Ecological importance: The increase in attacks is related to human actions, such as the construction of dams. Piranhas are detritivores, that is, they feed on the remains of organic matter. For this reason they are important for maintaining the health of the rivers in the regions where they occur. Food: Piranhas are not top predators and always attack out of hunger or when they feel threatened. Despite their fame, many species of piranhas do not feed exclusively on meat, they also act as important seed dispersers. Dentition: The teeth are triangular in shape and pointed, connected to very strong jaws, capable of tearing off pieces the diameter of the piranha's mouth. Their dentition was not made for chewing, but for cutting and swallowing. So when a hungry school attacks, the prey quickly disappears.