Like members of a street gang, male dolphins summon their buddies when it comes time to raid and pillage — or, in their case, to capture and defend females in heat. A new study reveals they do this by learning the “names,” or signature whistles, of their closest allies — sometimes more than a dozen animals — and remembering who consistently cooperated with them in the past. The findings indicate dolphins have a concept of team membership — previously seen only in humans — and may help reveal how they maintain such intricate and tight-knit societies.