Native to Indonesia and Malaysia, orangutans (Pongo pygmaeus and Pongo abelii) are found only on the islands of Borneo and Sumatra. Their name derives from the Malay and Indonesian phrase ‘orang hutan’, meaning ‘person of the forest’. Orangutans spend most of their time in trees, and live a more solitary lifestyle than the African great apes. Social bonds occur primarily between mothers and their offspring, who stay together until adolescence. Fruit makes up about 60% of an orangutan’s diet; other food items include young leaves, shoots, seeds, bark, insects, and bird eggs. Orangutans use a variety of sophisticated tools and construct elaborate sleeping nests each night from branches and foliage.
Two species of orangutan are recognized: the Bornean orangutan and the Sumatran orangutan.
SOUTHWEST BORNEAN ORANGUTAN (P. P. WURMBII)
SUMATRAN ORANGUTAN (PONGO ABELII)
TAPANULI ORANGUTAN (PONGO TAPANULIENSIS)
GRASP & IUCN (2018). Report to the CITES Standing Committee on the Status of Great Apes. UN Environment, Great Apes Survival Partnership, Nairobi and International Union for Conservation of Nature, Gland.
Orangutans are mostly covered with long, reddish-brown hair and grey-black skin. An orangutan has a large, bulky body, a thick neck, very long, strong arms, short, bowed legs, and a large head with a prominent mouth area. Though largely hairless, their faces can develop some hair in males, giving them a mustache.
Adult males have large cheek flaps to show their dominance to other males. Sumatran orangutans have lighter hair and a longer beard than their Bornean relatives, and Sumatran males have narrower cheekpads. Mature males’ throat pouches allow them to make loud long calls to attract females and intimidate rivals. The joint and tendon arrangement in orangutans’ hands is adapted to arboreal locomotion.
Flanged adult male orangutans can reach 175 cm (5.7 ft) in height and weigh over 118 kg (260 lb), while females can grow up to 127 cm (4.2 ft) and weigh around 45 kg (99 lb).
The Bornean orangutan is endemic to the island of Borneo where it is present in the Malaysian states of Sabah and Sarawak, as well as in Kalimantan (Indonesian Borneo). Species distribution is now highly patchy throughout the island: it is apparently absent or uncommon in the south-east of the island, as well as in the forests between the Rejang River in central Sarawak and the Padas River in western Sabah. Distribution for each subspecies is as follows.
The northeast Bornean orangutan is present in East Kalimantan and Sabah.
The northwest Bornean orangutan is present in north-western Kalimantan from north of the Kapuas River to north-eastern Sarawak.
The central Bornean orangutan is present in West Kalimantan south of the Kapuas River and Central Kalimantan west of the Barito River.
Male orangutans mature at around 15 years of age, by which time they have fully descended testicles and can reproduce. Females give birth to their first offspring at 14-15 years of age, after a gestation period of about 9 months. Intervals between births are 7 to 8 years, the longest birth intervals among the great apes, and a female has usually no more than 3 offspring in her lifetime. This means that orangutan populations grow very slowly, and take a long time to recover from habitat disturbance and hunting.
Raising the young is done mostly by the females, and infants remain dependent on their mothers for at least 5 years. Completely dependent on their mothers for the first 2 years of their lives, juvenile orangutans (2-5 years of age) increasingly move away from their mothers. Orangutans are usually weaned at about 4 years of age. An orangutan’s lifespan in the wild is about 35-40 years.
VIRTUAL ECOTOURISM
Ecotourism lends a hand at Bukit Lawang. Tag along with a group of ecotourists as they visit a feeding platform at the orangutan rehabilitation center near Bukit Lawang.
Rescued Apes find Solace. Take a tour of the Sumatran Orangutan Conservation Program’s (SOCP) quarantine facility, where rescued apes are monitored and cared for while the SOCP lobbies and raises funds for more permanent shelter.
Tripa’s Emperilled Peat Swamps. Join Ian Redmond 30 feet in the air for an ape’s eye-view of the rapidly disappearing habitat of the critically endangered Sumatran orangutan.
OTHER GREAT APES
BONOBOS
Bonobos (Pan paniscus) are largely peaceful, frugivorous great apes found only in DR Congo that live in highly complex, fission-fusion societies.
CHIMPANZEES
Chimpanzees (Pan troglodytes) can be found from southern Senegal across the forested belt north of the Congo River to western Uganda and western Tanzania.
GORILLAS
Gorillas (Gorilla gorilla and Gorilla beringei) are ground-dwelling apes occupying a variety of different habitats and elevations in central African forests.