Craig Stanford

Significant Others

When Jane Goodall first watched chimpanzees make simple stick tools to probe into termite mounds, it became clear that tool cultures are not unique to human societies. Of course many animals use tools. Sea otters on the California coast forage for abalones, which they place on their chests and hammer open with stones. Egyptian vultures use stones to break the eggs of ostriches. But these are simple, relatively inflexible lone behaviors. Only among chimpanzees do we see elaborate forms of tools made and used in variable ways, and also see distinct chimp tool cultures across Africa. In Gombe National Park in Tanzania, termite mounds of red earth rise two meters high and shelter millions of the almond-colored insects. Chimpanzees pore over the mounds, scratching at plugged tunnels until they find portals into the mound's interior. They will gently insert a twig or blade of grass into a tunnel until the soldier termites latch onto the tools with their powerful mandibles, then they'll withdraw the probe from the mound. With dozens of soldier and worker termites clinging ferociously to the twig, the chimpanzee draws the stick between her lips and reaps a nutritious bounty.

Less than a hundred kilometers away from Gombe's termite-fishing apes is another culture. Chimpanzees in Mahale National Park live in a forest that is home to most of the same species of termites, but they practically never use sticks to eat them. If Mahale chimpanzees forage for termites at all, they use their fingers to crumble apart soil and pick out their insect snacks. However, Mahale chimpanzees love to eat ants. They climb up the straight-sided trunks of great trees and poke Gombe-like probes into holes to obtain wood-boring species. As adept as Gombe chimpanzees are at fishing for termites, they practically never fish for these ants, even though both the ants and termites occur in both Gombe and Mahale.

Segue two thousand kilometers westward, to a rainforest in Cote d'Ivoire. In a forest filled with twigs, chimpanzees do not use stick tools. Instead, chimpanzees in Tai' National Park and other forests in western Africa use hammers made of rock and wood. Swiss primatologists Christophe and Hedwige Boesch and their colleagues first reported the use of stone tools by chimpanzees twenty years ago. Their subsequent research showed that Tai' chimpanzees collect hammers when certain species of nut-bearing trees are in fruit. These hammers are not modified in any way as the stone tools made by early humans were; they are hefted, however, and appraised for weight and smashing value before being carried back to the nut tree. A nut is carefully positioned in a depression in the tree's above-ground root buttresses (the anvil) and struck with precision by the tool-user. The researchers have seen mothers instructing their children on the art of tool use, by assisting them in placing the nut in the anvil in the proper way.