Photograph by Patrik Stollarz/AFP/Getty

In 1990, while visiting a research camp in central Borneo, the primatologist Anne Russon saw an orangutan nicknamed Supinah attempt to make fire. Supinah sauntered toward an ashy fire pit, picked up a stick glowing with embers, and dipped it into a nearby cup full of liquid. Russon thought that the cup contained water, but it in fact held kerosene. Fortunately, that bath did little more than dampen the wood. Yet Supinah persisted: she got a second glowing stick, blew on it, fanned it with her hands, and rubbed it against other sticks. She never got the right steps in the right order to start a fire, but what foiled her was not her innate intelligence. She had a clear goal in mind and the right kind of brain to achieve it. She just needed a little more practice.

At the time, Russon was visiting Camp Leakey, which the anthropologist Biruté Galdikas established, in 1971, to study orangutans, just as Jane Goodall and Dian Fossey had done, in Africa, to observe chimpanzees and gorillas, respectively. Since then, Galdikas, Russon, and a handful of other orangutan specialists have learned firsthand just how intelligent and resourceful the animals really are. Some of their mental skills may exceed those of their great-ape brethren. Michelle Desilets, executive director of the Orangutan Land Trust, has summarized the unique intellect of orangutans like this: “They say that if you give a chimpanzee a screwdriver, he’ll break it; if you give a gorilla a screwdriver, he’ll toss it over his shoulder; but if you give an orangutan a screwdriver, he’ll open up his cage and walk away.”

Compared with chimpanzees, which are highly excitable, orangutans seem far more sober and considerate. They move deliberately and often spend a good deal of time silently watching before deciding how to act. At Camp Leakey, the orangutans had plenty of opportunity to observe and imitate people. They soon developed a habit of stealing canoes, paddling them downriver, and abandoning them at their destinations. Even triple and quadruple knots in the ropes securing the canoes to the dock did not deter the apes. Over the years, they have also learned to brush their teeth, bathe themselves, wash clothes, weed pathways, wield saws and hammers, and soak rags in water in order to cool their foreheads with them. And they have done all of this without any instruction.

For a time, the deftness of orangutans living near people was puzzling, because they did not seem to display such acumen on their own in the wild. More careful observation revealed otherwise. Scientists now know that wild orangutans use sticks to search for ants under tree bark, make hats and umbrellas out of large leaves, and sometimes drape themselves with lianas—forest vines—as if donning necklaces. When they need to cross a river that is too deep to ford safely, some orangutans bend saplings into bridges and twist several tree-anchored vines into a rope for extra support.

In 2004, Russon and her colleagues, along with a crew from Animal Planet, began documenting another intriguing behavior. That year, Russon saw a young male orangutan pick up and eat a dying catfish stranded on the bank of a dwindling river. By 2007, Russon and Animal Planet had noted forty other instances of similar behavior. The apes pulled fish out of shallow ponds by their tails or pursued them into deeper water. One orangutan even attempted to skewer a fish with a large stick, scaring it onto land. Although baboons and other primates have been observed catching fish, these are the only great apes currently known to systematically hunt and eat fish.

In orangutans—as in chimpanzees, dolphins, and a few other species—a penchant for tool use and problem-solving has brought about cultural learning, in which animals teach one another new behaviors, transmitting the information among members of a group, sometimes from one generation to the next. Culture is what gives different groups of the same species distinct ways of achieving the same goal. In one experiment, conducted at a rehabilitation center in Sumatra, researchers found that nine of the thirteen orangutans from swampy regions of the island knew how to use a stick to extract honey from a hole in a log. By contrast, only two of the ten from coastal regions could do the same—the only two that had been living at the rehabilitation center long enough to learn the trick from the swamp natives.

At first, the idea of widespread social learning among orangutans was at odds with traditional depictions of the ginger apes as loners. Researchers had long assumed that the mother-infant pair was the only unit of orangutan social structure. But it turns out that adult female relatives stick together: they have overlapping ranges and periodically interact. “I grew up in rural Saskatchewan,” Russon, who now works and teaches at York University, in Toronto, told me. “And, for me, that is exactly what orangutan social life is like. There are communities, but they are very broadly dispersed. It might be fifteen miles to your cousin’s place, or another twenty miles to the next nearest relative, but everybody knows everybody.” Adolescent orangutans—curious and audacious—regularly make new friends. These wandering youngsters, vaulting from one tree to the next, are likely the torchbearers of orangutan culture.

If adolescence is a period of great intellectual discovery for orangutans, it is also a time of acute vulnerability. Poachers routinely kill protective orangutan mothers, kidnap the juveniles, and sell them to disreputable zoos or traders on the illegal pet market. Such abductions have long been a serious threat to orangutans, but even more pressing is the wanton destruction of their habitat. Orangutans once lived throughout Southeast Asia. Today, they are restricted to the islands of Borneo and Sumatra. The rainforests they inhabit are constantly harvested for timber or slashed and burned to make way for palm plantations. Among the slowest of the apes, orangutans are often trapped in the inferno.

At the turn of the twentieth century, wild orangutans numbered perhaps three hundred thousand strong. The International Union for Conservation of Nature, citing data from the early and mid-two-thousands, says that Borneo’s present orangutan population consists of between forty-five thousand and sixty-nine thousand individuals, and that Sumatra has a mere seventy-three hundred. Considering that habitat destruction has been especially rampant in the past decade, however, the Orangutan Conservancy estimates that there are only forty thousand wild orangutans left alive today.

Clear evidence of sentience is by no means the only reason to rescue a creature from extinction. Still, the fact that orangutans are self-aware, that they are capable of reason and cultural learning, that they possess a manual dexterity and an intelligence undeniably similar to our own, makes the way we have treated them all the more abominable. The word “orangutan” comes from a seventeenth-century Malay expression meaning “forest person.” Perhaps it’s time we learned again to see the person in the ape.