On average, they survive about 45 years and are notoriously solitary, though females in the wild are often accompanied by their young. Adolescent females and males also often travel together. The apes spend most of their day in search of food, sometimes descending from the canopy for brief feeding forays on the ground. Their diet consists mainly of fruit, as well as certain types of leaves, bark, flowers and insects. At night, they build nests in which to sleep.
Orangutans give birth only once every eight or nine years.
The young remain close to their mothers until the age of six or seven. As forest habitat has dwindled and become criss-crossed by mining and logging roads, orangutans have become increasingly vulnerable. A 1993 survey by IUCN-The World Conservation Union indicated that suitable orangutan habitat in Indonesia and Malaysia has declined by more than 80 percent in the past 20 years, dropping the total orangutan population to between 10,000 and 16,000 in Borneo and between 7,000 and 12,000 in Sumatra. Shrinking habitat means more than simply less food and shelter for the red apes. It was in response to a surge in hunting that Herman Rijksen, a Dutch primatologist, opened the first orangutan rehabilitation center in Indonesian Sumatra, at Ketambe in 1971.