Chimps seemed to have been inspired by one chimpanzee that put a long piece of grass in her ear for looks, because they soon began to follow. This example of social learning in animals in the wild was reported in the journal Animal Cognition. The lead author of the report was Edwin van Leeuwen, a primate expert who is with the Max Planck Institute in The Netherlands.
A chimp named Julie created the new look that became a fad. In 2010, she was observed putting a long piece of grass in her ear and then she began walking around with it hanging from her ear. She did this repeatedly. Then other chimpanzees in her group began to do the same thing. Van Leeuwen noted that the team’s findings are one-of-a-kind in the sense that Julie’s grass usage did not appear to communicate anything. This “grass-in-ear” behavior was called non-adaptive because there seems to have been no communication or other consequences related to having a long piece of grass hanging from one ear.
The grass-in-ear behavior was observed in one group of chimpanzees for one year by the research scientists. Eight of 12 individuals in this group started to put grass in their ears in a similar way to how Julie was “wearing” the grass. As a sort of control, three other groups of chimpanzees in the general area were observed for this behavior as well. In the other three groups, which totaled 82 individuals, there was only one observation of a chimp putting grass in their ear. The authors said that since the social learning behavior was only observed in one group, there could not be an ecological explanation for it. For an unknown reason, Julie must have seemed interesting with grass in her ear and the other chimps in her group paid attention and figured out how to mimic her look.
A key factor in this report is that the observation was made in a natural setting and not in a laboratory setting. This would rule out the intervention of human behaviors in the lab playing a role in getting Julie to put the long piece of grass in her ear for looks, and for other chimps to follow. It might be interesting, however, to create a laboratory experiment designed to get chimps to put grass in their ears. Perhaps scientists could discover a lot about social learning if they tried to encourage this fad in the lab. One possibility is for an experiment to start with humans putting grass in a chimp’s ear, or for an experiment to start with a human walking around with a piece of grass in their ear for other humans to pick up the behavior. Graduate students have been asked to do many things but maybe this would be going too far.
Social learning in animals is a growing interest in the study of animal behavior. Over the last few decades, scientists have shown that animal behavior, cognition and language abilities are much more advanced than previously thought. Chimps following other chimps by putting a long piece of grass in the ear for looks is a very interesting case of social learning and is sure to be studied more in the future.
By Margaret Lutze