The name ‘orang-utan’ is derived from two separate Malay words: ‘orang’ meaning ‘man’ and ‘utan’ meaning ‘jungle’. They are members of the family Pongidae, large anthropoid apes related to the chimpanzees from the equatorial Africa; gorillas also from equatorial Africa but restricted to the lowlands in the west and the more mountainous regions near Lake Victoria in central Africa. Today, orang-utans are confined to Sumatra and Borneo.
There are two subspecies of orang-utan: the Bornean orang-utan Pongo pygmaeus pygmaeus and the Sumatran orang-utan Pongo pygmaeus abelii. Even an expert may not be able to differentiate between these two subspecies easily but members of the Sumatran subspecies tend to be larger and lighter coloured than those from Borneo.
It is possible that in ancient times, orang-utans were found throughout Southeast Asia. Remains of this creature have been discovered in southern China, Vietnam and Java. It is believed that during the Pleistocene cooling-off period, the orang-utans migrated to Indonesia from Indochina across temporary land bridges. Fossil evidence suggests that the orang-utans that first migrated to Sumatra were about 16 percent larger than the present day form. The extinct variety that once inhabit China are somewhat bigger-possibly as much as 40 percent larger.
Habitat
The orang -utans live in tropical rain forest areas, usually river boundaries or mountain ranges over 6,500 feet. In Malaysia, orang-utans are found in undisturbed and protected forests to the northern and eastern regions of Sabah’s interior. The largest and least disturbed areas that still harbour comparatively large populations of orang-utan in Sabah are the eastern interiors in the Sandakan district, particularly along the Lokan river and the tributaries of the upper Kinabatangan and upper Segama river. Their range also extended southwards across the political boundaries into Kalimantan.
Anatomy
The orang-utans resemble man in many anatomical features even though outwardly they have developed many superficial differences. The long shaggy hairs of orang-utan may grow as long as 18 inches and tends to be longer over the shoulders and arms. The coats comes in shades of orange to blackish brown. This colouration however appears darker with increasing age. Young orang-utans generally have hairs that stick up from the crown of their heads but becomes short and flattened in adults. The face and the abdomen are hairless exposing tough dark brownish skin.
The adult male orang-utan appears formidable and grotesque by human standards. In close up, his face is an extraordinary arrangements of folded skins and protruding bulges of fat. Their massive bulky frame compel them to move only slowly and cautiously through the forest trees. The female orang-utan is much smaller and daintily assembled than her masculine mate. Thus orang-utan are said to exhibit marked sexual dimorphism – the difference in appearance between males and females of the same species – in this case males may grow to double the weight of females.
This slightly exaggerated sexual dimorphism present the males with special mate-winning characteristics when competing among themselves for the females. The males also display threatening gestures in the presence of other males and the effectiveness of these exaggerated and awe-inspiring acts involve visual contacts. The female orang-utans are more likely to yield to the biggest and the fittest-looking males. A dominant male may in fact exercise control over more than one female in his territory. Males are known to fight for the possession of a female at mating time. A peculiar prelude to mating is “singing” by the male which consists of prolonged vibrating burr starting low and increasing in volume to a deep roar before decreasing again and finally ceasing. Pairs may also play prior to mating. They wrestle, slap and mockingly bite each other around the neck and face; all along accompanied by low grunts. Mating takes place in trees and in a hanging position, usually face to face.
Menstruation cycle for a female orang-utan is about 29 days and pregnancy takes roughly eight months. The infant usually weighs between 2 to 3 ½ pounds at birth and will cling to mother’s fur from the start. Normally the baby orang-utan remains under the close protection of its mother until it is weaned at about 4 years of age. During this time it is cared for with a devotion paralleled only by human mothers. She would emit high-pitch screams should the baby try to wonder separately too distant away from her. The male on the other hand plays no part in child-rearing. The mother nurses the baby with her milk for 2 or 3 years and gradually starts feeding its supplementary food in the form of pre-chewed fruits or vegetables. Soon a young orang-utan is able to fend for itself and began associating with others of its own age. The mother now becomes ready to mate again.
The orang-utans, together with the chimpanzees and gorillas, have large and complicated brains, although they are still one-third the size of that of man. They grow very slowly and usually reach maturity at about 10 years or more. Generally they live for more than 30-50 years and infant mortality in the wild is high. Pneumonia, malaria and other infections take a high toll on the lives of orang-utans in their natural surroundings. It has been estimated that of about 5 babies born in the wild, only an average of 3 have a chance of surviving to adulthood and themselves having offsprings.
The arms of an orang-utan are extremely long – the largest and strongest of all apes. When they walk on the ground it is usually in all fours. They are however arboreal too – spending most of their lives in trees. They proceed along the branches of the middle-storey canopy cautiously, silently and horizontally. While moving or at rest in the canopy, they continually manipulates the small branches within their reach searching for food.
A true contortionist of the forest, an orang-utan is capable of clambering, swinging and climbing through vines and branches to reach food in the most seemingly inaccessible places. They are known to consume more than 300 types of forest fruits and an infinite variety of buds, leaves, flowers, barks, even molds and humus.
They have been seen to test for food almost anything within their reach by eating or chewing them. When found palatable, fruits, buds and leaves are stored in the mouth and chewed at intervals. Orang-utans also search for insects and grubs for food. They would use sticks as ‘tools’ to poke, break and get at termites and ants hidden in holes or woods. Honey of wild bees, bird eggs and occasionally soil are also eaten by orang-utan.
Of all the foodstuffs in the forest, the orang-utan seems to have a predilection for the durian fruit. Their protruding lips harbour teeth capable of tearing their way through the prickly covering of the durian to expose the fleshy and succulent contents within. The males usually acquire vast and valuable knowledge as to the whereabouts of such food and the child-preoccupied females rely to a large extent on the male’s guidance from one site to the next.
Ecology space
An orang-utan constructs its nest out of small branches at any place where there is sufficient support, especially in crowns and forks. Broken or bent branches are assembled and laid across each other forming a rough circle of about 2-3 feet in diameter. Nests, found at 10 to 150 feet above ground, are occupied from dusk to dawn.
An orang-utan may sleep in the same nest for several nights if it is situated in an area with plenty of fruiting trees. But as a rule, a new nest is built each night. Additional nest may also be constructed for daytime rest and sleep. Small infants share a nest with their mothers. The youngs start building their own nests at about 2 years old.
In the wild, the orang-utan is predominantly solitary and usually silent. Deep growl may be emitted by older animals in cases of alarm. Upon encounter with an unwelcomed intruder like man, orang-utans are usually very unaggressive, gentle creatures. They have never been observed to kill. Male orang-utans have no natural predators and his dominance in the trees is rivalled only by other males of his kind.
Conservation
The most dangerous enemy of orang-utan is man; who makes inroads into the wild habitats of the orang-utan. Man shoots them for sport or out of ignorance of their peace-loving nature. Now the orang-utan is protected by law in all its habitat areas including Indonesian Borneo, Sumatra, Sabah and Sarawak.
Unfortunately, in some of these areas, enforcement of these laws is far from effective owing to lack of finance, personnels and difficulties of administration. Another significant threat for the continued existence of orang-utan is the increasing pressure of the human population of Sumatra and Borneo. Tropical rainforests are rapidly cleared for agriculture and human settlements as the population of these areas increase. Exploitation of these forests for timber adds new pressures to the preservation of sufficient natural habitat for the orang-utans; putting them in constant jeopardy.
Several large areas have been preserved for these animals to roam under protection in permanent wildlife sanctuaries in Sabah. The Sepilok Orang-utan Rehabilitation Centre near Sandakan and the Danum Valley Field Center near Lahad Datu are two such sanctuaries that have been set aside to ensure orang-utan’s survival into the next century. The primary objective of Sepilok Orang-utan Rehabilitation Centre is to reintroduce orphaned or confiscated orang-utan back to their wild habitat.
Special care which includes nutrition and medical monitoring of these animals are given at the centre. Though allowed to roam freely in the reserves, patient supervisions by trained park rangers are required to revive their instincts of survival in the wild which may have been lost during their period of captivity by man. Releasing them free in the forest also facilitate their social integration with the existing wild population in the reserve. Since its establishment, the Centre has successfully rehabilitate more than 100 orang-utans into the wild.
