves towards a brown colour. The colour variations are seen amongst the different troops but rarely within the troop.

The langur has a black face with prominent whiskers. It has a crest of upstanding hair on the top of its head. It has long and lanky limbs and a long and slender tail. The males have well developed canines, and are larger than the females.

Langurs feed on leaves, buds, shoots, fruits, flowers, and some types of grain. The leaves are preferred when they are tender. Flowers and fruits are seasonal and so their diet varies during the year. They also raid village gardens for fruit if their habitat is close to a village.

In the dry season, when the tanks (reservoirs) dry up, langurs dig up the yams of the lotus (Nelumbium nelumbo) that grows on the tank bed and eat the seed. However, I have not seen them dive into the water to collect lotus seeds as the macaques do.

Monkeys are the favourite food of the leopard. Crocodiles also eat monkeys when they get the opportunity. These monkeys always come to the edge of a tank, stream, water hole or puddle to drink.

But when approaching larger water bodies in the jungle, they come stealthily because there may be a leopard lying in wait in the shadows or a crocodile at the waters edge.

Grey Langurs move about in troops. A troop consists of both males and females of all ages ranging from old feeble members to babies.

Usually, a dominant male leads a typical troop consisting 12 to 25 monkeys. This male is challenged regularly for the leadership. A fight ensues and the victor, if it is the incumbent male, remains or if it is the challenger, takes over. When a new male takes over the troop, it kills all the young. This is for two reasons.

First, it prevents any males growing up and challenging for the leadership. Next, without babies the females are able to allow the male to mate at anytime.

Generally, one baby is born at a time but on rare occasions twins have been seen. The gestation period is about six months. When the female is in eostrus or ready to mate, it is the female that approaches the male and entices him to mate. There may be several matings a day.

The baby clings on to the mother and suckles regularly. The baby is carried by the mother for four to five months. However, when it is weaned, it strikes out on its own.

Large troops of these monkeys are seen in Kataragama. They beg and steal food from the devotees who come there. They also hang around due to the availability of fruits and flowers disposed from the shrines.

These monkeys have adapted themselves well to humans. They are not frightened of humans from who they get little trouble. However, they are wary of humans and are always on the look out for a negative reaction from them.

They are arboreal and terrestrial moving freely on the ground as amongst the trees. They lope or walk on the ground with their long tails held in the shape of an S. They are diurnal and not active at night.

They love to sit on rocks when on the ground or amongst the ruins in Anuradhapura and Polonnaruwa.

The troops have their home range and rarely move out of this area. They are inquisitive and will investigate anything new they find like the mirror of a vehicle. They also like to sit on a roof of a building.

Emmerson Tennent, in his book, says, "A flock of them will take possession of a palmyrah Palm and so effectively can they crouch and conceal themselves among the leaves that, on the slightest alarm, the whole party becomes invisible in an instant.

The presence of a dog, however, excites such an irrepressible curiosity that, in order to watch his movements, they never fail to betray themselves."

Last week, I wrote how curious the macaques' are, and how they get into trouble with a leopard. The same happens to the langurs as well. When the monkeys are feeding, they keep a monkey on guard perched on the top of a tree, always on the look out for a leopard.

On seeing the leopard approaching, it alerts the rest of the troop which sets up a cacophony from the safety of the tree tops. The python (Python molurus) also predates on the monkeys when it gets a chance.

Grooming each other and themselves is an activity that they indulge in regularly. As a result most monkeys of all three species are relatively free of parasites. Parasites are those that feed on the blood of the host monkey. Lice and jungle ticks are the parasites that are likely to get onto monkeys.

The Leaf Monkeys

The Purple-faced Leaf Monkey (Trachypithecus vetulus) is called Kalu Wandura in Sinhala and Korangu in Tamil. This species is endemic to Sri Lanka. The Purple faced Leaf Monkey is divided into four distinct sub species.

Leaf Monkeys are found in monsoon scrub, mature secondary, semi-deciduous, and undisturbed cloud forests. They generally like well-wooded areas but are also seen infrequently in urban areas. Each of the four sub species of the Leaf Monkey occupies distinct forest areas.

Leaf Monkeys, like the Gray langur, have long-tails. They have a dark face mask with a paler lower face. The loud barking call, particularly of the highland species, can be mistaken for the roar of a predator such as a leopard. They are mainly arboreal but descend to the ground rarely.

However, I have not seen the Bear Monkey (Trachypithecus vetulus monticola) on the ground. In any case, even if they do descend to the ground, they would be difficult to be seen due to the thick undergrowth in their habitat.

This species has a stocky or heavy body. The hair on top of its head, unlike the Grey Langur, is directed back wards and does not show as a crest. However the hair on the head is semi erect. The fur on the body is of dark colour.

Several detailed studies that have been carried out in the past on this species by a number of researchers have revealed much on their behaviour and family structure.

The Purple-faced Monkey is mainly a leaf eater, but it will also consume fruit, flowers, and seeds. It prefers immature leaves to the more mature ones because they are high in protein.

C. M. Hladik says that most of the food eaten by this species come from twelve tree species: Kolon (Adina cordifolia), Kon (Schleichera oleosa), Weera (Drypetes sepiaria), Ruk Anguna (Alangium salvifolium), Neralu (Elaeodendron glaucum), Bora Damuna (Grewia polygama), Madung (Syzygium cumini), Goda Kirilla (Holoptelea integrifolia), Mangosteen (Garcinia spicata), Kirikon (Walsura piscidia), Bo, Nuga (Ficus spp), and Kaha penela (Sapindus trifoliatus).

Kolon accounted for 40% of the diet at Polonnaruwa, with the leaves, flowers and fruits,. Kon and Weera together accounted for 30% of the diet.

The subspecies Trachypithecus vetulus monticola was found to have a diet consisting mainly of young leaves, mature leaves, flowers and fruits. Hladik has also found that the fruits the purple-faced langur preferred to eat tended to be fibrous and desiccated, whereas the Gray Langur preferred to eat fruits that were mature and fleshy.

The diet strategy of the purple-faced langur minimizes the expenditure of energy while sacrificing for a relatively low nutritional gain by being less mobile than the Grey Langur. This species does not move about as much as the Grey Langur.

Many of the flowers and fruits are seasonal. Therefore, they have a large variety to choose from. These are also seen to eat insects but this is not a regular part of their diet. Like the tame macaques these monkeys also eat a variety of domestic food like rice, bread, vegetables etc.

This species has been observed to consume earth from termite mounds. Water is obtained by licking rainwater off leaves, branches and drinking water collected in tree cavities.

Predators of the purple-faced langur include humans and leopards (Panthera pardus).

The purple-faced langur has a single male social system, with a male having up to seven females in the harem. The basic group includes the resident adult male, one to seven adult females, and a number of sub-adults, juveniles and infants.

Some groups may have two adult males. All-male groups exist, having numbers from 2 to 14 and having their own territories.

All-male groups will also split-up during the day, only to regroup at the sleeping site at night. The size of a troop ranges from 5 to 20 individuals. This species is arboreal and active during the day. However, it will move on the ground when there is a lack of trees, but their stay on ground is brief.

The leaf monkey is a territorial species and the resident male will defend its territory aggressively against groups of the same species. Takeovers of the harem group by males from all-male groups have occurred.

Harem group males will spend part the day in watching out for intruders to the home range, sitting in vantage points, such as the crown of a tall tree.

Harem males will also attack other males and whole groups by chasing and even attacking individuals. Sometimes the intruder is killed in such attacks. The most common form of attack is two males grappling each other and falling to the ground.

Hladik says that adult females will also join in on territorial defense with a reduced version of the territorial display. Because of this territorial aggression, lone females have a difficult time trying joining a harem.

Females will approach the harem male slowly, then turn away not staring at the male and always keeping the back to the male. This mimics sexual behaviour and may reduce the aggression of the male and allow the female to join the harem.

Females may also join a harem when there is a takeover of the harem by another male; the female would be no less foreign than the harem females.

Infanticide occurs when a new male takes over the leadership of the troop. Often, the infants are killed by the male and to a lesser extent by the mothers. The new male also kills off the young so that he will be able to mate without hindrance.

According to Hladik, there are several types of calls emitted by leaf monkeys. The dominant male of the harem emits a territorial call in response to the sighting of an intruder and a similar call after the eviction of intruders. This call is emitted spontaneously or as a response to loud noises.

During this behaviour the performer will run vigorously, bounding through the trees and make exaggerated dropping leaps. The full, deep, throaty call given by adult males in the early morning is called the hooh call.

A shrill squeak is emitted by individuals when they are curious. Twitters are birdlike in nature and are emitted when an individual is expressing pleasure or excitement. The high-pitched call emitted by the infant when distressed is called the infant whine.

The Purple-faced Monkey gives birth to a single offspring. In Polonnaruwa, the mating season may be from October to January, which coincides with the beginning of the peak period of rainfall, food abundance, and declining temperatures. A birth between May and August also may exist in Polonnaruwa.

In the Horton Plains, a distinct birth peak has not been established. In the Horton Plains a birth peak may not be found because of high availability of food and rainfall throughout the year. The gestation period ranges from 6 to 7 months.

In Polonnaruwa, Rudran found that adult females will initiate sexual behaviour first by head-shaking, then presenting to the adult male. Head-shaking is where the female shakes her head back and forth before she presents to the male.

In 12-16 weeks the infant resembles the adult pelage coloration and the infants become more independent of the mother. They also begin to engage in social play. Social play in the purple-faced langur includes: chasing, light wrestling, and swinging from branches. Infants begin social play from 4 to 5 months of age.

At this age the infant also begins to eat solid food. When they are about six months the young are reliant solely on solid food and move about on their own.

However, if there is a situation of danger, the mother will take away the baby to safety. Males tend to ignore infants even when they get into physical contact with them.

The Montane or Highland Purple-faced Leaf Monkey (Trachypithecus vetulus monticola) is also called the Bear Monkey, and bigger than the other species with more fur on the body. This sub-species has very thick, brown pelage.

The cheek whiskers are long and white, hiding the ears. They have short tails. This sub-species is found in the mountains at altitudes from 1,200 to 2,000 meters. They are seen regularly in the Horton Plains National Park and the Hakgala Gardens and Hakgala Nature Reserve.

The Western Purple-faced Leaf Monkey (Trachypithecus vetulus nestor) is lighter and more gray-brown than Trachypithecus vetulus vetulus. The rump patch is silvery gray. The forearms and shanks are nearly black in colour.

The crown and nape are pale brown and the tail is slightly tufted at the tip. This subspecies is found from the north of the Kalu Ganga as far north as the rainforests.

The Northern Purple-faced Leaf Monkey (Trachypithecus vetulus philbricki) is like Trachypithecus vetulus nestor except that it has a less conspicuous rump patch. The lower parts of the limbs are black and the tip of the tail is pale, tawny to white, and not tufted.

This subspecies is found in north and east Sri Lanka in dry zone, up to 1,500 meters in East Matale and Madukelle Hills.

The Southern Purple-faced Leaf Monkey (Trachypithecus vetulus vetulus) is called Alu Wandura in Sinhala and Mundi or Korangu in Tamil.

The overall coloration of this subspecies is gray-black with light-tipped hairs. The lumbar region, haunches, and the distal part of the tail are light brown with long creamy tips.

The head and cheek whiskers are brown or gray-brown.

The range of this subspecies is the low country wet zone in the area bordered by the Kalu Ganga, the area south of Kalutara going south to the Tangalle area. On the other side, its range goes to Rakwana hills and almost upto the Peak Wilderness.

It is comparatively shy, but known to raid village gardens. It very rarely approaches houses. Leaf monkeys are eaten in some parts of the country. The flesh is known to be tasty having a leafy flavour.

Prof. Colin Groves has helped to identify these sub species.

Pictures: www.zero3images.com

romalijj@eureka.lk