We humans rely on a suite of cues to recognize our friends, such as their smiles, their voices, or the way they walk. Biologists have known for several decades that dolphins form close friendships, and that the cetaceans identify pals by their unique whistles. Now new surprising research suggests bottlenose dolphins use their sense of taste to discern their friends’ urine from unrelated dolphins. 

Study leader Jason Bruck, a marine biologist at Stephen F. Austin State University in Texas, didn’t set out to test whether bottlenose dolphins could identify each other through their urine. His original goal was to test whether dolphins use their signature whistles in the same way people rely on names. But