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The shy and solitary orangutan is second only to the gorilla in size among the primates. Found solely on the island of Borneo and Sumatra, its population has decreased drastically. Of the three great apes, the orangutan, the chimpanzee, and the gorilla, the orangutan is the only one to live outside Africa. Hidden in the dense, tropical rainforests that are its home, it is also unique among apes for being truly forest dwelling.

The orangutan lives a solitary life in the treetops of the rainforest. With the exception of adult males, orangutans rarely descend to the ground. At night, females and youngsters sleep in a nest of branches placed in the fork of a tree. Because males are heavier, they generally prefer to sleep on the ground. At daybreak, orangutans leave their nests and go searching for food. Orangutans are far less sociable than other apes, and do not live in large social groups. Adult males are particularly solitary, and stake out areas of forest that they defend as their own territories, fighting other males who intrude, if necessary. Females occasionally group together loosely with their young.

Fruits, nuts, leaves, bark, insects, and eggs form the diet of an orangutan. When the food supply in a particular area is plentiful, an orangutan may remain in one place for a period of time to feed. Orangutans, like the other apes, appear to be highly intelligent. The can memorize the geography of their surroundings and will travel great distances to find trees that have ripe fruit. When orangutans are thirsty, they locate a hollow in a tree where water has collected from past rainstorms.

A dominant male orangutan may have a large breeding territory and mate with several females. Mating occurs year round and females give birth to a single offspring every three to six years. A baby orangutan grows very slowly. It may become somewhat independent at three years of age, but it will stay with its mother until she gives birth again. Because female orangutans do not mate again until an offspring is at least 3 years old, they may only succeed in raising two to three young in a lifetime.

The orangutan poses no threat to man, yet man is its only enemy. The orangutan’s natural habitat has been destroyed to provide land and timber for an increasing human population. Female orangutans are slaughtered so that their babies can be captured for zoos. The babies often die in captivity. Since its breeding rate is relatively slow, its numbers have not recovered and it is a seriously endangered species.