Piranha 'less deadly than feared'
experts from St Andrews University say that piranhas are omnivores who mainly eat fish, plants and insects.
They form large groups not to hunt but to defend themselves against other predators, the team said.
Piranhas can be attacked by dolphins, caimans and other large fish, and forming a shoal is their way of avoiding being eaten
clipped from: news.bbc.co.uk 