FaunaHub

Piranha (e.g. Pygocentrus nattereri)

FishFreshwaterSouth America

Red-bellied piranha (Pygocentrus nattereri) showing its deep body and reddish belly.

Red-bellied piranha (Pygocentrus nattereri).

Image: H. Zell, CC BY-SA 3.0, via Wikimedia Commons.

Overview

Piranhas are freshwater fish of South American rivers and lakes, famous for their sharp, interlocking teeth and powerful bite. There are many species; the red-bellied piranha (Pygocentrus nattereri), shown here, is the best known. They have deep, laterally compressed bodies and strong jaws built for shearing.

Despite a fearsome, film-fuelled reputation as frenzied flesh-eaters, piranhas are mostly omnivores and scavengers, and many gather in groups largely for protection from predators rather than to launch attacks.

Note: piranha species vary in diet and behaviour, and most popular “man-eater” stories are exaggerated. Treat general statements as approximate and verify against authoritative sources.

Habitat & Range

Piranhas live across much of tropical and subtropical South America, in rivers, streams, floodplains, lakes, and reservoirs — including the Amazon and Orinoco systems. They favour warm fresh water with vegetation or structure, and their numbers and behaviour shift with seasonal flooding and drying.

Diet

Many piranhas are omnivores, eating fish, insects, crustaceans, fallen fruit and seeds, and scavenging dead or dying animals. Some species are more predatory and others more plant-leaning. Their teeth are well suited to taking bites — including nipping the fins or scales of larger fish, which can heal.

Behavior

Piranhas often live in groups (shoals). Research suggests this shoaling is driven more by safety from their own predators — such as larger fish, birds, caimans, and river dolphins — than by cooperative hunting. They communicate with sounds (including barks and croaks) and can be wary, fast-moving fish. Feeding can become intense when food is scarce or concentrated.

Human Interaction & Conservation

Piranhas are an important part of South American river ecosystems as both predators and scavengers that help recycle dead matter. Serious attacks on people are rare and usually linked to unusual conditions; the common image of piranhas stripping animals in seconds is largely a myth. They are also fished for food and kept in aquariums (where legal). Consult authoritative sources for specifics.

More photos of the piranha

A red-bellied piranha in profile.

Red-bellied piranha (Pygocentrus nattereri).

Image: Gregory Moine from Niantic, USA, CC BY 2.0, via Wikimedia Commons.

Frequently Asked Questions — Piranha

Are piranhas dangerous to humans?
Far less than their reputation suggests. Serious piranha attacks on people are rare and tend to happen in unusual situations, such as very low water that crowds and stresses the fish, or near fish-cleaning waste. Bites do occur but the popular image of piranhas rapidly devouring people or large animals is largely a myth.
What do piranhas actually eat?
Many piranhas are omnivores and scavengers, eating fish, insects, crustaceans, fruit and seeds, and carrion. Some species lean more predatory and others more herbivorous. Notably, some piranhas feed by nipping fins or scales off larger fish, which often survive and heal.
Why do piranhas swim in groups?
Studies suggest piranhas shoal mainly for protection from their own predators — larger fish, birds, caimans, and river dolphins — rather than to hunt cooperatively. Living in a group provides safety in numbers, which is important because piranhas are themselves common prey.
How many kinds of piranha are there?
There are many piranha species across South America, varying in size, diet, and temperament. The red-bellied piranha is the most famous, but the group as a whole is diverse and not uniformly aggressive.

Sources and further reading

Authoritative wildlife references used for general educational context. Conservation status should always be verified against current IUCN Red List data. External links open in a new tab.