If the movies are to be believed, you only have to dip a toe into an Amazonian tributary to risk having the flesh stripped from your bones by pack-hunting carnivorous fish - usually piranhas.
What is a piranha?
The name ‘piranha’ covers several species of South American freshwater fish belonging to the Serrasalmid family. As a rule, they are opportunistic omnivores rather than specialist carnivores – meat, carrion, vegetation, nuts, fruit and seeds are all on the menu.
Can piranhas actually kill a human?
With razor-sharp teeth and the strongest bite force recorded for any fish, their fearsome reputation is not entirely undeserved.
Some species are quite capable of taking a chunk out of a person or snipping off a finger or toe. The vast majority of attacks, though, involve just a single bite, and they seem to be more likely when swimmers disturb the fish’s nest on the riverbed.
Whether piranhas ever actually kill humans is far from clear. They do form shoals, but this seems to be more about seeking safety in numbers than hunting bigger prey in packs.
There are certainly a few documented cases of human bodies being eaten by piranhas. But it’s always hard to know if the victims were already dead when the piranhas found them.
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