A wild dolphin in south Australia has been teaching members of her group to walk on their tails, a behavior usually seen only after training in captivity. Scientists are scratching their heads -- why would the dolphins do this? Well, one of the female dolphins, Billie, could have learned the behavior by observation during her brief stint in a dolphinarium. Or they might be watching too much Olympic gymnastics. Plus, it just looks like fun. Whatever the reason, it seems to indicate what in humans we call cultural behavior. "These are things that groups develop and are passed between individuals and that come to define those groups, such as language or dancing," one scientist said. So tail walking is to dolphins as, oh, the Soulja Boy dance is to humans...?