Although piranhas have gotten the Hollywood treatment, they are truly only aquatic vultures rather than monsters of the deep. While Spectre famously killed off one Bond girl with voracious piranhas in You Only Live Twice, you should not fear. Piranhas have been shown to only nibble on humans once they are already dead. Even if piranhas feast on small mammals, it’s also usually postmortem. Science has effectively busted the man-eating piranha myth, but the myth persists somewhat.
Piranhas truly do have sharp, serrated teeth adapted for their carnivorous appetites that are much like shark’s teeth. That being said, a standard piranha diet is made up of crustaceans, fish, insects, worms, and carrion. Occasionally, if food sources are low and competition is high, piranhas turn to cannibalism to take a bite out of their friends: dead or alive. Of course, piranhas seem to fight stereotypes, and so some of them have been found to be vegetarians feeding only off riverweeds.
If you do happen to be taking a dip in the Amazon, it’s good to remember that piranhas like to be left alone. Much like bears, they are best when unprovoked. Although they have gained an intimidating reputation for swimming in packs, or shoals, in order to allow them to consume larger prey quickly, they truly only travel in large numbers for safety. They even swim in larger packs near the shore where they might be more vulnerable to other predators. That being said, piranhas are attracted to splashing, noise, and blood. So if you happen to start bleeding after indulging in a water fight, it’s best to get away from the water.
It might be Teddy Roosevelt’s fault that piranhas get a bad rap. After his journeys through South America in 1913, he wrote Through the Brazilian Wilderness. In his book he included a description of his encounter with piranhas:
They are the most ferocious fish in the world. Even the most formidable fish, the sharks or the barracudas, usually attack things smaller than themselves. But the piranhas habitually attack things much larger than themselves. 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; they will rend and devour alive any wounded man or beast; for blood in the water excites them to madness.
It’s a good thing Roosevelt isn’t known as the president who can’t tell a lie, as his harsh misrepresented of piranhas went on to be widely read and accepted.