Intelligent tool use, it has been proposed, should not involve the use of the same tool behavior for every dilemma. It’s said that if the only tool you have is a hammer, every problem looks like a nail. (Readers who are capuchin monkeys should think hard about this saying, as we shall see later.) That doesn’t count as intelligent tool use. Parker and Gibson have very demandingly said that intelligent tool use “involves trial and error application of several complex object manipulation schemata such as aimed throwing, using a lever, banging with a tool, raking in with a stick, probing with a stick, in different contexts, such as opening objects, raking in out-of-reach objects, extracting objects from a container without opening it, using a variety of objects such as sticks, rocks, leaves. Intelligent tool use involves accommodation to the specific situation and exploring and manipulating physical causality.”
Gorillas
Wild gorillas do not seem to be tool users. But captive gorillas use tools readily. Richard Byrne suggests that this paradox may be understood by the complex manipulations gorillas use to eat thorny, prickly, armored, sticky, and otherwise forbidding foods in their environment.
A captive gorilla child, Alafia, gazed at a moth fluttering around the gorilla enclosure, which repeatedly landed on the same wall, too high for her to reach. She swatted at the moth, but it really was too high. Turning away, she searched through a pile of hay in the enclosure until she found a short, stout stick, which she tucked under her arm as she went on searching. Finding a longer, skinnier stick, she went over to the wall and propped the short stick against it. She stood on the short stick, whacked the moth with the long stick, and when it fell, jumped down, grabbed it, and ate it. “She let out deep grunts of satisfaction as she mashed the moth around in her mouth and over her tongue, savoring what she must have considered a rare treat,” writes gorilla ethnographer Dawn Prince-Hughes.
On another occasion, Prince-Hughes saw Alafia’s 10-year-old brother Zuri limping around the enclosure, favoring his left foot. As she watched, Zuri collected short sticks into a pile. Then he pulled a thorn off a hawthorn branch, propped his left foot up on the stick pile, and prodded with the thorn at his big toe. Finally he pulled a splinter out with his thumb and forefinger.
Three eight-year-old gorillas in the San Diego Wild Animal Park used sticks to get leaves and seeds out of trees in their enclosure. These trees were protected with electrified wiring, so the gorillas couldn’t climb them. Instead Milt, PD, and Penny tossed sticks up into the branches to knock down the mildly desirable foliage. If one stick didn’t work, they selected a bigger stick. PD and Penny also used long sticks to draw branches down so they could grab them with their other hand. Penny was seen using a long stick to beat on a branch so foliage would fall off. The gorillas first threw sticks into the trees in 1996, when they were seven. By the next year Penny and PD had improved their accuracy, but Milt, who didn’t practice, hadn’t gotten better.
Bonobos
Wild bonobos, still little-studied, haven’t been seen cracking nuts between stones. But they make rain hats. Living in the rain forest, they get rained on a lot. Rain hats are small leafy branches that the bonobo bends or places over its head and shoulders. This “may seem like a fairly simple, mundane sort of activity,” writes researcher Ellen Ingmanson, but more is involved than one might think. First the animal needs to have the concept of constructing a covering. Not all bonobos do, and neither chimpanzees nor gorillas seem to. Then the ape has to select materials, arrange them effectively, and “behav[e] appropriately in conjunction with the rain hat.”
About half of the bonobos Ingmanson watched at Wamba, Zaire, used rain hats. To the extent relationships were known, rain hat technology passed from mother to child. If a mother made rain hats, so did her children when they were old enough, and if she didn’t, none of her children did.
Ingmanson watched seven-year-old Senta give it a go during one downpour. He was sitting in a small tree several yards up when rain began falling. He started to bend branches over, and he chose fine leafy branches, good for deflecting rain. But he bent branches at waist level instead of over his head and shoulders (probably because they were more convenient to reach), and after half an hour he had done a splendid job of covering his knees, but his head was still unprotected. “Senta…appeared somewhat perplexed.” As it happened, his mother and four other females were sitting directly below him, benefiting from the rain-repellent lap blanket he had crafted. Three years later, Senta was seen making an excellent rain hat.
Orangutans
As with gorillas and bonobos, scientists have complained that it makes no sense that orangutans do not use tools in the wild and yet in captivity are adept. But in 1996, Carel van Schaik and E. A. Fox reported on a tool-using group of wild orangutans living in the Suaq Balimbang area of Sumatra, in freshwater and peat swamp forests. These orangutans are unusually easygoing and gregarious. They don’t mind if others look over their shoulders and rip off their tool-using secrets. They strip slender branches to poke into the holes of termites, bees, and ants, to “prompt” them to exit and be eaten. Sometimes they bite the tip of the stick to flatten or fray it. Usually they hold these sticks in their mouths, manipulating them with their dexterous lips, but occasionally they hold them in their hands. They use sticks as chisels to chip off pieces of termite nests. They dip sticks into stingless bee nests to get honey. And they use sticks to deal with Neesia fruit. Although Neesia fruit contain delicious nutritious seeds, these are embedded in irritating hairs. A ripe Neesia, when it has cracked open, presents the problem of how to get the seeds without being stung by the hairs. The orangutan solution is to insert a stick into the crack in the fruit and scrape out the hairs. Then you blow the hairs off the stick, use the stick to push the seeds toward the apex of the Neesia, and scoop out the seeds with the stick or your finger.
(That tolerance and respect are relevant to the use of expertise is shown by the rhesus macaques of Cayo Santiago. They love coconut, but the only two monkeys who knew how to crack coconuts, by strategic flinging, gave up the habit. WK knew how, and so did his little brother, 436. When they lived in the troop where they were born, they were under the protection of their powerful mother, and WK cracked coconuts all the time. When he emigrated as a young man, he found that whenever he cracked a coconut, dominant animals in the new troop took it from him, so he stopped. 436 continued to crack coconuts, but only on rare occasions, when he was alone.)
Biruté Galdikas describes seeing the orangutan Cara react to rainfall by moving into a tree and breaking off two long leafy branches, which she held over her head as an umbrella. Her son Carl scooted over to take advantage of the shelter. On another occasion, Galdikas benefited by an orangutan’s comprehension of the use of actual umbrellas. She was holding a juvenile orangutan on her lap when it began to rain. The young ape reached behind Galdikas, grabbed her umbrella, and passed it to her. Galdikas opened the umbrella, and several young orangutans joined her under its shelter. At the time, Galdikas was thinking about not getting wet. Only later, viewing a videotape of the incident, did she stop to be impressed by the young ape’s understanding of the tool and its use.
Chantek
Chantek is an orangutan raised until the age of nine by Lyn Miles, who considers him her cross-fostered son. He learned a modified form of sign language, along with other things, such as the route to his favorite hamburger stand. Miles is fond of crafts and passed this along to her orange child. He wove crude potholders on little looms and made laced-up leather purses. As a child, Chantek played with large wooden beads strung on heavy string, a common toy. As Chantek’s fine motor control improved, Miles brought him jewelry-making materials.
Today, when Miles visits Chantek at Zoo Atlanta, where he was transferred by the Yerkes Primate Center, she sometimes brings him jewelry kits in Ziploc plastic bags. Riveting video shows Chantek opening a bag and extracting a stiffened beading thread. He takes the bag of small beads, sticks out his lower lip like a steam shovel, and pours
the beads into his mouth.
Taking the thread in his hand (Chantek is a lefty), he delicately extrudes a single bead from his lips onto the thread, and then another. If a bead displeases him, he sucks it back off the thread and extrudes another. The first time he made a necklace from one of these kits, the result was not what Chantek had in mind. “He didn’t like it so he took it all apart, put it back in the bag, put the cord back in the bag, sealed it up, and gave it back to me,” Miles said.
When he is finished, he has made a respectable beaded necklace that could be offered for sale anywhere.* His neck is so huge that he cannot wear it, although upon request he will put it on top of his head or on his beard, and he gives finished necklaces to Miles or occasionally to his companions. While Chantek works, his cagemates watch, their faces so close that they practically have their eyeballs on his lips.
Chantek became skilled with tools (hammer, pliers, wire-cutter, wrench, etc.) while he lived with Miles, and at the zoo he sometimes steals tools from the janitors, which he will only give back if asked nicely. In sign language. Which the janitors do not speak.†
Another literal tool user was Lucy, a chimpanzee raised in the Temerlin family. She knew how to use a screwdriver after seeing Maurice Temerlin use it once. She used it to dismantle a light fixture, learned from the experience how to dismantle light fixtures without getting shocked, and stole it whenever she could for such projects as taking the kitchen door off its hinges.
Chimpanzees
In 1960, when Jane Goodall was first observing wild chimpanzees at Gombe, Tanzania, the project was in peril. Goodall’s mentor, Louis Leakey, had gotten funding for only six months, and Goodall hoped to make discoveries that would draw more funding. The study was saved when she saw a chimpanzee, David Greybeard, modifying a stick into a tool for termite dipping by pulling off the leaves. “When I was at school we defined humans as ‘man the toolmaker.’ I sent Louis Leakey a telegram—I actually couldn’t believe my eyes—and he sent back a famous telegram: ‘Ha ha now we must redefine man, redefine tool, or accept chimpanzees as human.’”
The next snack sensation
David Greybeard was dipping a stick into a hole in a termite mound so enraged termites would seize the invading stick with their iron jaws, and he could pull them out and eat them. Sounds straightforward, but it takes years to become proficient. Here’s what a chimpanzee child must learn to become a competent termite dipper. (We know because researchers tried it themselves.) First find a termite mound (and this is where I always fail), figure out where the tunnels are, and scratch a hole into one of them. Select a stick of the right elasticity, one that will bend with the bends in the tunnels but will not break. Remove leaves and projecting twigs and perhaps bite it to the right length. Then thread the stick into the passageway and wiggle it so that termites will detect it and grab on. Lastly, pull the stick out without knocking all the termites off.
Infant chimpanzees don’t even try to fish for termites. They sit nearby while their mother fishes, watching her, playing with sticks, and occasionally eating a termite. Two-year-olds jab things in the termite mound randomly. Their sticks are the wrong size and the wrong kind. They insert sticks too clumsily and pull them out too soon. Three-year-olds do a little better, using longer sticks and showing more patience. Four-year-olds do better still, and they do catch termites, although they don’t keep it up as long as grown-ups do. By five or six they do it as well as adults.
Ants
The chimpanzee children of Gombe take longer to master dipping for ants than dipping for termites because the ants bite. If an infant isn’t clinging to its mother while she dips for ants it stays a safe distance away. Jane Goodall has described the chimpanzee Winkle dipping for safari ants while her four-year-old child Wonder sat apart with her own dipping stick, in the same pose as her mother, busily dipping for nothing at all.
So a five-or six-year-old ape that’s skilled at termiting will still be a klutz at anting, will use poorly designed tools and wield them ineptly. At Gombe the accepted way to dip for ants is to select a fairly rigid stick, insert it into the ant hole, and stir. The ants will rush up the stick, plotting against you. When they are three-quarters of the way up, pull the stick out—act fast—and pull it through your other hand, crumpling the ants into a ball. Slap your hand to your mouth and chew quickly, before they bite you.
This seems to be a more efficient scheme, in terms of ants per minute, than the one used by the chimpanzees in the Taï Forest preserve in the Ivory Coast. There they simply put a stick in the ant hole, get a few ants on it, and nip them off the stick. They get a quarter as many ants. The chimpanzees at Gombe and Taï are eating the same species of ant, and primatologist Christophe Boesch has personally tried both techniques at Taï and found that both work.
Ants climbing up tree
The chimpanzees of Mahale, not far from Gombe, fish for wood-boring ants, usually in trees. Often a chimpanzee makes a tool and then travels to the tree, carrying the tool in its mouth or armpit or tucked between neck and shoulder or between thigh and abdomen. To get at the ants’ nest, the chimpanzees may have to assume awkward and innovative positions.
Again, it takes time to learn this skill. As reported by anthropologists Toshisada Nishida and Mariko Hiraiwa, the two-year-old MA tried to get ants without a stick, got bitten on the foot, and hopped in agony. He also hung by his hands and tried to stick his finger in the entrance. Another young chimpanzee, Katabi, used a tool for the first time when he was almost three, spending six minutes preparing a branch tool. But it was too short and when he stuck it in the entrance hole it nearly vanished. When he was four, he climbed on the shoulder of an adult, Kamemanfu, who was ant fishing, and tried to fish from there, but Kamemanfu barked at him and Katabi’s mother had to come get him. When he was nearly five he fished steadily for 23 minutes with a bark tool, until Kamemanfu chased him away. When he was over six, researchers still considered his technique clumsy and his persistence inadequate. He got bitten a lot.
Nuts
Chimpanzees in many areas crack nuts, and these can be a significant part of their diet. At Bossou, Guinea, their main foods are fruit, but during the middle part of the rainy season there’s not much fruit, and they fall back on oil palm nuts, the pith of oil palms, and the fruit of the umbrella tree. Since tools are required to eat both the pith and the nuts of oil palms, primatologist Gen Yamakoshi argues that this population depends on tools for subsistence.
Researchers at Bossou set up an “outdoor laboratory,” an open place where the presence of oil palm nuts and good stones for cracking nuts, both gathered by researchers, attracted chimpanzees. Observers crouched behind a screen. Researcher Tetsuro Matsuzawa examined the development of nut cracking in young apes. In the first stage, the infants hung out while their mothers cracked nuts, and manipulated one object at a time. One-year-olds would pick up a nut or roll it around on the ground or hold it in their mouths. They’d touch or hit or roll a stone. They would eat nut kernels their mothers gave them. Around two years old, the little apes would associate two objects: they’d push a nut against a stone or push a nut with a stone. They might put a nut on a stone. They began to attack the nuts, hitting them with hand or foot.
At three they’d put a nut on an anvil and hit it with their hand. Gradually they’d coordinate and string together their actions to crack nuts. By six or seven they were fully competent. At six and a half, Na used a third stone, a wedge, to level his anvil stone. Young chimpanzees whose mothers did not crack nuts (perhaps because of physical injuries) still learned to do it themselves.
Palm hearts, algae, and honey
At Bossou the chimpanzees have a clever and perhaps unique foraging activity—pestle pounding. This is a way of getting pith from the center of the stem of an oil palm. To do it you climb up into the top of an oil palm. Perhaps you pull out and eat the tender bases of the center fronds. Then you take a petiole of another frond and use it as a pestle to pound on and then excavate the soft j
uicy pulp in the crown of the palm. Also at Bossou, chimpanzees use sticks to skim algae from ponds. Chimpanzees in the Lossi Forest, Congo, use sticks to get honey.
Climbing shoes
Chimpanzees in Tenkere, Sierra Leone, like to eat the fruits and flowers of kapok trees. The kapok trees, as if foreseeing this eventuality, are studded with large sharp thorns. Apes move slowly and carefully through the branches. In Tenkere, but not in other places where chimpanzees feed in kapok trees, some of them use sticks to protect their feet and to sit on while they feed in these trees. Researcher Rosalind Alp first saw this in a teenager who twisted off a small thornless branch, put it in front of him on a thorny branch, and stepped on it, gripping it between his great and lesser toes. Standing on it, he picked fruit. The next day Alp saw a teenager (perhaps the same one) make “stepping sticks” for each foot. Sometimes when he wanted to move he moved the stick with his hand and stepped on it; other times he gripped it with his toes and moved his foot, carrying the stick with it like a sandal. Adults also stood and sat on sticks in kapok trees.
Like a Rock
An enclosure was designed for the purpose of holding and viewing a colony of captive chimpanzees. A paddock was built around an area with shade trees. Planks were fixed between the trees to form passages and climbing places for the apes. Above the planks, electrified wiring was wrapped around the tree trunks, because in a confined area animals often overuse and destroy plants. The 18-foot-high fence was chain-link topped with two sections of sheet metal, the top section of which leaned in at a 30-degree angle. An observation booth with large windows was built atop the fence. It was very nice, and carefully thought out, and then they added chimpanzees.
Becoming a Tiger: The Education of an Animal Child Page 27