How Sharp Are Piranha Teeth?

It's easy to picture piranhas as hungry teeth with fish attached. In fact, 'piranha' translates to "tooth fish" in the language of Brazil's Tupi people, according to Live Science. Paired with a prominent underbite, those notorious chompers make for a menacingly serrated smile. And if a certain rough-riding president is to be believed, when piranhas flash their pearly whites, get ready to see red because they will bite right through whatever unfortunate animal becomes the object of their hunger.

During an expedition in Brazil, as IFLScience describes, Teddy Roosevelt watched frenzied piranhas strip the flesh off of an old cow. Locals had shoved the bovine into the "River of Doubt," (now known as the Roosevelt River) to make the point that those fish have extremely pointy teeth. Without a doubt, he was thoroughly convinced. In his 1913 work, Through the Brazilian Wilderness, Roosevelt declared piranhas "the most ferocious fish in the world" and "the embodiment of evil ferocity." He further asserted that "they will rend and devour alive any wounded man or beast; for blood in the water excites them to madness." 

However, Roosevelt might have oversold the whole "evil ferocity" thing. So, just how sharp are a piranha's mouth knives?

When addressing the question of how sharp a piranha's teeth are, one should first ask, "which kind?" Live Science points out that between 40 and 60 species of piranhas exist and not all of them thirst for your blood. In 2016, the site reported on vegetarian piranhas that have square-shaped teeth which look strikingly human-like. Others have omnivorous diets and will eat seeds along with their hunks of flesh.

Per How Stuff Works, a typical piranha's teeth measure about a quarter-inch (4 millimeters) in length and interlock "like dozens of razor-sharp scissors." The most aggressive breed of meat-eater is the red-bellied piranha that inhabits the Amazon River. They can certainly snap off human fingers and toes with their razor-sharp teeth but generally live as scavengers rather than embodiments of evil ferocity.