Around the sun leaving a bright trail behind. For more than

More than 20 years later, Galdikas, now 46, is still following that advice. In a remote peat swamp forest of Kalimantan, the Indonesian part of the island of Borneo, she is conducting the longest study of wild orangutans ever undertaken. The youngest of Leakey's so-called trimates, the trio of women he picked to help plumb the origins of humanity's special nature, Galdikas has shed new light on the social patterns of the orangutan, literally ^tman of the forest' in Malay, one of our closest relatives.

In the process, she has endured malaria, typhoid, dengue fever and skin bums from toxic tree sap. Like Fossey, who was murdered in 1985, Galdikas has been led, through her scientific work, to campaign for the protection of the endangered apes and their dwindling rain-forest habitat. Only 30,000 to 50,000 orangutans remain in Borneo and Sumatra. Galdikas' advocacy put her at odds with Indonesian authorities, who at one point threatened to end her work.

Long-lived and highly intelligent, orangutans dwell and travel high in the rain-forest canopy, revealing themselves only to the dedicated. As a result of her years in a 40-sq-km study area in the Tanjung Puting National Park, Galdikas has been able to follow individuals from infancy. She has learned that the orangutans there have their first offspring at the age of 16. Subsequent births, always a single infant, come every eight years, the longest birth interval of any known wild species. Zoo orangutans reproduce much faster. If her findings are true for all wild populations, she says, "orangutans are much more vulnerable to extinction than anyone thought."

Experts believed that big male orangutans fight with one another, but no modern scientist had seen a battle Until Galdikas, who waited months for such a confrontation. "At the end there was blood and tufts of hair all over the forest floor," she says. But the battle was broken off well short of permanent injury or death. A solitary creature, the orangutan does not live in groups or families like other great apes. But she has found indications of a

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subtle social system: at times adolescent males and females travel together without mating, almost as friends, evidence that one of our closest relatives is not completely asocial.

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THE LONG HABIT