Fashion Trends Even Among Chimps

Like humans, apparently chimpanzees believe in fashion trends, and the latest one that has taken hold among certain groups is what researchers behind a new study are calling "grass-in-the-ear" behavior.

Chimpanzees have a tendency to learn from one another, and in this case they illustrate a perfect example of the old adage "monkey see, monkey do."

As described in the journal Animal Cognition, over 700 hours of video footage showed that when one female chimp named Julie decided to stick a piece of grass in her ear for no apparent reason, it sparked a new trend.

"This reflects chimpanzees' proclivity to actively investigate and learn from group members' behaviors in order to obtain biologically relevant information," lead researcher Edwin van Leeuwen, of the Max Planck Institute for Psycholinguistics in The Netherlands, said in a statement.

In 2010, van Leeuwen first noticed Julie repeatedly put a stiff, straw-like blade of grass in one or both of her ears. She left it there even when she was grooming, playing or resting in Zambia's Chimfunshi Wildlife Orphanage Trust sanctuary. Subsequent visits showed that other chimps had started doing the same.

This ignited van Leeuwen's interest in finding out whether in fact this behavior was an example of social learning. The year-long study looked at 94 chimpanzees living in four different social groups in the sanctuary. The findings showed that one of the four groups regularly performed this so-called "grass-in-the-ear" style. Eight of the twelve chimpanzees in Julie's group repeatedly did so, while only one chimp from another group adopted the behavior as well. The fashion statement took off when Julie's son Jack first copied her, and then other monkeys with whom she regularly interacted also followed suit. Even when Julie died, the others kept it up.

"The fact that these behaviors can be arbitrary and outlast the originator speaks to the cultural potential of chimpanzees," van Leeuwen concluded.