Piranhas Bark—Three Fierce Vocalizations Deciphered
Underwater microphones pick up limited—and uniformly grumpy—"vocabulary."

Dave Mosher
for National Geographic News
Published October 12, 2011

Red-bellied piranhas (file picture) bark to warn away other fish, a new study says.
Photograph from Age Fotostock/Getty Images

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.

Now a fish tank, an underwater water microphone, and a video camera have helped uncover three different piranha calls—all tied to a variety of grumpy behaviors.

"We knew piranhas were able to make sounds but were not satisfied with the explanation for how they do it," said biologist Eric Parmentier of the Université de Liège in Belgium. "We wanted to know how they do this and what these sounds might mean to other fish."

Piranha Translator?
Twenty-five species of piranhas exist in the wild today, but only "two or three" species pose a threat to humans, Parmentier said.

In particular, the red-bellied piranha's voracious appetite for fresh meat is a big reason many scientists have shied away from studying any in-water vocalizations, he added.

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