Hidden cameras in the Congo rainforest have captured the closest look yet at tool use by chimps in the wild, finding that the wily primates use different types of sticks depending on the termite colony they're trying to pillage.
While scientists know chimps use sticks to "fish" for termites, the knowledge is based only on indirect evidence and fleeting field observations. Now David Morgan of the Wildlife Conservation Society and Crickette Sanz, a postdoc at the Max Planck Institute for Evolutionary Anthropology in Leipzig, have obtained an abundance of direct evidence after planting motion-sensing video cameras near termite mounds and nests in a remote area of the Congo Basin called the Goualougo Triangle, which is home to thousands of chimps that have never had any dealings with humans. Over 6 months they filmed 121 chimps that repeatedly visited six termite nests.
In a report published in the November issue of the American Naturalist, the authors describe what they say are "some of the most complex tool kits and techniques that have been observed in wild chimpanzees." The chimpanzees regularly visit two kinds of termite nests and use two different sets of tools to extract their prey. For mounds, the chimps first punch into the nest with a small, short stick. Then they switch to a "fishing probe" that the termites crawl onto. For underground nests, the chimps use a longer "puncturing stick" to get to the nest and follow up with their probes. The videos show them nimbly switching back and forth between the two tools. They can also be seen placing a foot on the stick to push it into the ground like a shovel. In one video, a female chimp pulls a stick through her teeth, shredding the end to make it like a brush, which picks up more termites.
The study fills in a big gap in our knowledge about chimp tool use, says Harvard primatologist Richard Wrangham. "Until now our view of chimpanzee termite-fishing has been overly biased by data on the fringe populations in East Africa." But those chimps only use their hands to puncture termite nests. Wrangham says some scientists have considered tool-use a special adaptation for drier habitats. But this research, which shows it's widespread in equatorial forests, "heralds a new wave of information about the ecological and cultural significance of termite-fishing."