The orangutan (Pongo pygmaeus), one of the Old World great apes, has its population restricted to the rain forests of the Indonesian islands of Sumatra and Borneo. The orangutan is the largest living arboreal mammal, and it spends most of the daylight hours moving slowly and deliberately through the forest canopy in search of food. Sixty percent of their diet consists of fruit, and the remainder is composed of young leaves and shoots, tree bark, mineralrich soil, and insects. Orangutans are long-lived, with many individuals reaching between 50 and 60 years of age in the wild. These large, chestnut-colored, long-haired apes are facing possible extinction from two different causes: habitat destruction and the wild animal trade.

An orangutan. (Photograph by Tim Davis. Photo Researchers Inc. Reproduced by permission.)

The rain forest ecosystem on the islands of Sumatra and Borneo is rapidly disappearing. Sumatra loses 370 mi² (960 km²) of forest a year...