The orangutan is indigenous in the rainforests of Sumatra and Borneo. Each island has its own species. The orangutan on Borneo (pongo pygmaeus) has darker brown hair and the body is more sturdy compared to the Orang utan on Sumatra,(pongo abelii). The Borneo orangutan can be divided into three subspecies: the Northwestern, Northeastern and Central Borneo type.
The orangutan mainly lives in dipterocarp forests and peat forests. Due to the convenient geographical location of these forests (and the high commercial value) most of them are threatened by deforestation in order to replace them by vast palm oil plantations.
As a result of big-scale deforestation during the last century the habitat of the orangutan has become diminished drastically. Today about 80% of the former available living area of the animals has been destroyed and has vanished.
It is in the forest canopy the orangutan spends most of their lifetime. They live on a diet of fruit , leaves and insects. The weight of a female is about 37 kilos, a male can weigh up to 83 kilos. The orangutan is the largest tree-dwelling animals.
Orangutans are solitary animals. Most of the time they spend on their own. Nevertheless, sometimes a couple of females are sighted together in one tree. In contrast, males are extremely territorial and do not accept any other male nearby. However, the territory of a male can overlap and match with those of different females.
A sexual mature male sometimes develops cheek pads, which they use to overawe other males. Females are sexually mature at the age of twelve. The gestation period of the orangutan is nine months. Usually, a female gives birth to one young.
The offspring is born in nests high up in the trees, where they are safe for predators. The first few months the young will not lose hold of its mother and during that time there is continuous physical contact between them. During the first two years, the young fully depends on its mother for its survival. Between the age of two and five, the young orangutan learns all the necessary skill to survive in the wild. The physical bond with its mother loosens and the young orangutan starts to hang out with peers. As it is growing up, the orangutan become more solitary.
During her lifetime a female orangutan gives birth to an average of 2 to 3 young. These babies do not always survive their childhood years. The timespan between pregnancies is about 8 years. Their slow reproduction cycle makes the threatened orangutanvextra vulnerable to extinction.
Ecological role in the rainforest
Due to and because of their preference of fruit in combination with the long distances they travel across the forest canopy, orangutans play an important role in spreading seeds throughout the forest.
The plant life of the forests flourish and some only exist thanks to the spreading of seed by the orangutan. This animal sustains the high standard of biodiversity in the forest.
Orangutans are an indicator of the ecological standard and ‘health’ of the forests. Moreover by fulfilling this role these animals provide researchers with important , specific facts about the function and survival of the forest.
The number of animals maintaining independence in specific regions, gives researchers vital information about the health of the area.(WWF,2012)
The Orang utan is an endangered species. The number of remaining animals differ widely. The IUCN(International Union for the Conservation of Nature) mentions about 45.000-69.000 in the years 2000-2003.
There is valid reason to predict a rapid diminishing of numbers if one looks at the years after this period. If the population decrease is continuing at this speed, there is a reasonable expectation of complete extinction within years. The biggest threats being deforestation, fragmentation, illegal trade and hunting.
Deforestation, which also is observed around the region of Tembak, is primarily caused by the palm oil industry. Companies and corporations exploit the ground for the construction of roads and cut big swathes throughout the forest; by doing this they are causing fragmentation of the area. This way they are creating islands of forest, and these islands are too small to keep the Orang utan population healthy. This situation is not favourable and is an obstacle for orangutan reproduction.
In some parts of South East Asia young orangutans are still kept as favourite “house pets”. This also is the case on Borneo. The youngsters have been caught after their mothers have been killed. The hunting mostly occurs in areas where due to deforestation there is lack of space and shortage of food for the animals. It results in confrontation between non-traditional villagers, often communities that have undergone government reallocation and have no ties to the forest and orangutans while searching for food. Because of this alienation from the forest and lack of understanding of the value of the Orang utan a lot of animals loose their lives. About 1950-3100 are estimated to be killed yearly.
Trading in orangutans is prohibited by law. Yet each year about 300 young animals are sold.(Stiles, D. Redmond, I., Cress,D., Nellemann, C., Formo,R.K.(eds) 2013.) An yearly average of 150 animals which have been traced and found in the hands of traders and will never be able to be released and live in the wild.
In the vicinity of Sintang there are approximately 70 Orang utans living in captivity with people in their homes. The regional division of Indonesian Forest maintenance (BKSDA) is investigating the whereabouts of these animals in order to bring them to SOC.