Red-bellied piranhas are gray with pronounced black spots at birth and develop their signature red undersides as they reach adulthood. They live in large groups called shoals. Typically, the younger piranhas are found toward the outside of the group and the larger, sexually mature adults are the center. This placement protects the adults from predators while giving the young easy, constant access to food. Piranhas have a reputation for aggressively swarming. In reality these attacks generally happen only if the prey is already injured.
These South American fish are found in the Amazon River basin and other freshwater rivers and streams in the area.
Red-bellied piranhas feed on other fish as well as insects, worms, crustaceans, mollusks, carrion, plants, seeds, and fruit.
Adult piranhas are approximately 12 inches long and can weigh up to four pounds. A piranha’s lifespan is up to 10 years.