Are We Smart Enough to Know How Smart Animals Are? (12 page)

Apes do not just search for tools for specific occasions; they actually fabricate them. When the British anthropologist Kenneth Oakley, in 1957, wrote
Man the Toolmaker
, which claimed that only humans make tools, he was well aware of Köhler’s observations of Sultan fitting sticks together. But Oakley refused to count this as tool manufacture, since it was done in reaction to a given situation rather than in anticipation of an imagined future. Even today some scholars dismiss ape tools by stressing how human technology is embedded in social roles, symbols, production, and education. A chimpanzee cracking nuts with rocks doesn’t qualify; nor, I suspect, does a farmer picking his teeth with a twig. One philosopher even felt that since chimpanzees don’t
need
their so-called tools, it remains a feeble comparison.
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One of the most complex tool skills is the cracking of tough nuts with rocks. A wild female chimpanzee selects an anvil stone and finds a hammer that fits her hand to open a nut, while her son watches and learns. Only by the age of six will he reach adult proficiency.

I feel like recalling my know-thy-animal rule here, according to which we can safely dismiss a philosopher who thinks that wild chimpanzees sit there pounding and pounding hard nuts with rocks, an average of thirty-three blows per consumed kernel, for generation after generation, for no good reason at all. During peak season, chimpanzees at some field sites spend close to 20 percent of their waking hours fishing with twigs for termites or cracking nuts between rocks. It is estimated that they gain nine times as many kilocalories of energy from this activity as they put into it.
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Moreover, the Japanese primatologist Gen Yamakoshi found that nuts serve as fallback foods when the apes’ main nutrition—seasonal fruits—is scarce.
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Another fallback is palm pith, which is obtained through “pestle pounding.” High up in a tree, a chimpanzee stands bipedally at the edge of the tree crown, pounding the top with a leaf stalk, thus creating a deep hole from which fiber and sap can be collected. In other words, the survival of chimpanzees is quite dependent on tools.

Ben Beck gave us the best-known definition of tool use, of which the short version goes as follows: “the external deployment of an unattached environmental object to alter more efficiently the form, position, or condition of another object.”
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Though imperfect, this definition has served the field of animal behavior for decades.
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Tool manufacture can then be defined as the active modification of an unattached object to make it more effective in relation to one’s goal. Note that intentionality matters a great deal. Tools are brought in from a distance and modified with a goal in mind, which is the reason traditional learning scenarios, which revolve around accidentally discovered benefits, have such trouble explaining this behavior. If you see a chimpanzee strip the side branches off a twig to make it right for ant fishing, or collect a fistful of fresh leaves and chew them into a spongelike clump to absorb water from a tree hole, it is hard to miss the purposefulness. By making suitable tools out of raw materials, chimpanzees are exhibiting the very behavior that once defined
Homo faber
, man the creator. This is why the British paleontologist Louis Leakey, when he first heard about such behavior from Goodall, wrote her back, “I feel that scientists holding to this definition are faced with three choices: They must accept chimpanzees as man, they must redefine man, or they must redefine tools.”
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After the many observations of chimpanzee tool use in captivity, seeing tool use in the wild by the same species did perhaps not come as a surprise, yet its discovery was crucial since it could not be explained away by human influence. Moreover, wild chimps not only use and make tools, but they learn from one another, which allows them to refine their tools over generations. The result is more sophisticated than anything we know in zoo chimps. A good example are the
toolkits
, which can be so complex that it is hard to imagine that they were invented in a single step. A typical one was found by the American primatologist Crickette Sanz in the Goualougo Triangle, Republic of Congo, where a chimpanzee may arrive with two different sticks at a particular open spot in the forest. It is always the same combination: one is a stout woody sapling of about a meter long, while the other is a flexible slender herb stem. The chimp then proceeds to deliberately drive the first stick into the ground, working it with both hands and feet the way we do with a shovel. Having made a sizable hole to perforate an army ant nest deep under the surface, she pulls out the stick and smells it, then carefully inserts her second tool. The flexible stem captures bite-happy insects that she pulls up and eats, dipping regularly into the nest below. Apes often climb off the ground, moving onto tree buttresses, to avoid the nasty bites of colony defenders. Sanz collected more than one thousand such tools, which shows how common the perforator-dipping combination is.
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More elaborate toolkits are known for chimpanzees in Gabon hunting for honey. In yet another dangerous activity, these chimps raid bee nests using a five-piece toolkit, which includes a pounder (a heavy stick to break open the hive’s entrance), a perforator (a stick to perforate the ground to get to the honey chamber), an enlarger (to enlarge an opening through sideways action), a collector (a stick with a frayed end to dip into honey and slurp it off), and swabs (strips of bark to scoop up honey).
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This tool use is complicated since the tools are prepared and carried to the hive before most of the work begins, and they will need to be kept nearby until the chimp is forced to quit due to aggressive bees. Their use takes foresight and planning of sequential steps, exactly the sort of organization of activities often emphasized for our human ancestors. At one level chimpanzee tool use may seem primitive, as it is based on sticks and stones, but on another level it is extremely advanced.
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Sticks and stones are all they have in the forest, and we should keep in mind that also for the Bushmen the most ubiquitous instrument is the digging stick (a sharpened stick to break open anthills and dig up roots). The tool use of wild chimpanzees by far exceeds what was ever held possible.

Chimpanzees use between fifteen and twenty-five different tools per community, and the precise tools vary with cultural and ecological circumstances. One savanna community, for example, uses pointed sticks to hunt. This came as a shock, since hunting weapons were thought to be another uniquely human advance. The chimpanzees jab their “spears” into a tree cavity to kill a sleeping bush baby, a small primate that serves as a protein source for female apes unable to run down monkeys the way males do.
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It is also well known that chimpanzee communities in West Africa crack nuts with stones, a behavior unheard of in East African communities. Human novices have trouble cracking the same tough nuts, partly because they do not have the same muscle strength as an adult chimpanzee, but also because they lack the required coordination. It takes years of practice to place one of the hardest nuts in the world on a level surface, find a good-sized hammer stone, and hit the nut with the right speed while keeping one’s fingers out of the way.

The Japanese primatologist Tetsuro Matsuzawa tracked the development of this skill at the “factory,” an open space where apes bring their nuts to anvil stones and fill the jungle with a steady rhythm of banging noise. Youngsters hang around the hardworking adults, occasionally pilfering kernels from their mothers. This way they learn the taste of nuts as well as the connection with stones. They make hundreds of futile attempts, hitting the nuts with their hands and feet, or aimlessly pushing nuts and stones around. That they still learn the skill is a great testament to the irrelevance of reinforcement, because none of these activities is ever rewarded until, by about three years of age, the juvenile starts to coordinate to the point that a nut is occasionally cracked. It is only by the age of six or seven that their skill reaches adult level.
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When it comes to tool use, chimps always catch the limelight, but there are three other great apes—bonobos, gorillas, and orangutans—that, together with chimps, us, and the gibbons, make up the Hominoid family. Not to be confused with monkeys, Hominoids are large, flat-chested primates without tails. Within this family, we are closest to chimps and bonobos, both of which are genetically nearly identical to us. Naturally, there is heated debate about what the minuscule-sounding 1.2 percent DNA difference between us and them exactly means, but that we are close family is not in doubt. In captivity, the orangutan is an absolute master tool user, dexterous enough to tie knots into loose shoelaces, and to construct instruments. One young male was seen to join three sticks, which he had first sharpened, into two tubes to build a five-section pole to knock down suspended food.
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Being notorious escape artists, orangs may dismantle their cage so patiently, from day to day and week to week, while keeping dislodged screws and bolts out of sight, that keepers fail to notice what they are doing until it’s too late. In contrast, until recently all we knew about wild orangs was that they sometimes scratched their butt with a stick or held a leafy branch over their head during rain. How could a species that is so talented offer so little evidence of tool use in the wild? The inconsistency was resolved when, in 1999, the tool technology of orangutans in a Sumatran peat swamp came to light. These orangs extract honey from bee nests with twigs and use short sticks to remove the seeds embedded in the stinging hairs of
n
eesia
fruits.
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The other ape species, too, are perfectly capable of tool use, and we have already laid to rest the view that gibbons lack this capacity.
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But reports from the wild remain meager to nonexistent, sometimes suggesting that only chimps are proficient tool users. We see glimpses, such as when gorillas preventively disarm poacher snares, which requires a grasp of basic mechanics, or traverse deep water. When elephants had dug a new water hole in a swampy forest in the Republic of Congo, the German primatologist Thomas Breuer saw a female gorilla, Leah, try to wade across. She stopped when she was waist-deep into it, however—apes hate swimming. Leah returned to shore to pick up a long branch to gauge the water’s depth. Feeling around with her stick, she walked bipedally far into the pool before retracing her steps to return to her wailing infant. This example highlights the shortcomings of Beck’s classical definition, because even though Leah’s stick altered neither anything in the environment nor her own position, it did serve as a tool.
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Chimpanzees are recognized as the most versatile primate tool user apart from us, but this heralded position has been challenged. The challenge did not come from any Hominoid but from a small South American monkey. Brown capuchin monkeys have been known for centuries as organ-grinders and more recently as trained helping hands for quadriplegics. They are extremely manipulative and particularly good at tasks that tap into their tendency to smash and bang things. Having had a colony of these monkeys for decades, I know that almost anything you hand them (a piece of carrot, an onion) is going to be pounded to mush on the floor or against the wall. In the wild, they pound oysters for a long time until the mollusk relaxes its muscle so they can pry it open. During the fall, our monkeys in Atlanta collected so many fallen hickory nuts from nearby trees that we’d hear frantic banging sounds the whole day in our office adjacent to the monkey area. It was a happy sound, because capuchins seem to be in their best mood when they are doing things. Not only did they try to break open the nuts, they also employed hard objects (a plastic toy, a block of wood) to smash them with. About half the members of one group learned to do so, whereas the second group never invented the technique despite having the same nuts and tools. This group obviously consumed fewer nuts.

Capuchins’ natural predisposition to be persistent pounders sets them up for nut cracking in the field. A Spanish naturalist first reported it five centuries ago, and more recently an international team of scientists found dozens of cracking sites in the Tietê Ecological Park and other sites in Brazil.
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At one site, capuchins eat the pulp of a large fruit, after which they drop its seeds to the ground. They return a couple of days later to collect those seeds, which by then have dried out and are often infested with larvae, which the monkeys are fond of. Traveling with the seeds stuffed in their hands, mouth, and (prehensile) tail in search of a hard surface, such as a large rock, the monkeys would get a smaller stone to pound the seeds with. While these stones are about the same size as those used by chimps, the capuchins are only about the size of a small cat, so their hammers weigh about one-third of their body! Literally acting as heavy equipment operators, they lift them high above their heads to get a good hit. When the tough seeds are cracked, the larvae are there for the picking.
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