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Nut-Cracking Ape May Boost Gorillas' IQ Rep

James Owen
for National Geographic News
October 25, 2005
 
Compared to other great apes—chimpanzees, bonobos, and
orangutans—gorillas don't have a reputation for being the sharpest
tools in the box.

But a young female gorilla that uses rocks to smash open nuts may help change that perception, say ape experts, who add that the find may also help shed light on the origins of complex tool use in humans.

Itebero, a two-and-a-half-year-old gorilla from Central Africa, was observed cracking palm nuts between two rocks.

It's the first report of complex tool-use in a gorilla, said Patrick Mehlman, a primatologist with the Dian Fossey Gorilla Fund.

Confiscated from poachers, Itebero has been at the conservation group's gorilla sanctuary in Goma, in the eastern region of the Democractic Republic of the Congo.

Recently she began using a hammer-and-anvil technique to extract oil from palm nuts.

Mehlman says the lowland gorilla started cracking nuts spontaneously and wasn't influenced by humans. "We are unaware that any of her caretakers demonstrated this [behavior] to her," Mehlman noted.

Until recently experts thought that such premeditated use of stones and other tools among nonhuman primates was confined to chimpanzees and bonobos.

Higher Understanding

Gottfried Hohmann, of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, says the finding indicates that gorillas have a higher level of understanding of their environment than previously thought.

Mehlman, the Dian Fossey Gorilla Fund primatologist, says the behavior also suggests that complex tool-use may not have originated in chimps and humans but may have evolved earlier in the primate family tree.

"What this suggests, along with relatively recent findings that some orangutans also use tools in the wild, is that tool use is not just a derived trait for chimpanzees and humans but is present in various degrees for all [living] great apes today, and may have been present in some form in our ape common ancestor," he said.

"It may push back, evolutionarily, the appearance of tool use in ape stocks," Mehlman added.

Support for this idea comes from photographs published last month that show gorillas using sticks and branches to navigate areas of swampy forest. That discovery marked the first time tool use had been documented in wild gorillas.

Thomas Breuer, a biologist with the New York-based Wildlife Conservation Society, took the walking-stick images in the Congo rain forest. The pictures show a female gorilla grabbing a branch to gauge the depth of a pool of water before wading across it.

Another female was also seen using part of a bush as a support while digging for food and as a platform to help her cross a patch of muddy ground.

But more complex tool use, such as that shown by Itebero, does not occur in the wild, according to Craig Stanford, an anthropology professor at the University of Southern California in Los Angeles.

Mountain Gorillas

Stanford has studied both mountain gorillas and chimpanzees in Bwindi-Impenetrable National Park in southwestern Uganda—the only forest in Africa inhabited by both chimps and gorillas.

The anthropologist says he has never observed any gorilla using tools.

Asked to contrast the intellects and problem-solving skills of chimps and gorillas, he said, "No comparison—chimps win hands-down."

Wild chimpanzees and bonobos can be skilled at selecting tools for particular jobs. For instance, they chose modified sticks for extracting termites from termite mounds, rocks for smashing nuts, and leaves for sopping up drinking water.

But Mehlman says it's wrong to see gorillas as simpletons compared to other great apes.

The primatologist notes that chimpanzees in wild populations take a year or more to learn stone nut-cracking from other group members.

Yet "we have a two-and-a-half-year-old gorilla, albeit in captivity, discovering the process for herself and doing it quite competently."

"Gorillas may be quiet and thoughtful. But [they're] clearly not simpleminded," he added. "Also bear in mind that [lowland] gorillas in wild settings have not been observed nearly as often and frequently as chimpanzees."

Mehlman says future research may uncover many other examples of tool use by wild gorillas.

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