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For First Time, Chimps Seen Making Weapons for Hunting

Bo is one of the chimps on the Senegal being studied by researchers, who recently discovered that chimps have the ability to make their own weapons to hunt small mammels.
Bo is one of the chimps on the Senegal being studied by researchers, who recently discovered that chimps have the ability to make their own weapons to hunt small mammels. (Paco Bertolani)

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In a typical sequence, the animal first discovered a deep tree hollow suitable for bush babies, which are nocturnal and weigh about half a pound. Then the chimp would break off a branch -- on average about two feet long, but up to twice that length -- trim it, sharpen it with its teeth, and poke it repeatedly into the hollow at a rate of about one or two jabs per second.

After every few jabs, the chimpanzee would sniff or lick the branch's tip, as though testing to see if it had caught anything.

In only one of the 22 observations did a chimp get a bush baby. But that is reasonably efficient, Pruetz said, compared with standard chimpanzee hunting, which involves chasing a monkey or other prey, grabbing it by the tail and slamming its head against the ground.

In the successful bush-baby case, the chimpanzee, after using its sharpened stick, jumped on the hollow branch in the tree until it broke, exposing the limp bush baby, which the chimp then extracted. Whether the animal was dead or alive at that point was unclear, but it did not move or make any sound.

Chimpanzees are believed to offer a window on early human behavior, and many researchers have hoped that the animals -- humans' closest genetic cousins -- might reveal something about the earliest use of wooden tools.

Many suspect that the use of wooden tools far predates the use of stone tools -- remnants of which have been found dating from 2 1/2 million years ago. But because wood does not preserve well, the most ancient wooden spears ever found are only about 400,000 years old, leaving open the question of when such tools first came into use.

The discovery that some chimps today make wooden weapons supports the idea that early humans did too -- perhaps as much as 5 million years ago -- Stanford said.

Adrienne Zihlman, an anthropologist at the University of California at Santa Cruz, said the work supports other evidence that female chimps are more likely than males to use tools, are more proficient at it and are crucial to passing that cultural knowledge to others.

"Females are the teachers," Zihlman said, noting that juvenile chimps in Senegal were repeatedly seen watching their mothers make and hunt with spears.

Females "are efficient and innovative, they are problem solvers, they are curious," Zihlman said. And that makes sense, she added.

"They are pregnant or lactating or carrying a kid for most of their life," she said. "And they're supposed to be running around in the trees chasing prey?"

Frans B.M. de Waal, a primatologist at Emory University, said aggressive tool use is only the latest "uniquely human" behavior to be found to be less than unique.

"Such claims are getting old," he said. "With the present pace of discovery, they last a few decades at most."


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