The bottlenose dolphins of John's Pass in Boca Ciega Bay, St. Petersburg FL, exhibit a rare form of self-decoration and social object use called grass-wearing. Self-decoration by wearing grass appears to be an attention-getting device rather than purely play and varies from a single blade to large clusters of grass. John's Pass dolphins self-decorate with grass primarily when they form new social groups or engage in procreative activities. Grass-wearing behavior among these dolphins is a local behavioral tradition that could constitute a cultural difference from other communities.