Orangutans 101 I chose to study orangutans because most researchers in the field of great ape intelligence had ignored them, despite hints that beneath their sluggish exteriors they are exceptionally thoughtful. But if there wasn't much information on their intelligence, there was plenty on other facets of their adaptation; efforts to study wild orangutans began in the late 1950s. The job turns out to have its easy side. Orangutans spend their time slowly and serenely meandering through the treetops, just minding their own business. Unfortunately they do it in the almost inaccessible, swamp-logged, leech-laden tropical rainforests of Borneo and Sumatra. They also, on occasion, chase researchers out of their forests. It would take humans as obstinate as orangutans themselves to brave the discomfort of that environment to study them. Fortunately, there have been some. They now number in the dozens. The great red Buddha Orangutans signature feature has to be their red-orange color. Surprisingly, that is also one of the main reasons they are hard to study, because it makes them especially difficult to find. Finding a wild orangutan makes finding a needle in a haystack look like a kindergarten task in comparison. As a hint of how hard it can be, in the late 1950s George Schaller logged only 5.75 hours of direct observation of wild orangutans, after months of work. Part of the difficulty is that orangutans come quietly, in ones and twos, way up in the canopy, half hidden in foliage. On top of that, believe it or not, their orange color lets them vanish. Many researchers, myself now included, can attest to watching an orangutan disappear right before their eyes. The explanation lies in the way sunlight penetrates the forest. Because the rainforest is so deep and dense, most sunlight that filters through the canopy does so by bouncing off vegetation. Vegetation reflects green light -- the color we see -- but absorbs red and orange. By the time sunlight has bounced down through the canopy it has been robbed of its ability to register reds and oranges. In the midst of forest vegetation or on the forest floor, orangutans become large, dull brown lumps, just like the dead wood littered everywhere. Beyond color, orangutans' most prominent feature is size. Like all great apes, orangutans are exceedingly large -- in scientific terms, they come under the heading of megafauna. Largest by far are adult males, reaching 1.25 meters tall and over 100 kilograms in weight. Their strength is legendary, reputedly seven times as great as a man's. So much larger are adult males than other orangutans that the Iban Dayak people of north Borneo call them a separate species of orangutan, the biggest of three. The other two "species" are the middle-sized and the small (the Dayaks say they never get large). The middle-sized ones would be adult females and near-adult males and females, who are close to a meter tall and 35 to 50 kilograms, about half the adult male weight. Little ones would of course be youngsters. They weigh only 1.5 to 2 kilograms at birth and remain under about 25 kilograms for six or seven years. In this phase they grow so slowly, they could seem permanently small. Their growth spurts at adolescence, at least in males, but then they change so much as to be virtually unrecognizable. Adult males also differ from other orangutans in having cheek pads. a great drooping throat pouch, long, shaggy hair that can look like dreadlocks, and a distinctive "long call." Cheek pads are subcutaneous accumulations of fibrous tissue between eyes and ears that give their faces the look of giant pieplates or blinkered horses. Peter Rodman and John Mitani have suggested they may help aim the male's long call so that it travels farther, and their visual impact -- massive size -- makes a very convincing threat. These features are likely important to orangutans' mating system, in which adult males compete for access to a precious group of females who can carry their offspring. Orangutans, like all great apes, are designed for life in the trees suspended below branches, so their arms are longer than their legs and their shoulders wider than their hips. Orangutans are the only great apes to embrace this modus operandi close to full time, travelling as well as sleeping and eating in the trees, so they have exceptionally narrow, elongated arms and hook-like hands and feet for grasping branches. The other great apes, all from Africa, tend to travel on the ground by walking quadrupedally on their knuckles. When orangutans travel terrestrially, they walk either upright or quadrupedally on their fists. Orangutans are exceptionally long-lived. The current estimate of their lifespan is thirty-five to forty years but researchers now know wild adults in their late forties at least and captives who have reached sixty. Orangutans have the longest immaturity of all the great apes, nine to twelve years. Their immaturity has three stages of roughly equal length -- infant, juvenile, and adolescent -- paced by birth, weaning, puberty, and sexual maturity. Females are deemed adult with the birth of their first infant, around fourteen to sixteen years, and males with the emergence of full adult regalia -- cheek pads, throat pouch, and long call -- as late as nineteen or twenty years. Males show an unusually prominent two-stage maturation, with adulthood preceded by a distinctive and indeterminate subadulthood stage. Male subadulthood usually starts at about ten years of age and lasts until about fifteen, but may continue until nineteen or twenty or even, very rarely, until thirty-five or forty Reproduction, correspondingly, is exceedingly slow. Orangutan females' estrus cycles average thirty (29-32) days, their pregnancies are just under nine months long (230-260 days), and they give birth to a single infant at a time. In all this they are very like human females, except for the fact that they bear an offspring only once every eight to ten years. This may contribute to the males' fierce competition for females. It also makes orangutans extremely fragile as a species: they reproduce so slowly that losses take decades, even centuries, to replace. Islands of the apes Orangutans range today only on the islands of Borneo and Sumatra. They are not spread everywhere on the two islands. Their diet, primarily fruit, makes for a marked preference for lowland alluvial and peatswamp forest habitat close to waterways. The best orangutan habitat is near coasts and rivers, because farther inland elevation rises and other forests predominate. Permanent orangutan populations are rarely found above 500 meters of elevation. Those ranging higher probably migrate to lower elevations for food for some periods of the year. Orangutans' island distribution has led biologists to recognize two subspecies. perhaps even two species, Bornean and Sumatran. Sumatran orangutans tend to have red-orange hair, often whitish around the mouth and abdomen; Borneans tend to be darker, sometimes almost chocolate. Bornean adult males tend to have more robust bodies than Sumatrans as well as larger, differently shaped cheek pads, while Sumatran males have better beards. Sumatrans seem to be more arboreal and somewhat more social than Borneans, who have a bit of a reputation for turning into grumpy old men (and women). The variability may be even greater. Borneo is the third largest island in the world, and is divided by high mountain ranges and wide rivers that, for orangutans. are as old and impassable as the straits dividing Borneo and Sumatra. Corresponding to Borneo's major geographical regions -- east, northwest, and southwest -- there may be three types of Bornean orangutan. It seems to be the easterners that tend to chocolate coloration. The southwesterners, in the region closest to Sumatra, look much like typical Sumatrans, although there may be several types of Sumatran orangutan too. Herman Rijksen detected a robust Sumatran type with lightish skin, orange-red hair, heavy build, and stubby hands and feet, often lacking nails on the thumbs and big toes, and a delicate type with darker, chocolate or maroon hair; dark, blackish skin; and delicately built, long, well-developed hands and feet with complete nails. Being orangutan Field researchers early spotted orangutans' priorities in life: eat, rest, travel, and occasionally socialize. The tempo of it all is slow, deliberate, and measured, and their acts are reflective, meticulous, and orderly. Orangutans virtually never stoop to the impulsive and reckless behavior of chimpanzees. They are among the mildest mannered primates -- gentle, laissez-faire, and normally peaceable. At the top of their priority list is food. As one expert, Biruté Galdikas, put it, the top three priorities in an orangutan's life are food, food, and food. Orangutans are frugivores, with 50 to 60 percent of their diet devoted to fruit. They consume a host of other foods as well, making a remarkably diverse menu of up to 400 different items, including young leaves, sap. flowers, honey, shoots, stems, seeds, nuts, bamboo, fungus, pith, bark, soil, termites, ants, eggs. and invertebrates. Very rarely, they hunt for small mammals. Sri Suci Utami, an Indonesian researcher, once watched an adult Sumatran female search out, pursue, kill, and eat a slow loris ( Nycticebus coucang ), a small nocturnal primate. It takes vast quantities of food to fill their huge caloric needs, so they spend, on average, half their waking day just eating. Orangutans rest a lot. It's easy to see how the story arose that they stayed mum to avoid work. They rise and retire with the sun; in the tropics, that makes for 12 hours of rest. At night. each sleeps in its own intricately woven sleeping nest of leafy branches that it builds high in the trees. Being nomadic, orangutans usually build a fresh nest in a new spot every day -- often near a good food tree that can provide the evening's dinner as well as the next day's breakfast. Even during the day they spend about 40 percent of their time resting, sometimes napping in a quickly made day nest or draped along a comfortable branch or liana. Orangutans travel over large areas of forest in search of food, each within a personal home range. Neighbors' home ranges often overlap, and adult females share their range with their pre-adolescent offspring. Bornean forests commonly support orangutans at densities of no more than one to three per square kilometer; even the richer Sumatran forests support at most six or seven orangutans per square kilometer. In Borneo, one adult female may need a home range as large as five to six square kilometers. Adult males' ranges are even larger, overlapping several female ranges. Each day orangutans normally cover only a small portion of their range, often traveling only as far and as fast as they need in order to eat. Sometimes they move as little as 200 to 300 meters and, on average, they whiz along at a third of a kilometer per hour -- one tenth the speed of a chimpanzee. Adult males travel the fastest and the farthest daily. perhaps to satisfy their gargantuan food requirements, but perhaps also to control desirable females and intruder males. Orangutan travel is almost entirely arboreal in Sumatra, where tigers still roam the forest floor. Large predators are fewer in Borneo, and there, the females normally travel in the trees, but adult males travel on the ground and climb to feed. Adult males likely travel on the ground because their weight precludes safe passage in the canopy. Like other apes, orangutans travel arboreally below branches, suspending their weight from their arms. Unlike other apes, they almost never jump or drop, and they rarely brachiate (swing by their arms from branch to branch). Instead they tree-sway or clamber their way cautiously through the canopy's tangle of branches and lianas. In treeswaying, they ride slender pole-like trees as if they were vaulting poles, sailing in great arcs through the air from one huge tree to the next, or as if they were down escalators, letting their weight bow the tree right to the ground then stepping off neatly at the bottom. In clambering, they move by using any or all four limbs to grasp supports above, below, beside, and ahead. The look is almost of walking on air, or the oozing forward of a great red amoeba. The greatest mystery surrounding orangutans is their largely solitary lifestyle. Solitude is unusual in primates, who are renowned for rich social lives. It is considered likely that orangutans have been forced into relative solitude because their enormous food needs mean that they can't afford to share. And no large predators except humans, and perhaps tigers in Sumatra, threaten adult orangutans, so they may not need groups for protection. Mature males are the most solitary. They are so intolerant of one another that if they meet, they threaten each other by staring, inflating their throat pouches, long-calling, and shaking branches. If neither backs down the face-off may escalate to hand-to-hand combat, sometimes to the death. The only contact adult males appear to enjoy is a few weeks' consorting with a sexually receptive adult female. Such interludes are not frequent because females become sexually receptive only once every eight to ten years. Even then, the male abandons his female consort within days of her becoming pregnant. Females are less solitary, even semi-social. They normally live with their offspring, making what is perhaps the only stable social unit in orangutan society. Immatures are downright gregarious. Infants stay in constant contact with their mother for most of the first year of their life, venture only meters away during their second, and travel and sleep with her until five to seven years of age, when they are weaned. Even after weaning, as juveniles, they remain semi-dependent and tend to range near their mothers. Youngsters may see little of older siblings because of the long interval between births, but they establish friendships with same-sex age-mates as juveniles. Youngsters start to move off on their own as they approach adolescence, males at around seven to eight years of age and females a bit later. Adolescent females commonly establish their own home range near their mother's. Adolescents too can establish long-term relationships, often with opposite-sex partners. Orangutan sexuality shows yet more quirks. Unlike many primates, female orangutans are willing to mate throughout their menstrual cycle and show no obvious signs of estrus. When an adult female is inclined to mate, she exercises considerable choice. She may actively seek out the particular male she desires, listening for his long calls to help locate him; then she may entice him with a host of seductive tactics, and actively stimulate his arousal. As for undesirable males, especially subadults, females just as actively spurn their advances. Persistent rebuffs may account for the fact that subadults regularly resort to forced copulations, which have been likened to rape. Thinking on the wild side It may not seem that the demands of orangutan life are very complicated -- perhaps, you are thinking, they have no need of high intelligence. That impression could be one reason orangutan intelligence has not been prominent on the field research agenda. Another reason could be that the close observation needed to study intelligence is rarely possible with wild orangutans. Most field researchers have nonetheless noticed signs of sophisticated thinking. Orangutans' tree-to-tree movement shows an exquisite understanding of how to manipulate multiple forces. Their travel routes suggest that they navigate by detailed "mental maps" which include not only the location of food sources but also the distances, routes, and obstacles between them. They have been observed to chart the shortest route to their destination from their current position. They use "traditional" travel routes, routes known and used by many individuals, suggesting some sort of culture. They seem to plan their travel routes in advance, establishing clear travel directions that take them to obvious goals. They may also detour from their current route to reach a known food tree, check its crop and, if they find it not ready, backtrack to their original route. Feeding may also require high intelligence because some orangutan foods, such as coconuts and spiny durian fruit, are very difficult to obtain. Orangutans have been seen to use very complex techniques to extract such foods despite the plants' apparently impregnable defenses. But this ties in with one of the great black marks against orangutan intellect: wild orangutans, unlike their chimpanzee cousins, rarely use tools to gain access to difficult foods. Understandably, then, most scientists interested in studying orangutan minds have turned away from wild orangutans in favor of captives. Interest in nonhuman primates perked up enough in the late 1950S and 1960s to spawn a few studies of orangutan intellect, even though orangutans had been sidelined since the turn of the century, when chimpanzees took center stage. In these studies, orangutans repeatedly demonstrated the mechanical genius that had so impressed Yerkes, mastering tools of exceptional sophistication and solving complex physical puzzles. One mastered making stone flake tools, which he used for cutting. Another tackled a complex locks-and-boxes task. He was presented with five boxes, one of which held keys to the other four. Of the four locked boxes, one held food, one was empty, and two held keys -- one of which would unlock the food box. To get the food, he had to select the right key from the first box -- the key to the box with the key to the food box, unlock that box, take that key, then unlock the food box. He breezed through the test. Orangutans seem to solve some of these problems by insight, that is, by thinking, rather than by trial-and-error fiddling. Orangutans also (again) showed capacities for language, lying, planning, and imitation. One famous orangutan, Chantek, did everything. For eight years, starting in 1978 when Chantek was nine months old, anthropologist Lyn Miles tutored him in the American Sign Language for the deaf. Great apes are incapable of speaking but have been apt pupils of sign language. a language of gestures. Lyn deliberately immersed Chantek in the world they talked about to give him the same advantages as a human child learning language. That world was Chattanooga, Tennessee. So Chantek went to fast food joints, ate hamburgers, chose his own ice cream flavor, had chores like cleaning his room, and got an allowance for doing them. He learned more than 150 signs, and he made and understood short sentences, rivalling the accomplishments of bonobos and chimpanzees. He lied about three times a week, mostly to get into the bathroom. He'd sign "dirty," meaning he needed the toilet, but once in the bathroom he just wanted to play and wouldn't use the toilet at all. He recognized himself in mirrors. He even liked to check out new "looks" in mirrors, for example, how he looked in sunglasses. He planned, signing "in milk raisin" to himself before heading into his trailer and asking a caregiver for "milk" And he imitated: he curled his eyelashes at the mirror with his caregiver's eyelash curler, just as she did, and he cooked things -- like his cereal, which he put into a pot, then onto the stove, and his camera, which he put into a pot of water. These studies put orangutan minds on a par with the minds of other great apes, maybe even beyond. Many of their accomplishments -- insight, tool use, self-awareness, language, planning, imitation -- are on the reasoning side of Aristotle's Rubicon. Some scholars discount these accomplishments as illusions, the artificial products of unsound research. They argue that great apes accomplish these feats only with extensive human support, so what is shown is the power of human culture, not the power of apes' minds. But you could just as easily argue that these findings underrepresent apes' abilities. Great apes' lives in captivity are more often marked by deprivation than by enrichment. And most findings come from experimenter-planned tests and command performances that are probably about as inspiring as having to play the piano for family guests. What we are seeing, in fact, is that great apes' abilities are better than what the studies of captive subjects have shown. The most recent evidence, from Carel van Schaik, is that wild orangutans make and use tools to obtain some difficult foods. The curious thing is that virtually all independently foraging members do so in the community he studied, Suaq Balimbing in Sumatra. What's more, the Suaq orangutans use tools to obtain a food, Neesia fruit seeds, that orangutans in other communities obtain without tools. Researchers see this as a cultural tradition, and so we now face the paradoxical situation that the orangutan, the solitary ape. has solid credentials for membership in the culture club. And orangutan cultures are comparable in complexity and scope to those of chimpanzees. This brings us full circle back to intelligence, because it takes just as sophisticated a mind to learn how to make and use tools from companions as it does to master these skills independently. Personal Pickle What I wanted was to study orangutan minds functioning at their peak, and that put me in a bit of a pickle. Ideally, wild orangutans in their natural setting would be my best bet; only there would I be able to watch them coming to grips with the real intellectual problems they and their ancestors had been dealing with for millennia. However, their lifestyle makes the close-up, fly-on-the-wall view I needed almost impossible. Captives, on the other hand, are accessible but often emotionally and mentally troubled as a result of human treatment, and thus unlikely to function at their best. On top of that, there are few bridges between these two forms of intelligence -- the first developed to handle the problems of rainforest life, the second to handle a rarefied set of human-defined situations. What I needed was orangutans who could help me bridge this gap. by bridging it themselves. And I found them, although I didn't appreciate the richness of my find at first. The orangutans I had come to Camp Leakey to study were ex-captive orangutans under rehabilitation to free forest life, and thus belonged to a third, intermediate category. What I knew of them was they had been captured illegally to feed the lucrative trade in live animals, to be kept as pets or sold. Any captured orangutans that are located by the authorities are confiscated and turned over to special sanctuaries in Borneo and Sumatra for rehabilitation to free forest life. I thought these rehabilitants might have the qualities I sought: they would be familiar enough with humans to tolerate close observation, and knowledgeable enough about human customs to act in ways I could comprehend. They had also been released from the deprivations and frustrations of captivity so I expected to be able to observe involved, active, functioning individuals rather than bored, depressed, or abused ones. And in the sanctuary environment they would be free to develop their abilities in tune with their own interests and the world in which they were designed to live. These were my hopes, and as it turned out my expectations were correct. Little had been written about rehabilitant orangutans. There has been a tendency to dismiss them as damaged goods, no longer "pure" wild orangutans but oddball nutcases, fit only for the odd anecdote or the education of visitors. One of the few serious reports I found came from Camp Leakey. the center in southcentral Borneo run by Biruté Galdikas. Galdikas is a well-known Canadian, a pioneer in the study of wild orangutans and the third of the three women "angels" that Louis Leakey sponsored to promote the study of free-living great apes. Like Jane Goodall's work with chimpanzees and Dian Fossey's with mountain gorillas, Galdikas's work with orangutans became a lifetime project. She had been studying wild orangutans since the early 1970s and rehabilitating ex-captives for almost as long. Her articles described rehabilitants as great tool users and suggested they learned by imitation, the ability that interested me most. And that was how I came to be on board a kelotok in August 1988, heading upriver into the rainforests of Borneo. Excerpted from Orangutans: Wizards of the Rain Forest by Anne E. Russon All rights reserved by the original copyright owners. Excerpts are provided for display purposes only and may not be reproduced, reprinted or distributed without the written permission of the publisher.
