Piranhas Bark—Three Fierce Vocalizations Deciphered

Piranhas, it turns out, can be excellent communicators, a new study suggests. But don't get the idea they're going soft—their barks, croaks, and clicks likely mean "leave me alone," "I might bite you," or "now I'm really angry!" Researchers knew picking up red-bellied piranhas—among the few piranhas dangerous to humans—could prompt croaks from the fish. Even so, no one had studied their sounds in water or provided good evidence for the barks' evolutionary role. (more)