When Mad, Seahorses Unleash Surprising Sound

What does a seahorse do if you grab it and hold it in place underwater? It growls, of course. It may be a small, low sound, barely audible to the human ear, but scientists in Brazil report in the Journal of Zoology that they used a hydrophone to record audio of seahorses in an aquarium tank as they ate, courted, and were handled by humans, and that the fish definitely growled under duress, reports LiveScience. (Listen to the recordings here.) This is the first time such a sound has been officially detected coming from a seahorse.

“They are cute, monogamous, and calm fish, and people usually love them,” co-author Antonio Souto tells Discovery News. When they are eating, their noises resemble quick clicks, almost like the sound a woodpecker makes against trees. When grabbed and held in place in the tank, though—much like their predators grab and hold them before swallowing them—the seahorses vibrate and growl, possibly as an escape mechanism, the scientists surmise. (Still curious about seahorses? Check out why they're so curvy.)