I first encountered the tube task during a visit to Jigokudani Monkey Park, in Japan, in one of the world’s coldest habitats with native primates. Tourist guides use the task to demonstrate monkey intelligence. At the feeding site next to the river, which attracts snow monkeys from the surrounding montane forest, a horizontal transparent tube was baited with a piece of sweet potato. Rather than wielding a stick like the capuchins, one female snow monkey pushed her small infant into the tube while firmly holding on to its tail. The baby crawled toward the food and grabbed it, only to be quickly withdrawn by its loving mom, who pried the prize from its resistant clutch. Another female collected rocks to throw into one end of the tube, so that the food came out the other end.
These are macaques, monkeys much closer to us than capuchins. The most spectacular evidence for macaque tool use has been collected by Michael Gumert, an American primatologist. On Piak Nam Yai Island off the coast of Thailand, Gumert found an entire population of long-tailed macaques using stone tools. I am very familiar with this species, having done my dissertation on them. Also known as crab-eating macaques, these smart monkeys are rumored to hang their long tails in water to pull up crabs. I have seen them use their tail almost like a stick to obtain food. Unable to control it as South American primates do—a macaque’s tail is nonprehensile—they grab their tail with one hand and swap food from outside to inside their cage with it.
Manipulating one’s own body appendage is yet another example that stretches the definition of tool use, but there is no doubt that what Gumert discovered is a well-developed technology. His monkeys on the coast collect stones everyday for two purposes. Bigger stones serve as hammers to pound oysters with blunt force until they break open, revealing a delicious rich food source. Smaller stones are used rather like axes, applying a precision grip and more rapid movements, in order to dislodge shellfish from rocks. During the few hours of ebb tide, both food and tools are abundant, an ideal situation for the invention of this seafood technology. It is testimony to the generalized intelligence of primates, because obviously they evolved in the trees, eating fruits and leaves, but here they were surviving on the beach. After humans, chimps, and capuchins, a fourth primate has entered the Stone Age.35
Beyond the primates, however, there are quite a few tool-using mammals and birds. Coastal Californians can watch their own floating technology every day among the kelp. The popular furry sea otter swims on his back while using both front paws to smash shellfish against a stone anvil on his chest. He also hammers abalones with a large rock to dislodge them, taking multiple dives to finish this underwater job. A close relative of the otter may possess even more spectacular talents. The honey badger is the star of a viral YouTube video full of expletives to indicate how “badass” this Chuck Norris of the animal kingdom is. The species is even featured on T-shirts emblazoned with “Honey badger don’t care.” This so-called badger is a small carnivore, which actually—like the otter—belongs to the weasel family. While I know of no official reports about their skills, a recent PBS documentary features a rescued honey badger named Stoffel who invents multiple ways to escape from his enclosure at a South African rehabilitation center.36 Assuming that what we see is not a trained trick, he outwits his human caretakers at every turn and displays the sort of insight for his Houdini act that one might expect from an ape, not a honey badger. The documentary shows Stoffel leaning a rake against the wall and claims that he once piled up large stones against it to escape. After all the stones were removed from his enclosure, he apparently constructed a heap of mud balls for the same purpose.
Even though all this is most impressive and begs for further investigation, the greatest challenge to the supremacy of primates has come, not from other mammals, but from a flock of squawking and cawing birds that landed right in the midst of the tool debate. They caused about as much mayhem as they did in that Hitchcock movie.
During the quiet hours in his pet store, my grandfather patiently trained goldfinches to pull a string. This particular finch is known in Dutch as a puttertje, a name that refers to the drawing of water from a well. Males that could both sing and draw would fetch a high price. For centuries, these little colorful birds were kept in homes with a chain around their leg, pulling a thimble up from a glass so as to fetch their own drinking water. One such finch is featured in the seventeenth-century Dutch painting central to Donna Tartt’s novel The Goldfinch. Of course, we don’t keep these birds anymore, at least not in this cruel fashion, but their traditional trick is very similar to the one that, in 2002, gave us Betty the crow.
In an aviary at Oxford University, Betty was trying to pull a little bucket out of a transparent vertical pipe. In the bucket was a small piece of meat, and next to the pipe were two tools for her to choose from. One was a straight wire, the other a hooked one. Only with the latter could Betty get a hold of the bucket’s handle. After her companion stole the hooked wire, however, she faced the task with an inappropriate tool. Undeterred, Betty used her beak to bend the straight wire into a hook so as to pull the bucket from the tube. This remarkable feat was a mere anecdote until perceptive scientists systematically investigated it with new tools. In subsequent tests, Betty received only straight wires, which she kept subjecting to her remarkable bending act.37 Apart from dispelling the “birdbrain” notion with which birds are unfairly saddled, Betty achieved instant fame by giving us the first laboratory proof of toolmaking outside the primate order. I add “laboratory,” because Betty’s species in the wild, in the Southwest Pacific, was already known for tool crafting. New Caledonian crows spontaneously modify branches until they have a little wooden hook to fish grubs out of crevices.38
Inspired by an Aesop fable, crows have been tested to see if they will throw stones into a tube filled with water to bring floating rewards within reach. They do.
The Ancient Greek poet Aesop may have had an inkling of these talents given his fable The Crow and the Pitcher. “A Crow, half-dead with thirst,” so the fabulist went, “came upon a Pitcher.” There wasn’t enough water in the pitcher for the crow to be able to drink it. He tried to reach in with his beak, but the water level was too low. “Then a thought came to him,” as Aesop put it, “and he took a pebble and dropped it into the Pitcher.” Many more pebbles followed until the water had risen enough for a drink. It seems an unlikely feat, but it has now been replicated in the lab. The first was an experiment on rooks, a corvid that in the wild does not use any tools. The rooks were presented with a vertical water-filled tube with a floating mealworm just out of reach. The water level would have to be raised if the rook were to reach the delicacy. The same experiment was carried out with New Caledonian crows, known as real tool experts. True to the dictum that necessity is the mother of invention, and confirming Aesop’s story several millennia later, both crow species successfully solved the floating worm puzzle by using pebbles to raise the water level in the tube.39