Orangutans live wild only on the islands of Borneo and Sumatra. The two populations have been isolated for more than a million years and are considered separate species; the Bornean orangutans are slightly larger than the Sumatran variety. Precious little was known about orangutan biology before Galdikas started studying it. She has discovered that the tree-dwelling animals spend as much as half the day on the ground. Adult males can reach five feet tall (though they rarely stand erect) and weigh up to 300 pounds. "They're massive," says Galdikas. "That's what you notice more than height." Females weigh about half as much and are four feet tall. Both sexes can live 30 to 50 years. At night they sleep in nests of sticks they build high in the treetops.
Galdikas also has documented that the orangs of Tanjung Puting National Park procreate about once every eight years, the longest birth interval of any wild mammal. "One of the reasons orangutans are so vulnerable is because they are not rabbits that can have a few litters every year," she says. After an eight-month pregnancy, females bear a single infant, which will remain with its mother for eight or nine years.
Galdikas has cataloged about 400 types of fruit, flowers, bark, leaves and insects that wild orangutans eat. They even like termites. Males usually search for food alone, while females bring along one or two of their offspring. Orangs have a keen sense of where the good stuff can be found. "I was in the forest once, following a wild orangutan female, and I knew we were about two kilometers from a durian tree that was fruiting," Galdikas says on the front porch of her bungalow at Camp Leakey. "Right there, I was able to predict that she was heading for that tree. And she traveled in a straight line, not meandering at all until she reached the tree."
Males are frighteningly unpredictable. Galdikas recalls one who picked up her front porch bench and hurled it like a missile. "It's not that they're malicious," Galdikas assures me, gesturing toward the old bench. "It's just that their testosterone surge will explode and they can be very dangerous, inadvertently." She adds, perhaps as a warning that I shouldn't get too chummy with Tom and Kusasi, "if that bench had hit somebody on the head, that person would have been maimed for life."
She also has made discoveries about how males communicate with one another. While it was known that they use their throat pouches to make bellowing "long calls," signaling their presence to females and asserting their dominance (real or imagined) to other males, she discerned a call reserved especially for fellow males; roughly translated, this "fast call" says: I know you're out there and I'm ready to fight you.
Along the way, Galdikas has published her findings in four books and dozens of other publications, both scientific and general interest; signed on as a professor at Simon Fraser University in British Columbia (she spends about half the year in Canada and the United States); and mentored hundreds of aspiring scientists, such as the four students from Scotland's University of Aberdeen who are at Camp Leakey during my visit. Their mission? To collect orangutan feces samples to trace paternity and measure the reproductive success of various males.
I ask Galdikas which orangutan riddles she has yet to solve. "For me," she says, "the big, abiding mystery is: How far did the original males travel here in Tanjung Puting, and where did they come from?" She may never know. The 6,000 remaining orangutans can no longer travel at will because of palm oil plantations surrounding the park, all created since 1971. When she began the study, she says, "orangutans could wander to the other side of Borneo if they felt like it. Now they're trapped. They get lost in these palm oil plantations and they get killed."
Galdikas says the killings are usually carried out by plantation workers who consider the animals pests, by local people who eat their meat and by poachers who slaughter females to capture their babies, which are then sold illegally as pets.
As recently as 1900, more than 300,000 orangutans roamed freely across the jungles of Southeast Asia and southern China. Today an estimated 48,000 orangutans live in Borneo and another 6,500 in Sumatra. Galdikas blames people for their decline: "I mean, orangutans are tough," she says. "They're flexible. They're intelligent. They're adaptable. They can be on the ground. They can be in the canopy. I mean, they are basically big enough to not really have to worry about predators with the possible exception of tigers, maybe snow leopards. So if there were no people around, orangutans would be doing extremely well."
To grow oil palm (Elaesis guineensis) in a peat swamp forest, workers typically drain the land, chop down the trees (which are sold for timber) and burn what's left. It's a procedure, Galdikas says, that not only has killed or displaced thousands of orangutans but also has triggered massive fires and sent huge amounts of carbon dioxide into the air, furthering climate change.