The red-bellied piranha is a fish of South American rivers. Its belly is red, and its gray body is flecked with silver. It lives in the Amazon River basin, the Paraguay-Paraná River basin and rivers of northeastern Brazil. It likes warm water, about 25 degrees Celsius. A red-bellied piranha grows to about a foot long and can weigh up to 4 pounds, or 1.81 kilograms.

Smaller red-bellied piranhas look for food in the day. Larger ones look for food at dawn, in the late afternoon and in the early evening. They eat other fish, shrimp, worms, insects, snails and other mollusks. In the wild, a good portion of their diet is fins nipped from the tails of larger fish. You may have heard that piranhas only eat meat. In fact, they also eat plants and fruit. They are also scavengers in the Amazon basin.

Red-bellied piranhas live in big groups called shoals. A shoal can have more than a hundred fish in it. They tend to travel in schools of 20 or more. You may have heard that piranhas hunt in packs. In fact, they gather in shoals for protection rather than hunting their prey in packs. A shoal is a way to stay safe.

A piranha has rows of sharp teeth. It replaces its teeth through life, one side of the jaw at a time, so it can keep feeding. Male red-bellied piranhas build nests in the mud and sand at the bottom of the water. A female can lay thousands of eggs. The eggs are laid in clusters and stuck to plants growing under the water. A red-bellied piranha can live about 10 years.

Words to know

• shoals: fish groups
• mollusks: snails and clams
• scavengers: leftover eaters
• dawn: first light
• basin: river land