食人鱼的沟通方式

Like a pit bull, piranhas will tear the flesh from your bones. Also like a pit bull, they bark. [Piranha audio type 1] Kind of.

Scientists had known that piranha barked when you pick them up – carefully, of course. But they hadn’t known what these sounds were for. So researchers examined how the vocalizations might correspond with behavior.

They dropped a microphone into a piranha tank that, at different times, held three groups of 10 fish. They then placed a mussel in to see how the fish competed for food.

When the fish faced off, they produced that percussive bark. [Piranha audio type 1]

When they circled one another, they made a softer thud sound. [Piranha audio type 2]

A teeth gnashing [Piranha audio type 3] indicated that a piranha was getting pretty ticked off as it chased a competitor.

The first two sounds are produced by muscles contracting around the fish’s swim bladder. The findings are in the Journal of Experimental Biology. [Sandie Millot, Pierre Vandewalle and Eric Parmentier, Sound production in red-bellied piranhas (Pygocentrus nattereri, Kner): an acoustical, behavioural and morphofunctional study. Piranha audio courtesy of Sandie Millot]

The researchers are now interested in whether piranhas vocalize during mating. But they’ll have to travel to Brazil to study this in the wild – turns out that when it comes to mating in captivity, piranhas say no tanks.

—Cynthia Graber