Despite frequently being portrayed as a dangerous and unpredictable predator, the red-bellied piranha feeds mainly on fish, insects and aquatic invertebrates, such as molluscs and crustaceans. It may also feed on any small, terrestrial animals it encounters, as well as fruits, seeds, algae and aquatic plants (2) (4) (5) (6). The sharp, triangular teeth of the red-bellied piranha interlock when the mouth is closed, making it extremely efficient at biting through food items (3) (8) and its powerful jaw arrangement and flat, blunt snout give the fish the ability to attack and bite with remarkable force.
The red-bellied piranha lives in shoals, although it does not exhibit group hunting behaviour (7). Occasionally the red-bellied piranha will enter into a ‘feeding frenzy’, where schools of piranha converge on a large item of prey and strip it clean within minutes. This particular behaviour contributes to the formidable reputation of the red-bellied piranha, but the frenzies are not usually random attacks, and are more often the result of provocation or starvation (4) (5).
Breeding occurs during the rainy season, usually peaking over a two month period that can vary depending on location (4) (5) (6). The female lays around 5,000 eggs on newly submerged vegetation (6), often in bowl-shaped nests that have been built by the male (2) (4).