Bornean orangutan - Ecology & Habitat

High quality habitat critical to birth-rate

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. The age of first reproduction in the Borneo orangutan is around 10-15 years of age, but there may be differences between the various sub-species.

Breeding
Orangutans usually give birth to a single young, or occasionally twins, probably not more than once every five years. For the Bornean orangutan, the inter-birth 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.