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Extensive toolkits give chimps a taste of honey

Central African apes use sets of as many as five modified sticks to extract snacks from hives

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2:30pm, May 28, 2009
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Chimpanzees living in central Africa’s dense forests have no access to a hardware store, but that doesn’t stop them from assembling their own brand of toolkits. These apes use as many as five homemade tools in set sequences to obtain honey from beehives located at least 20 meters high in the trees, in fallen tree trunks and up to 1 meter underground, according to two new studies.

Chimps living in Gabon’s Loango National Park modify tree branches of various lengths and widths to make complex tool sets for removing honey from the hives of different bee species, anthropologist Christophe Boesch of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and his colleagues report online May 19 in the Journal of Human Evolution. In other parts of Africa, chimps use only one or two tools at a time to obtain honey from hives, crack nuts or hunt small animals.

Near Loango, in a forested region of the Congo Basin called the Goualougo Triangle, another group of chimps also makes and uses different types of tools to open beehives and gather honey, say Crickette Sanz, also of the Max Planck Institute for Evolutionary Anthropology, and David Morgan of Lincoln Park Zoo in Chicago.

Chimps across Africa have developed regional tool-using traditions in honey gathering, Sanz and Morgan propose in the June International Journal of Primatology. In central African forests, hard-to-reach hives and competition for food with nearby gorillas have elicited complex forms of tool use by chimps, the researchers contend. That proposal challenges the traditional idea that advanced behaviors among human ancestors emerged only after they left the forest for wide-open savannas. Forest-dwelling ancestors could have achieved chimplike advances in tool-making as well, in Sanz and Morgan’s view.

The findings further narrow the proposed divide between human and chimp tool use, Boesch asserts. “Specific nest structures affect honey-extraction techniques used by chimpanzees, and the animals are surprising us with the solutions they can come up with,” he says.

Anthropologist Craig Stanford of the University of Southern California in Los Angeles agrees. “Using up to five tools in sequence is startlingly complex, even compared to the degree of technological savvy we know chimpanzees possess,” Stanford comments.

From February 2005 through September 2007, Boesch’s team collected more than 100 honey-gathering tools used by the Loango chimps. Many implements lay in piles at the base of trees or near entrances to underground nests. Boesch’s team also observed more than a dozen instances of chimps, in groups of two to 12, using several tools to extract honey from hives in trees and in fallen branches. In some cases, chimps modified both ends of a stick so that it could be used for two purposes.

Five different tools with distinctive signs of wear on their ends were identified: Pounders are thick sticks with rounded ends that chimps hammer against hives to create an opening. Enlargers are thinner sticks used to break apart compartments within hives. Chimps then dip or scoop honey out of hives using branches with frayed ends that the researchers refer to as collectors. Strips of bark, or swabbers, are also used to spoon honey out of opened hives.

And, though no sightings were made of chimps gathering honey from underground hives, sticks left by those hives suggest an additional tool is used to probe the soil. Long sticks, called perforators, are thrust into the soil to locate chambers before any of the other tools are employed, Boesch suggests. Then the apes dig a narrow, angled tunnel that enables them to reach a buried chamber without letting soil mix with removed honey.

Boesch hopes that video cameras set up in the forest will record chimps gathering honey from underground hives.

Between 2002 and 2006, Sanz and Morgan observed 40 instances of Goualougo chimps using sets of two to five tools to gather honey, mainly from tree hives but also from fallen trees and underground hives. Tool behavior was consistent with Boesch’s descriptions of how Loango chimps employed their implements. Goualougo chimps also make toolkits, not just individual tools (SN:10/23/04, p. 269), for extracting termites from their nests, the researchers say.

Goualougo chimps succeeded in extracting honey from beehives on only half of their observed attempts. Successful hive raids yielded anywhere from a few drops of honey to several handfuls of honeycomb, suggesting that chimps often got a modest nutritional return for their efforts, Sanz and Morgan suggest.

In Loango, chimps frequently took large amounts of honey from hives, Boesch notes.

No evidence of tool use among ancient members of the human evolutionary family, or hominids, exists before 2.5 million years ago. But the new findings suggest that hominids, such as more than 3-million-year-old species that included Lucy, also could have made wooden tools for gathering honey, Boesch says.

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