Red Piranha (Pygocentrus nattereri)
Red piranhas are native to the Amazon Basin, coastal rivers of northeastern Brazil, and the basins of Paraguay and Parana.
Despite their voracious carnivorous reputation, the fish are primarily scavengers and foragers. During the rainy season, when food is abundant, they will mainly eat plants, debris, crustaceans and insects. Notwithstanding, they will eagerly feed on dead, injured or dying animals in the wild. They are also known as ambush predators, waiting in dark areas for unsuspecting prey to pass.
Piranhas tend to travel in shoals, but do not exhibit group hunting behaviour. Instead larger numbers offer them protection against predators. On very rare occasions, a feeding frenzy may occur when schools of hungry piranhas eat one large prey within minutes.
C Simmons on Flickr