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The Debunker: Will Piranhas Strip Off Your Flesh?

by Ken Jennings

“I had this story from one who had no business to tell it to me, or to any other.” On August 27, 1912, these words in the new issue of All-Story Magazine heralded the first appearance of a new fictional hero: Tarzan, Lord of the Apes. “A crackerjack!” enthused the magazine. “It is the most exciting story we have seen in a blue moon… Zowie! but things happen!” A century later, Tarzan is still going strong. In honor of the ape-man’s 101st birthday this month, we’ve asked Jeopardy! know-it-all Ken Jennings to swing in on his vine and debunk four longstanding misconceptions about the jungles of the world. Ungawa!

Jungle Myth #1: Piranhas Will Strip Your Flesh from Your Bones!

Most people probably know exactly one thing about the small South American fish called piranhas: they are a swarm of razor-toothed juggernauts that will turn the unwary river traveler into a bleached cartoon skeleton within seconds! As a result of the media hype, piranha attack is now a horror and action movie staple. And after a century of panicky species misidentifications, the fish is now banned in over twenty-five U.S. states.

But reports of the piranha’s bloodthirsty appetite have been greatly exaggerated. Most adult piranha survive on fruit, and even the most feared species, Pygocentrus nattereri, the red-bellied piranha, is mostly a scavenger, preying on decaying river carrion, not fresh meat. In 1976, Herbert Axelrod, chairman of the Exotic Fishes Committee of the American Fisheries Society, wrote, “In twenty-five years of travel and fishing in almost every river system in South America, nearly all of which had schools of piranha, I never was bitten, nor did I ever meet anyone who was bitten … nor did I ever meet anyone who even knew anyone who was bitten by a piranha … and these are mostly Indians who live on the river and swim in it every day.” A 2003 study demonstrated that piranha travel in schools as a defense against predators, not because they are marauding for flesh.

So where did the piranha get its badass reputation? Blame Teddy Roosevelt! In 1913, the ex-president mounted an expedition into the Amazon rainforest, up the so-called “River of No Return.” Roosevelt’s Brazilian hosts hoped to impress him with the ferocity of the local fauna, so they staged a piranha attack. They starved a reservoir of the poor fish until they were devouring each other from hunger, then herded a sickly old cow with a bloody discharge into their midst. The resulting carnage was vividly described by Roosevelt in his book Through the Brazilian Wilderness, and a legend was born. Take note: piranhas do have sharp teeth and will try to chow down on living flesh as a defense mechanism or if they’re very hungry. But typically, swimming is piranha-infested waters is perfectly safe. The fish you really have to watch out for is the candiru, which has a reputation for swimming all the way up—well, just go Google it.

Quick Quiz: What now-megasuccessful movie director made his ignominious debut on the low-budget 1981 film Piranha II: The Spawning?

Ken Jennings is the author of Because I Said So!, Brainiac, Ken Jennings's Trivia Almanac, and Maphead. He's also the proud owner of an underwhelming Bag o' Crap. Follow him at or on Twitter as @KenJennings.