CULTURAL TRANSMISSION: A new study shows the first evidence that chimpanzees can acquire new traditions and pass them on to other chimps outside of their groups.
IMAGE BY LEWIS HOUGHTON

A new study of chimpanzee populations has shown for the first time that humans' closest relatives teach new customs to fellow chimps in their own as well as neighboring communities.

"Until now, there was no evidence that [nonhuman] primates could spread learned behavior from one group to another," says Antoine Spiteri, a doctoral candidate at the University of St. Andrews in Scotland. Spiteri, who works in the lab of Andrew Whiten, a professor of evolutionary and developmental psychology, is lead author of the study published in Current Biology.

Primatologists—including teams from the University of Texas M.D. Anderson Cancer Center's Science Park in Bastrop, Tex., and the Yerkes National Primate Research Center of Emory University in Atlanta, Ga.—trained eight chimps, each from a different community (consisting of seven to 17 members), to use devices to access fruit inside them. The researchers discovered the chosen chimps eagerly passed along their newly acquired skills to peers within their eight communities when the latter were also exposed to similar contraptions.

In one case, the animals were trained to turn a handle to force the fruit down a shoot and then to slide a gadget to guide it into a hole in the box big enough for them to reach in and remove it. In other instances, they were taught maneuvers such as stabbing, lifting a bar or depositing a coin to access the coveted food. "The more individuals that learn[ed] the task, the more of a tradition it would become," Spiteri says.

When more than 50 percent of a group learned the drill, researchers moved the box to a corner of the habitat in full view of a neighboring chimp community where no member had received training. The curious neighbors watched the skilled chimpanzees, eventually picking up on what the learned group was doing to get to the food; the new foraging techniques were also passed along to a third group confronted with the strange fruit apparatus. In all, the animals adopted and spread 10 new customs during the trials.

These observations show "that chimpanzees can sustain cultures that are made up of several traditions," Whiten says. "This … is consistent with what is seen in the wild where chimpanzees are thought to show up to 20 traditions that define their local culture."

Bennett Galef, an animal behaviorist at McMaster University in Hamilton, Ontario, notes that female chimps in the wild move from group to group and "take learned behavior with them," a practice that supports the new findings.

"Ideally, what I would like to do is look at actual translocations of one chimpanzee from one group to another," Spiteri says, noting, however, that he is "now satisfied that chimpanzees do have the capability to learn from others."