Orang-utan

Orang-utan: Pongo pygmaeus

Distribution: restricted to the islands of Borneo and Sumatra.

Habitat: dense tropical rainforest

Description: heavy, rather human-like body. Very long arms, grasping hands and feet. Dark grey skin and reddish hair
           
    

Size: Height: males 1.4 m, females 1.15 m.

Weight: males 90-120 kg, females 40-50 kg.

Life-span: estimated average of 35 years. 50 years or more in captivity.

Food: tropical fruits, leaves, shoots, bark, insects and eggs.

'Orang' and 'utan' are the Malay words meaning 'person' and 'forest'; the orang-utan is literally a 'person of the forest'. Apart from humans, the orang-utan is the only one of the five great apes - the orang-utan, the gorilla, the common chimpanzee, the bonobo (pygmy chimpanzee) and man - to live outside Africa. It is less closely related to humans than the other three great apes, but is still strangely human-looking. The two sub-species living in Borneo and Sumatra differ a little in appearance. Sumatran orang-utans are generally slimmer and lighter-coloured than their Bornean counterparts. The Bornean male has larger cheek pads than the Sumatran, which gives it a more grotesque appearance.


Orang-Utan Habits

Territory: unlike gorillas, common chimpanzees and bonobos, which live in large social groups, orang-utans lead a mainly solitary life. The males constantly move from one area of forest to another. The dominant male ranges over a particular area for several months mating with any receptive females he comes across. When all the females have been mated, he moves on to another area. The adult male advertises his presence to females and other males by making a long, booming call. Adult females spend very little time with other orang-utans, but may occasionally travel together or feed in the same tree - although they don't usually take much notice of each other! Young orang-utans which have left their mother may move around in groups of two or three.

Daily life: the orang-utan is diurnal - that is, active during daylight hours. It lives high above the ground in the forest canopy, moving slowly and carefully through the trees, using all four limbs. The hands and feet are hook-shaped, designed for grasping branches and its powerful arms allow it to swing and climb easily. Because of its tree-top lifestyle, the orang-utan has developed arms longer and stronger than any other ape. Bornean orang-utans may some down to the ground for brief periods each day, but in Sumatra the orang-utans hardly ever venture onto the forest floor, as the Sumatran tiger, a predator, still roams there. When walking on the ground, the feet and hands are clenched and bent inwards.

Fruit makes up half the orang-utan's diet. Orang-utans are very intelligent and seem to be able to memorise the geography of their surroundings and will travel great distances through the forest, managing to arrive in a perticular area just when the trees have ripe fruit. When there is plenty of food in an area, an orang-utan may stay there for as long as the supply lasts, often sharing the area with several other orang-utans; little social interaction goes on and they usually leave singly.

Every night, orang-utans make simple nests to sleep in. They bend branches together to form a platform - it only takes about 5 minutes to build. Sometimes they make a roof over the nest to protect them from the rain. They all sleep lying on their side, cushioning their head on their arms.

Breeding: orang-utans may breed at any time of year as food is plentiful all year round. They do not pair for life and, as mentioned previously, a dominant male usually mates with several females. Gestation lasts for 8.5 months and the baby weighs about 1.5 kg at birth. It is totally dependent on its mother, suckling from her and travelling round by clinging to her body. When a little older, it wanders about on its own, sometimes walking along the branch behind its mother clinging to the hairs on her rump.

The youngster is weaned at around 2-3 years. A youngster may become semi-independent when about three years old but usually continues travelling with its mother until she gives birth again.

Since females do not mate until their last offspring is about six years old, they may only manage to raise two or three babies in a lifetime.

 

Orang-Utans and Man

The orang-utan's distribution has been steadily declining over the years. Its ancestors' remains have been found in 14 million-year-old deposits in Punjab, India. Fossil remains also show that a giant race of orang-utans existed in China 500,000 years ago. They also lived as far south as Java. Today the poulation is restricted to parts of Borneo and the north of Sumatra. In Borneo, its range has come under further threat from the forest fires of last year, which destroyed two million hectares of rainforest, killing many orang-utans, and driving others into the open, forcing them to beg from humans for food.

Another threat to their existence is the trade in baby orang-utans. Many unscrupulous private zoos have in the past paid high prices for baby orang-utans. Today, orphaned orang-utans are sold as pets in Borneo and Sumatra. Baby orang-utans are obtained by shooting their mothers and many babies die before they are sold. A few are lucky to be rescued and taken to special rehabilitation centres to be reared and returned to the forest. The forests to which the orang-utans are returned must be protected to ensure their survival.

These threats have resulted in a huge reduction in the number of orang-utans, particularly since the 1940s, and their slow breeding rate is not sufficient to boost numbers in the wild. As a species they are seriously endangered.

Although breeding them in captivity may be a way to prevent orang-utans from becoming extinct, the only way to ensure their survival in the wild is to protect their forest habitat.

Some of this information was kindly provided by: The Orangutan Foundation, 7 Kent Terrace, London, NW1 4RP.