ORANGUTAN FACT SHEET

The orangutan is Asia's great red ape, and is an endangered species. In the wild, it can only be found on the islands of Northern Sumatra and Borneo, in lowland tropical rainforest areas with complex canopy structures. There are two subspecies of orangutan, the Bornean (Pongo pygmaeus pygmaeus) and Sumatran (P.p. abelii), which are slightly different from one another. The Bornean subspecies is usually darker and the cheek pads are larger than the Sumatran subspecies.

The word orangutan is Malay meaning "Man of the Woods"; appropriate, as it is the only truly arboreal (tree dwelling) ape. Its very long arms and hook-shaped hands and feet are adaptations to its arboreal lifestyle. Nests are built in forest canopies at night, for sleeping, made from interwoven branches and leaves. Adult males grow to about five feet and weigh an average of 120kg, while adult females only grow to about four feet and weigh 45kg.

The bulk of an orangutan's diet is fruit, but they also eat bark, leaves, shoots, buds and stems. They have also been known to eat insects such as termites, mineral rich soil, honey and even to steal eggs from nests in the trees.

Orangutans are not sociable like their relatives, the chimpanzee and gorilla. The males wander alone and females are accompanied by their infants or sometimes an older juvenile. This is largely because favoured fruits are usually widely dispersed and can't support large groups. Orangutans, however, are sociable during the high fruiting seasons in the rain forests and thus their movements are very dependant on the presence of ripe fruit. A distinct pecking order exists in times of high fruit production, both in males and females. There may be a high degree of territorial overlap and as many as six males may range independently over a given area at the same time.

Adult males have cheek flanges which enlarge their face during aggressive displays with other males. These encounters are used to establish male hierarchies and if contact is made, can sometimes be deadly. But this occurs infrequently, and orangutans prefer to avoid confrontation, and call to advertise their presence. Only the male vocalises using his throat pouch which inflates during calling. This adds resonance to the territorial 'long call', which is a series of loud roars which rises to a crescendo before dying back to low groans, and is usually accompanied by branch-breaking. The exact reason for this call is unknown, but it is thought that it serves the function of attracting receptive females as well as letting other males know of each other's whereabouts. Adult males reach sexual maturity between 8 and 15 years and will develop cheekpads and throat pouch as late as 20 years.

A female reaches sexual maturity at 9 to 12 years old, and can be expected to give birth to three to four offspring in her lifetime (once every eight years on average). Each pregnancy lasts 260-270 days, and a mother rears her infant on her own. Very rarely are twins born. The infant is not fully weaned until it is three years old, and will remain with its mother until she gives birth to another. This means that mother and young may stay together for up to 6 years. Young orangutan are more sociable than adults and often gather together to play. Although a sexually mature male may roam to find receptive females, orangutans usually only travel a few hundred metres through the trees each day. Orangutans can be expected to live between 35 to 50 years in the wild.

Threats to Orangutans

• Ten thousand years ago, orangutans ranged as far as north China and far south into the Indonesian island of Java. Best known estimates today suggest that only about 22,000 and 5,000 remain on Borneo and Sumatran islands respectively. It is estimated that in the last 10 years the orangutan population has halved.
• The greatest threat to the orangutan population is the destruction of its lowland rainforest habitat for conversion to plantations and agriculture, and logging for timber. Fire and logging leaves isolated patches of forest which prevents interbreeding between populations. Rainforest clearing exposes the orangutans to hunting for meat and enables the kidnapping of juveniles.
• As infants are dependent on their mothers for about seven to eight years old, the mother is often clubbed or shot to death to capture the infants. The largest market for kidnapped orangutans is private pet owners. Trade to zoos, laboratories and the entertainment business, however, also play a part.
  

• A new Orangutan project is under consideration.  Please stop back for more details.