Over at the Telegraph (via news@nature):
A new study shows that male dolphins carry pieces of plants and twigs to impress females, rather than simply playful behaviour as previously believed.
Object-carrying as part of sexual display is rare in the animal kingdom, with only humans and chimpanzees doing anything similar.
The fact that the habit has been observed in isolated populations of dolphins in river dolphins in Brazil, Venezuela and Bolivia suggests it has either been passed on through generations or evolved separately in different groups.
The discovery could provide proof of the existence of dolphin culture – defined as a non-hereditary, complex skill taught to some members of a population by others and passed down through generations.
Culture was until recently seen as a defining human characteristic not shared by other species.