One of many memorable scenes in Fredrick Forsyth’s thriller Avenger (which I’ve listened to three times!) occurs when the hero spends several days scouting the encampment of the villain and sees a stream running along the property, an obstacle he’ll have to cross to get inside. Every day, a worker comes out and throws chickens into the water, which are immediately devoured in a frothing mass of piranhas. Eeeew.
But, do piranas have a bad rap? Before you decide, or before authors enlist them to be aggressors in their fiction, you and they might check out Ronald B. Tobias’s article, “Roosevelt’s Piranhas” in the February 2025 issue of Natural History. Piranhas acquired their deadly reputation after Teddy Roosevelt made a trip to Brazil and observed piranhas devour an entire cow in minutes with their razor-sharp, blade-like teeth. What he didn’t know was that this demonstration had been carefully staged for maximum mayhem. He was “the victim of a hoax,” Tobias writes.
A few factoids: most of the 30 to 60 piranha species are vegan; a piranha can detect a drop of blood in 50 gallons of water; they keep rivers clean by “disposing of” dead or dying animals; the bite of a fully grown black piranha is, pound for pound, more powerful than that of the Tyrannosaurus rex; Latin Americans eat them to treat problems of sex drive (men) and reproduction (women); they’re banned in 27 US states, where officials worry they might escape into the wild and breed—piscine pythons.
The red-bellied piranha, called Roosevelt’s Piranha, is about a foot long and weighs three pounds. It’s not so big, but it’s the numbers that will get you. They travel in shoals that can include hundreds or even thousands of fish. For the most part, they are relatively harmless, “except for a few scary weeks of the year,” Tobias says. In the wet season, the river waters flood vast areas, where many animals live, and fish food is plentiful. As the land dries up again, all these well-fed fish are channeled back into a much shrunken area, trapping predator and prey. Once that limited food supply is gone, the fish attack each other—“the cannibal fish Roosevelt saw in Brazil.” That is definitely not the time to take a swim. As the water polo team in Wednesday Addams – Piranha Pool learned.
