Piranha attack results in injuries. A school of wild fish attacked tourists at the Taruma Acu resort near Brazil's Amazon River, leaving at least eight people injured.
The fish with its sharp teeth tore the feet of bathing tourists. Experts argue that this is a case of mistaken identity. Chances are, the piranhas actually prey on the food that diners at local restaurants sometimes throw into the river.
"Piranhas do not exhibit unprovoked attacks on humans. The situation is one piranha is used to free food and the bite is just another example of mistaken identity, like a shark attack," said Steve Huskey, professor of biology at Western Kentucky University.
Several piranha species, including the red-bellied piranha (Pygocentrus nattereri), engage in a co-prey frenzy. "Species of the genus Pygocentrus, living in the Amazon and Sao Francisco river basins, are the most dangerous," said Paulo Andreas Buckup, professor of the National Museum of the Federal University of Rio de Janeiro.
But this behavior only occurs in exceptional circumstances, such as when a large number of fish are trapped in a small pond or starved for an extended period of time. "These fish swim in schools and don't usually attack large animals," Buckup said.
The majority of piranhas are harmless, tending to scavenge rather than hunt live animals. "Some species of the piranha family eat only fruit, insects and vegetables. Some specialize in eating fish scales and biting off the fins of other fish," Buckup said.
But the presence of people bathing where they eat can cause confusion and aggression. The attack on Taruma Acu could have been triggered by a piranha mistaking a leg for food, biting it and then making other piranhas join the prey.
"Attack is most likely caused by blood in the water, skin injury, or movement that looks like the fish is in distress. Because their teeth are so sharp, a single bite can cause a lot of bleeding and trigger a feeding frenzy," Buckup explains.
When feeding begins, piranhas dart in and out to bite their prey at high speed to avoid being bitten by other individuals. Piranhas have the strongest bite recorded on bony fish, being as tough as great white sharks