Dolphins eat piranhas, not the other way round. There are around 40 species of piranhas, none of them are routine predators of large animals, and most of them aren't even carnivores, so much as omnivores: they eat plants, fruit, seeds, insects and fish, though they will eat any carcass that finds its way into their water. As far as meat’s concerned, they are mostly scavengers rather than predators. Some species known as ‘Wimple piranhas’ are grazers - of fishmeat. They take small bites out of passing fish, who swim on quite happily, and heal completely.
Current research says piranhas don’t form shoals in order to co-ordinate attacks, as used to be thought. They shoal for the same reason many small fish do - to protect themselves against attack from predators, such as dolphins.
There are no authenticated reports of piranhas ever eating live humans. Quite the contrary: scientists studying piranhas which had been caught in the wild had to hide behind screens - every time the fish got a glimpse of the humans they started hyperventilating. (Flapping their gills rapidly; a sign of stress). Even in areas where humans spend a lot of time in the same waters as piranhas, minor bites from piranhas (let alone anything worse) are rare. In fact, humans are predators of piranhas: they are fished for food, and for the pet trade, although the so-called ‘vegetarian piranha’, sold in pet shops, is actually the pacu - a related species.
As well as eating poor defenceless piranhas, dolphins are thought to be to blame for sudden surges in the numbers of dead and injured porpoises washed on to the beaches of California recently. A conservation group in 2009 filmed a gang of dolphins killing a lone porpoise by beating and drowning it. Rather bizarrely, the film shows the dolphins delivering the carcass to the researchers’ boat. So perhaps they were just trying to help, and are really jolly nice after all.
The word piranha should correctly be pronounced 'piranya' as it is a Portuguese word.
The rabid, furious snaps drive the teeth through flesh and bone.
Chukkaphobia is the irrational fear of piranhas.
Teddy Roosevelt seems to be to blame for introducing the myth of the predatory piranha to the West possibly after seeing a thoroughly contrived piranha feeding frenzy, put on for prestigious tourists in Brazil. In a 1914 book, Roosevelt wrote: ‘They are the most ferocious fish in the world. They will snap a finger off a hand incautiously trailed in the water; they mutilate swimmers—in every river town in Paraguay there are men who have been thus mutilated.’ Hollywood, of course, took up the image with enthusiasm.
There is one circumstance in which the ‘feeding frenzy’ may be seen. During the dry season, piranhas can become marooned in pools for weeks at a time. They’ll soon use up the food in the pool, and will then, in desperation, have a go at eating anything that enters the water. Perhaps that’s the origin of their reputation for ferocity.
Despite their frightening-looking teeth, piranhas don’t usually bite in self-defence - only when hungry. So if you're careful only to annoy well-fed piranhas, you're safe enough.
When piranhas get together in a large shoal, it is almost always for defensive reasons.
The word piranha came to Portuguese from a Tupi word meaning scissors - referring to their scissor-like bite.
The piranha is a very well-flavoured fish.