The slender loris

Jayantha JAYAWARDENE

NIGHT LIFE: The family Lorisidae includes lorises, lemurs, galagos and pottos, and at least 37 species are found in Africa, South of the Sahara, Southern India, Sri Lanka, South-Eastern Asia and the East Indies, except Madagascar.

The Galagos are called bushbabies and pottos are called angwantibos. They are confined to Africa and the lorises to Asia. Lemurs are found only in Madagascar. All these are also known as prosimians.

Slender Lorises are tiny creatures with long slender bodies. Asian lorises and their African cousins, the pottos have either a very short tail or no tail at all. Their heads and eyes are round. The ears are small and almost completely hidden by fur, and the eyes resemble saucers.

The forelimbs and hind limbs of lorises are nearly equal in length. These limbs are pencil thin. Lorises have extremely strong fingers and toes.

This helps them to keep a firm grip on the branches whilst they move about and also stretch for their food. Both the hands and feet are capable of maintaining a powerful grip for astonishingly long periods of time.

Lorises are both arboreal and nocturnal, sleeping by day in hollowed out trees, tree crevices or branches. They generally sleep curled up in a ball, with their heads tucked up under their arms. Those species that sleep in groups curl their bodies one into the next.

When they move, they do so with slow deliberate hand-over-hand movements, moving along as easily under a branch as above. They can move upside down on a branch. If alarmed, they are capable of moving quickly, but they do not jump or leap.

One might take a loris as a rat or a squirrel at a quick glance because of its lithe body and pencil-thin arms. However, closer examination reveals the loris's close-set eyes and the nails on its feet and hands. If possible, a look inside its skull will also reveal a large brain.

Lorises have an unusual formation of their lower incisor teeth and the canine teeth forming a comb like structure. This is known as the tooth comb. It is used to catch its food and also to groom its fur. Grooming is to keep, like most primate species, the fur and skin free of insects and parasites.

The odd appearance of the loris has led to its name. The Dutch thought the diamond patches around its eyes gave it the appearance of a "lori" or a clown.

The awkward and sometimes alien appearance of its young ones has led to the Sinhalese proverb "unahapuluwge daruwa oota menikak lu." Though this phrase, "the young loris is a gem to its mother", it is based on the idea that only a loris baby's own mother could love such a bizarre-looking creature.

In Tamil, it is known as Thevangu, a phrase often ascribed to people who are too thin. In Sinhala the Grey Slender Loris is known as Alu Unahapuluwa and the Red Slender Loris as the Rathu Unahapuluwa. The greatest misconception about the loris was given by the British, who dubbed it as the Ceylon sloth.

Despite its unique physical appearance, it is closely related to humans. Its geographic distribution is relatively small and lorises had never been studied in the wild in Sri Lanka in great detail until Anna Nekaris did.

This is probably due to the fact that lorises are small bodied, only come out at night, and move in silence, making them difficult to detect, if one is not specifically looking for them. Finding them, even after looking for them carefully, is difficult. Sometimes the whistling sound they make gives them away.

In Sri Lanka there are two species of loris, the Red Slender Loris (Loris tardigradus) and the Grey Slender Loris (Loris lydekkererianus).

The red slender loris is restricted to Sri Lanka's wet zone, where pathways have been created by a collection of intertwined branches from a number of adjoining trees. These branches, vines and lianas make it easy for the loris to move about.

In addition to providing greater opportunities for the loris to acrobatically negotiate this complex arboreal network, this moist habitat offers a greater variety of food options to red slender lorises. These feeding opportunities are not so readily available to the lorises living in drier areas.

Four subspecies of the loris are found on the island. They are the wet zone subspecies (Loris tardigradus tardigradus), the dry zone subspecies the Northern Ceylon Grey Slender Loris (Loris lydekkererianus nordicus), found in lowland dry zone of north and east including Jaffna, and the highland subspecies.

The Highland Ceylon Slender Loris (Loris lydekkererianus grandis) is found in the central province at an altitude of 900 meters.

The Montane subspecies, the Horton Plains Slender Loris (Loris tardigradus nycticeboides), is known only from the type locality and is restricted to mountain rain forests and mist forests at an altitude more than 1500 meters.

The first three species are endangered and the fourth, the Horton Plains species, is critically endangered.

The Horton plains slender loris is in the IUCN red data list of 2003 .It is very rare and known from two animals found in 1937 by Mr. A C Tutein Nolthenius on the Horton Plains. Tutein Nolthenius was a tea planter on an estate close to the Horton Plains.

These animals and their two off springs died in captivity. Since then, there was only one unconfirmed report till it was rediscovered by Anna Nekaris, who managed to see one and eyeshine another probably belonging to this species.

Eyeshine is when an animal's eyes glow in the light of a torch flashed at it in the dark. This subspecies has now been considered for inclusion in the list of 25 most endangered primates.

Anna Nekaris has suggested that the slow-climbing adaptations that distinguish lorises from the closely-related bushbabies may have emerged as a response to a low-quality diet.

Unlike the bushbabies, which mainly consume high-energy arthropods and fruits, lorises tend to specialize on insects and leaves that are either of low quality or toxic.

During a survey carried out in 2001 by Anna Nekaris and myself, it was found that nearly all of the areas within an hour's drive from Colombo, both up and down the wet western coast, in areas such as Kesbewa, Matugama and Bandaragama, lorises have been found prior to 1933.

Consequently, such areas were deforested and the remaining populations of these sub species are clinging on to small isolated patches of forest.

The earlier conception was that lorises were primitive, slow and solitary. However, recent research has shown that this is not so. The loris is a very difficult species to research in the wild.

It is nocturnal. It lives in the foliage and freezes as soon as it senses danger. Now much more is known about the geographic distribution, abundance and behaviour of this tiny primate.

Lorises are the most faunivorous of primates. They specialize in consuming small insects etc. They are not affected by the toxicity of some of their prey like ants and darkling beetles. They generally eat the head of the prey first.

However, one loris that I had in captivity, when I was in the Mahaweli project, ate a scorpion (Gonussa) that had crept into its cage, died in a day. They do not seem to eat any leaves, flowers or fruits. Lizards and Geckos are consumed with obvious relish.

Those insects which emit irritant sprays are removed individually from the colony, taken several meters away, and consumed. While the loris closes its eyes tightly, and shakes its head, all combined to produce what can be aptly be a face depicting disgust.

In our study we found that although the gum, on the bark of trees, comprised a portion of the diet of the dry zone Grey Loris, it was not seen to be consumed by other sub species. The consumption of plant material was minimal to nonexistent.

However, vertebrates, particularly geckos and lizards, were consumed by all subspecies but comprised a large portion of the diet of the wet zone Red Loris.

Lorises cannot jump like monkeys do. They move from branch to branch by stretching across. Since lorises cannot move about fast in the trees of their habitat, they stay quite still without moving and camouflage themselves to escape from predators.

Some facts about the loris, a native of southern India and Sri Lanka, have been known for some time, but despite being the subject of numerous, now-obscure, nineteenth-century reports, this small, nocturnal, gremlin-like primate went unexamined for a long period by primatologists.

It is only in recent decades that systematic studies on the prosimians, a suborder of primates, have begun. The earliest of these modern investigations, emphasized the various physical and social similarities of these species, to reconstruct their behaviour for the first time.

The first systematic study of the slender loris in Sri Lanka was done in 1970 in Polonnaruwa and Udawattekele, by Peter and Hladik.

These French naturalists were among the pioneers of nocturnal primate research, and over a short time span, they accumulated a remarkable amount of factual information regarding the natural history of the slender loris. Key among these observations was that the loris is almost primarily insectivorous, rather than relying on fruits or leaves.

A long-term study has shown that lorises were among the most carnivorous of primates, with their diet consisting 96% of animal materials.

In fact, their preferred food items were ants, which they devoured with much relish. The physiological adaptations required to consume large numbers of ants are found only in a few groups of mammals.

However, they are found among some members of the order Edentate (which comprises of anteaters, sloths and pangolins), which consume both toxic ants and tannin-filled mature leaves.

The 'slower' movement of lorises is probably a physiological adaptation, necessary to digest the toxins found in their preferred food items.

However, it is important to note that lorises do not always move slowly. Their movements may seem so due to their mode of progression, which is a hand over hand stretching, spiraling and twisting, as opposed to active leaping by other primates.

Research on the Sri Lankan lorises revealed an even more interesting aspect of their movements. Slender lorises in India were never observed to run.

Running involves active lateral movement of two limbs, with two other limbs in contact with a substrate; this had never been seen among Indian lorises. Rather, the 'cautious' loris typically maintains a grip on a tree branch with at least three of its spindly limbs.

However, lorises at Giritale and Polonnaruwa were observed to run in the manner described above, and even to catapult themselves between gaps in the canopy in a manner resembling leaping. These types of movement sequences were observed at night, and were by no means one-off experiences.

Even more surprising was that the wet zone species, an animal nearly one-third the body size of its northern counterpart, engaged in this behavior frequently, covering 20-30 m in the matter of minutes rather than over the course of an entire night.

Sri Lanka already has been declared a conservation biodiversity hotspot by the IUCN. The realization that the genus Loris really is comprised of several species has increased this biodiversity. Further evidence that the slender loris is indeed more than one species also has been found in the way they communicate with one another.

It has already been stated that the Sri Lankan lorises look quite different from one another superficially; however, they may not appear so different from one another as a lion does from a tiger.

This is because the nocturnal world of the loris is an olfactory (smell) and auditory (sound) one rather than a visual one.

Animals recognize one another less by the way they look than by the way they smell and sound.

The slender loris has a repertoire of about 16 calls, the loudest of which is a thin shrill cry or whistle. This call has given the loris the nickname of forest baby, and in other parts of Sri Lanka, the reputation of a forest witch. These different whistling sounds are being analysed by researchers now.

One aspect these two species of lorises shared in common with each other, and with the monkeys to whom they are so closely related, was a propensity to be social. Many naturalists often report seeing a loris alone or in pairs.

However, in the excitement of sighting a loris, he or she may have missed the other four or five loris in the trees close by. If the torch were flashed the other lorises too would have been seen clearly. Both males and females care for the young, a trait rarely seen even among monkeys, and animals sleep in groups of up to six or seven.

In fact, at Polonnaruwa, nine and possibly eleven animals were seen together in one tree. These animals played, foraged and groomed one another for nearly two hours.

Why has the loris been so misunderstood? The number one reason is, of course, its nocturnal habits, which limit observation of this animal. Few people have the patience to follow the loris through its 12-hour nocturnal cycle of activities.

When a loris does not want to be seen by you, all it needs to do is close its eyes, concealing the shining reflective layer that allows naturalists to locate these creatures from a distance of up to 100 m.

Furthermore, the eyes of the loris are designed to absorb vast amounts of light in its dimly lit world. Nothing can be more disturbing than to barrage these creatures with a glaring white beam of a torch.

If there is a desire to observe these animals, this problem is quickly remedied by covering the torch with a layer of red glass paper. The color then produced by the beam is at the fringe of the animal's visual range, allowing it to continue on its nightly path without disturbance.

Despite their ability to go undetected, lorises still face many dangers in Sri Lanka and have been declared endangered by the IUCN. They are often killed while crossing power lines, or struck by vehicles while crossing the road.

Less frequently, they are kept as pets, or killed for their eyes, which are deemed to have medicinal value. Actually they do not make great pets since they are nocturnal. They spend the day curled up in a corner of their cage and are active only by night. Only with more awareness of these animals can their plight really be addressed and remedied.

From interviews carried out amongst the villagers living close to loris habitats, we found that most of them had a negative attitude towards lorises. This was due to the lack of personal knowledge of the animal, which they rarely see.

These interviews showed that local opinion of the loris was based on hearsay and traditional folklore both of which are generally negative. Actual knowledge of their biology and ecology is lacking amongst the villagers. They will kill a loris purely because they think it evil.

In earlier times, villagers used to hang lorises, upside down, over a low fire so that the smoke would make the its eyes tear. These tears were collected and used for medicinal purposes. I believe that this practice has now been done away with.

This is not done just to see the its large eyes burst as some believe. I do not think the eyes burst at all but the loris used to die eventually.

Anna Nekaris has helped me with facts that she gleaned during her study here.

romalijj@eureka.lk