When Jaws swims in for the kill, it's to the foreboding music of John Williams. But piranhas sound their own drumbeats. Red-bellied piranhas (Pygocentrus nattereri), for example, make barking noises when caught. To figure out how the fish vocalize underwater, researchers observed them in a tank. The fierce predators made three types of angry grunts: First, when fish stare down their rivals face-to-face, they utter rapid calls, much like those same barks. During full fish-on-fish fights, the piranhas tend to emit two low thuds. The scrappy fish achieved both noises using ultra-fast muscles that beat against their swim bladders, air-filled chambers that aid in flotation, the group reports today in The Journal of Experimental Biology. The third call is the nastiest; piranhas gnash their teeth while chasing another fish away from their dinner.
See more ScienceShots.