If you want to be lifelong friends with a dolphin, you'd better have their back. New research shows male dolphins will race to assist other dolphins at the sound of their signature whistles—if they're part of the same alliance. The ground-breaking findings suggest dolphins have a concept of team membership that's vocalized, per Science. Male dolphins generally work to find and corral fertile females in fleeting groups of two or three, known as a first-order alliance. But they also have a larger, second-order alliance made up of up to 14 dolphins that work together to defend against rival groups. These groups are much more permanent, staying together for decades or even lifetimes, Stephanie King, a behavioral biologist at the University of Bristol, tells Science. Her research, published in Nature Communications, shows just how committed they are.
Researchers experimented in broadcasting the signature whistles of Indo-Pacific bottlenose dolphins recorded in Western Australia's Shark Bay. These whistles, which researchers liken to a name, are used to "summon one another, and to tell other members of their pod where they are if they lose visual contact," per the New Yorker. It was thought that first-order alliance members would respond most strongly as the whistles played underwater. Instead, in 90% of experiments, it was the second-order alliance members who "turned immediately and directly toward the speaker," says King, who calls the find "striking." This suggests a "social concept of team membership, based on an individual's previous cooperative investment." Even humans' closest living relatives, the chimpanzees, don't use vocal communication to cooperate, instead relying on body language, King tells Science. (Read more dolphins stories.)