In a classic case of "monkey see, monkey do," a group of chimpanzees has been observed keeping up with a somewhat strange fashion trend begun by one female group member.
Researchers say they've amassed 700 hours of video of a troupe of chimpanzees who've decided that sticking a piece of grass in one ear -- a behavior started by just one female chimp dubbed Julie -- is the height of fashion.
After Julie chose the fashion accessory -- for no apparent reason -- the rest of the group quickly jumped on the bandwagon, the researchers report in the journal Animal Cognition.
"This reflects chimpanzees' proclivity to actively investigate and learn from group members' behaviors in order to obtain biologically relevant information," says lead researcher Edwin van Leeuwen, of the Max Planck Institute for Psycholinguistics in The Netherlands, noting that chimps are known to be natural copycats.
Julie, a member of a chimp group living in the Chimfunshi Wildlife Orphanage Trust sanctuary in Zambia, was first observed by van Leeuwen putting a straw-like blade of grass in one or both ears in 2010.
Even while playing, grooming and resting, she was careful to leave the blade of grass in place, van Leeuwen says.
Other chimps began doing the same, and van Leeuwen says he wanted to determine if this was an example of social learning behavior.
In subsequent visits to the sanctuary, studying 94 individual chimps in four different social groups living there, he found just one of the groups -- Julie's -- was regularly practicing the "grass-in-the-ear" fashion style, with as many of eight of the twelve chimps in the group following Julie's lead.
The first to imitate Julie's behavior was Julie's son Jack, then three other chimps that Julie regularly interacted with -- Val, Kathy and Miracle -- picked up the habit.
As a general rule, at least two of the chimps in the group would put grass stems in their ears at the same time, van Leeuwen reported.
Even though Julie has subsequently died, others in the group have kept up the behavior, he says, suggesting animals that find some kind of reward or pleasure in a particular behavior will continue to mimic it even in the originating animals is no longer living.
"The fact that these behaviors can be arbitrary and outlast the originator speaks to the cultural potential of chimpanzees," he says.
