Created | Updated Oct 12, 2015
Orangutans, Pongo pygmaeus, are anthropoid apes, native to the forests of Borneo and Sumatra in South East Asia. The word orangutan means 'man of the forest' in Malay. The orangutan population is nearing extinction because of man's intrusion on its habitats, and currently they are on the Malaysian Government's endangered species list. The Orangutan Foundation International serves to support the conservation and understanding of the orangutan and its habitat. The foundation also cares for individuals who are released into the wild.
Biruté Galdikas is the Dian Fossey, or the Jane Goodall, of the orangutan world. She established the Orangutan Foundation International and has learned more about orangutans than anyone, being driven by her desire to understand why the orangutan evolution took a different path to our own.
The adult male orangutan is usually between 1 and 1.4m tall (3'2" - 4'7"ft) and weighs around 90kg (198lb). The adult female only reaches a height of between 0.8 - 1.1m (2'7" - 3'7") and a weight of about 50kg (110lb) - orangutans are around two-thirds the size of a gorilla. They tend to live for around 30-45 years in the wild.
Orangutans are covered in a long, reddish-brown hair, which grows thickly on the arms and the thighs. The arm-span of an orangutan can be up to 2.3m (7'7") in the largest males, but they have short legs and a relatively square body. The hands and feet of orangutans are similar to our own hands, with four long digits and an opposable thumb or big toe. They are able to use these hands and feet to grab objects. The head of the orangutan is large, with a prominent mouth area. Adult males have cheek flaps made of subcutaneous fatty tissue, as well as an air sac that forms a bag-like swelling which hangs from its throat. This can inflate, producing the long call, a groan that can be heard from up to 1km away. This is how orangutans communicate between each other, including informing other males of territory boundaries and calling to females.
Almost exclusively arboreal, orangutan limbs have adapted to swinging through trees. Only large and older males travel on the ground, as the smaller branches in the canopy cannot support their weight. They use a clenched fist, not knuckles, to assist movement on the ground.
Orangutans are omnivores, but mostly they are herbivorous and feed on wild figs and fruit - their favourite foods, However, orangutans also eat leaves, bark, seeds, plant bulbs and tender shoots. They are also known to eat insects and small birds and mammals and drink water collected in the holes between branches, saving them having to leave the trees to look for water.
Orangutans are intelligent creatures and have been known to use objects that they find as tools. Leaves are adapted to form umbrellas, to prevent the rain from soaking them and are also used as cups to help them drink water. These techniques are passed onto their young.
Being very shy creatures orangutans are usually solitary, though during the day they may travel in small groups. Adult males tend to be totally solitary, and only stay with a mate for a few days during the mating season. Groups usually comprise two females and their young, and these mother-offspring groups stay together for the first seven years of the offspring's life. They have large territories as a result of their eating habits, which require them to have a large area from which to gather food. If too many orangutans were in the same area, starvation could result.
Every night, orangutans construct a nest in the forks of tall trees, to form an individual platform built of branches and leaves where they can sleep. Nests are shared with a mother and her offspring. They tend to nap during the afternoon after a busy morning foraging for food.
Developing orangutan males are unable to fully develop their cheek flaps while in the presence of an adult male. This means that they remain as sub-adults, both smaller in stature and in maturity. Due to their lower status, female orangutans prefer to mate with dominant (and fully mature) males. As such, it is extremely common for sub-adult males to force females into copulation for their sexual gratification.
The Classification of Orangutans
There is debate as to whether there is a further division of orangutans into two sub-species. Pongo pygmaeus pygmaeus has a round face and dark red hair, and is to be found in Borneo. Pongo pygmaeus abelii has a narrow face and is found in Sumatra. Because these groups of orangutans have been geographically separated from one another for a long time, they are now physically distinct. However, there is enough of a genetic resemblance between the groups to allow interbreeding (thus, they are by definition still members of the same species). Maybe one day these groups will have become so distinct that they cannot interbreed, and a new species will have evolved.