How Do Piranhas Eat?

Updated April 17, 2017

Piranha are small fish with a big, flesh-eating reputation. A freshwater fish found in the rivers and lakes of South America, piranha grow to about 10 inches in length and are aggressive and efficient predators. Nature equips them with powerful fins, muscular jaws and two rows of interlocking razor-sharp teeth. Piranha also maintain a social structure that frequently determines how and when the fish feed.

Group Feeding

Newly hatched fish survive by feeding on plants and seeds while juveniles begin biting fins and scales of other fish. Adults hunt in groups of 20 to 30 fish called shoals led by one or two dominant fish that lead attacks on fish, crustaceans, reptiles or other animals. A dominant fish that attacks can trigger a feeding frenzy, or a group attack. Piranha smell blood and will swim from distances of up to 2 miles to join an attack. Piranha hunt at dawn and dusk. During the day, they hide among plants and wait for opportunities to ambush prey.

Piranha Prey

Piranha feed on the bodies of dead fish and animals and play an important role in keeping river and lake water clean. They hunt young, sick or injured fish and animals. They are less likely to attack a strong and healthy adult animal, but will do so if food is scarce. Piranha do not kill prey before eating it. They use their triangular-shaped teeth to tear off pieces of flesh, eating their victims alive. Piranha do not chew their prey's flesh, they swallow pieces whole.


Piranha sometimes gather in shallow areas under trees where birds nest to take advantage of young birds that can't fly and fall into the water. If necessary, they also feed on one another and their young. Cannibalism occurs during dry seasons when water recedes and the fish become trapped in small pools with limited sources of food. Dominant fish that attack other members of the shoal are both feeding and eliminating weaker members of the community.

Feeding in Captivity

Roughly 25 states either prohibit residents from raising and keeping piranha in aquariums, or require owners to acquire a special permit. Pet owners who keep piranha usually feed them three times a day. Newly hatched fish eat baby shrimp brine, blood worms and fish food flakes. Juvenile piranha thrive on small pieces of shrimp, frozen fish and small, live feeder fish. Some piranha owners feed adult fish a diet of live feeder fish, beef heart and small rodents such as newborn mice.

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About the Author

Laura Scott has been reporting for Gatehouse Media New England, Essex County Newspapers and other regional publishers since 1997. She won several New England Press Association awards for her coverage of the fishing industry and coastal communities. Scott is a graduate of Vassar College and has a master's degree in American studies from Boston College. She also attended art school in Italy.