Red-bellied piranhas are named for their red undersides.
Red-bellied piranhas are named for their red undersides.
Photograph by Prillfoto, Dreamstime

Red-Bellied Piranha


Red-bellied piranhas live in lakes and rivers in South America. They sometimes use their mighty mouths to gobble up other fish or animals such as shrimp, worms, and mollusks. They swim and hunt in shoals, or schools, that can include more than a hundred individuals. According to legend, the animals, which can grow about 14 inches long, have even devoured human swimmers.


Despite their big bite, scientists believe that the animals’ fearsome reputation has been exaggerated. Researchers think that these fish swim in groups for protection, not to carry out underwater takedowns . And reports of the fish going after humans are extremely rare.

When some red-bellied piranhas do get aggressive, they have an interesting way of telling others to "back off"—they make bark-like sounds! Guess these guys are all bark, and just some bite.