Nature Trial

Two monkeys endemic to Lanka

This little island home of ours is rich in fauna and flora, some of which are endemic to our country, protecting them is our duty.

However, daily we hear or see reports of how our valuable forest cover and endemic plants and animals are being destroyed; sometimes people from other countries try to smuggle certain animals and plants endemic to our land out of the country.

There are many animals and plants endemic to Sri Lanka, so today we decided to introduce you to two monkeys endemic to our country, since we have been enlightening you about primates through Nature Trail, over the past few weeks.

The two monkeys we feature are the Purple faced leaf monkey and the Toque monkey. However, these two are not the only primates found in our land. There are two others - the Grey monkey also called the Gray langur, and Slender Loris, which we'll write about on a later date.

Purple faced leaf monkey (Thrachypithecus vetulus)

This Old World Monkey species is endemic to Sri Lanka and was once common even in the suburbs of Colombo (west zone villages), but today it is listed as endangered. It has been listed as a threatened species in the IUCN Red List. It is the largest primate in our country.

Due to urbanisation and also as a result of being hunted for food and skin to make drums, the monkey's existence is at high risk in the wild.

The purple faced leaf monkey is popularly known as the hali wandura or kalu vandura' (Black monkey) in Sinhala and is found high up in the canopy of the Sinharaja Forest, Kitulgala, and the mountains of Horton Plains National Park.

Four distinct subspecies have been identified. They are the southern lowland wetzone purple faced leaf monkey (ventulus ventulus), the northern lowland wetzone purple faced leaf monkey (ventulus nestor), dry zone purple faced leaf monkey (Ventulus philbricki) and the Montane Purple faced leaf monkey or bear monkey (Ventulus monticola).

This long tailed diurnal (daytime) and arboreal (related to trees) monkey is brownish black in colour overall, with a darker face. Whiskers range from white to pale brown and are directed backwards.

The head and body length is around 44.7 to 67.3 cm while the length of the tail ranges from 58.9-85.1 cm. Average body mass for an adult male is around 8.5 kg. A female weighs about 7.8 kg. The pelage (coat) colour of the newborns are pale grey with a brownish tinge on the chest, legs and arms.

Crown is also pale grey with a brown tinge. The naked or hairless parts of a newborn's body are pink in colour. Two distinct features leaf monkeys have are sacculated stomachs (like in some ruminants) to assist in the breakdown of cellulose and enlarged salivary glands. This type of monkey also has a relatively short thumb.

Even though it is considered to be a folivorous (leaf eating) monkey it consumes fruits, flowers and seeds. However, it prefers to eat immature leaves more than mature ones because tender leaves are high in protein and law in lignin (organic substance which forms characteristic part of all woody fibres).

The monkey is rather selective in diet and the leaves it eats come from 12 species of trees. It likes to eat only fibrous fruits. Generally it increases the consumption of fruits during May and June because fruits are available in plenty. Now, how do you think the monkey obtains its daily requirement of water? By licking rainwater off leaves and branches and drinking water collected in tree cavities.

During the dry season, July to September, it eats more flowers. From December to January, leaves are an important part of the diet.

The purple faced leaf monkey, like all monkeys is a social animal and lives in a troop which could number between 3 and 16 individuals. However, it has a unimale social structure with one male to about seven females. Some groups may have two adult males. All male groups also exist with about 2-14 individuals.

Even though these monkeys are territorial, the home ranges of all male groups may overlap the home ranges of unimale groups. However, the home ranges of unimale groups will never overlap.

The territorial calls of these monkeys echo through their forest habitats. This territorial call known as the great call is emitted spontaneously by the adult male of the group at the sighting of an intruder or as a response to a loud noise.

The full, deep throated call made by the adult male in the early hours of the morning is known as the 'hooh call. The shrill sqeak is made by curious individuals while the infants in distress would make a high-pitched whine. In addition to vocal communication, the monkeys resort to ol factory, visual and tactile communication.

These monkeys are good at leaping and in fact, it has been observed that they could drop 50 or more feet down from the tree canopy when making the "great call" sequence. They generally move quadrupedally (on all four limbs) when travelling about and are said to be twice as fast as toque monkeys.

The female gives birth to a single offspring. By 12-16 weeks, the coat resembles that of the adults, but it gets the complete colouration and appearance only by about 28 weeks. By 12-20 months, it eats solid food, is independent of mum and also engages in social play.

When the offspring reaches 28 weeks it's fully independent and weaned off mother's milk. Male monkeys tend to ignore infants.

If you happen to make a trip to the famous Sinharaja forest or any of the areas this monkey inhabits, see if you could spot this monkey and observe its behaviour.

Endemic monkeys Fact file

* The four subspecies of purple faced leaf monkeys are: Ventulus ventulus whose overall colouration is grey-black with light tipped hairs. The head and cheek whiskers are brown or grey-white. Tails are light brown with long creamy tips. (Found mostly south of the Kalu Ganga area)

Ventulus nestor - These monkeys are more grey-brown than above subspecies. The rump patch is silvery grey and forearms and shanks are almost black. But the crown and nape are pale brown and the tail is slightly tufted at the - tip. (North of the Kalu Ganga)

Ventulus philbricki - resembles the above subspecies very much, but these particular species have a less conspicuous rump. The lower parts of the limbs are black, the tail is pale; tawny to white and not tufted (found mostly in the north and east of the country in the dry zone.)

* Ventulus monticola has a very thick, brown coat. Cheek whiskers are long and white hiding the ears. The tail is comparatively short. (The monkey is found in mountains in attitudes ranging from 1,200 to 2,000 mts.)

* Two types of monkeys from the family Cercopithedidae are found in Sri Lanka - macaques and langurs. There is only one macaque, the toque monkey which has 3 subspecies. Purple faced leaf monkey and the grey langur both belong to the other category (langurs).

* There are about 234 different primate species in the world and around 90 per cent of them are found in the tropics. Our country has four.

* Langurs are believed to be the reincarnation of the Hindu monkey God Hanuman. The grey or Hanuman langur, as it is also called, is found in India too.

* Toque monkeys of the hill zone have longer hair and is stockier than the other two subspecies.

* Macaques have no hair nor whiskers on the faces like the languars.

Toque monkey (Macaca sinica)

This Old World monkey is the only macaque monkey in Sri Lanka and is endemic to our country. In Sinhala it is known as the rilawa, and in Tamil as korangu. It is a common sight especially in the Cultural Triangle.

As a result, it has earned the nickname 'the temple monkey'. However its original name toque is as a result of the distinctive, circular shaped tuft of hair on its head which resembles a toque, a type of beret(round,close fitting hat) worn in mediaeval Europe.

Three subspecies have developed and they are grouped as the wet zone, hill zone and the dry zone monkeys.

Due to the reddish brown colour of its coat, it is also known as the red monkey. It was classified as vulnerable in the IUCN Red List in 2000. But its present status may not be so.

This monkey is a compact, short tailed animal weighing about 8.4 kg, with a head to body length of 35-55 cm and a tail of about 40-60 cm. Females are smaller than males. While the females stop growing by the age of 5, the males continue to grow until they are 7 years old. Their faces are flesh coloured.

They live in troops and prefer to haunt lowland and semi-deciduous forests near permanent water bodies. They have multi-male and multi-female troops with 2-3 females per male.

Their social system is complex with a clearly male dominated hierarchy. The male demonstrates its power by snarling, shaking branches and walking with its tail and head held up. The troops which are rather large are made up of family groups and each family group is led by the oldest female.

Such family groups consist of all related females such as daughters, sisters, aunts and granddaughters. Most males leave family groups after adolescence (when they are between 4-6 years).

Most often the adult males live in the peripheries (the outer edge) of other troops' home ranges until they are strong enough to challenge and take over the troop from the leader. Each troop has its own home range, the size of which depends on the size of the troop.

The leaders of the troops generally have a good knowledge as to when and where food resources and also water is available during the dry season. This information is passed down from generation to generation with the new experiences the troops gather added to the available info.

Young monkeys are taught by mum and others in the troop. The toque monkeys have cheek pouches. When food resources are limited or when they want to steal food, these pouches come in handy to store as much food as they want.

As toque monkeys are not a rare sight, you may be able to see how one side of their faces are bulging at times due to the excess food they've stuffed into their cheek pouches.

Now what is the food they eat? As these monkeys are not selective about their food like the purple faced leaf monkeys, they have a variety of foods to select from. Apart from the usual tender leaves, seeds, fruits and flowers they have in the menu card, they also consume some domestic foods such as rice, bread and vegetables.

They seem to like eating lotus seeds because they have been observed wading in the water to eat them. They also eat animal matter made up of small vertebrates, reptiles and birds.

These monkeys too are diurnal and spend most of their time on the ground or on trees.

The offspring born after a gestation period of 165 days weigh about 400 g at birth. The young are very playful and anything they can lay their hands on such as sticks, stones, the adults and their tails especially become 'toys' to them. They can be cute and fascinating as kittens.