Orangutans - Ecology & Habitat

The largest tree-living mammal in the world

The species is found in primary and secondary forest, usually lowland dipterocarp, freshwater and peat swamp forests.

Social Structure
Adult orangutans are generally solitary, although temporary aggregations are occasionally formed. The large home ranges of males overlap the ranges of several adult females. Adult males are generally hostile to one another, although they do not display territoriality.

Life Cycle
After weaning at about 3.5 years of age, young individuals become gradually independent of their mother after she gives birth to a second young. For the Sumatran orangutan, the youngest females to reproduce are 10-11 years of age, but the average age of reproduction is around 15 years of age. Similarly for the Borneo species, age of first reproduction is around 10-15 years of age, and there may be differences between the various sub-species of Borneo orangutan.

Breeding
Orangutans usually give birth to a single young, or occasionally twins, probably not more than once every five years. The interbirth interval for Sumatran orangutans has been found to be as short as 6 years and as long as 10. For the Borneo orangutan, the interbirth interval can be as low as 5 years in high quality habitats.

The long period taken to reach sexual maturity, the long interbirth periods and the fact that orangutans normally give birth to just a single young mean that orangutans have an extremely slow reproductive rate. This makes orangutan populations highly vulnerable to excessive mortality, and means that populations take a long time to recover from population declines.

Diet
About 60% of the orangutan's diet includes fruit (e.g. durians, jackfruit, lychees, mangosteens, mangoes and figs), while the rest comprises young leaves and shoots, insects, soil, tree bark, woody lianas, and occasionally eggs and small vertebrates. They obtain water not only from fruit, but also from tree holes.