Julie acted as a role model for the other 11 chimpanzees in her group. As van Leeuwen points out, "everybody can wear rings in their ears, but you just have to come to the idea to do it." The seven chimps who adopted the grass-in-ear tradition -- and who would continue it after Julie's death -- repeatedly inspected her behavior before trying it themselves.
"The chimps would pick a piece of grass, sometimes fiddle around with it as to make the piece more to their liking, and not until then try and stick it in their ear with one hand," van Leeuwen says. "Most of the time, the chimps let the grass hanging out of their ear during subsequent behavior like grooming and playing, sometimes for quite prolonged times. As you can imagine, this looks pretty funny."