In 1914, former US President Theodore Roosevelt was traveling in Brazil when local residents staged a demonstration of sorts. They barricaded a school of piranhas on the river bank and then starved the fish for several days. While Roosevelt watched from the riverbank, they pushed the cow into the water to show how quickly it was devoured by the piranhas.
Roosevelt told this story in a book and also stated that piranhas attacked helpless people. Readers were horrified, and piranhas were long considered cannibalistic monsters.
In recent years, scientists have analyzed the mechanism of the piranha's brutal bite and determined which parts of Roosevelt's claims were true and which were fiction.
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Piranha Jaw Strength
In response to Roosevelt's book, a renowned zoologist wondered whether piranhas even existed, according to the Theodore Roosevelt Center. Small fish and their deadly force of jaws seemed outlandish.
Species of piranha such as black piranha (Serrasalmus rhombeus)however, as strong as Roosevelt promised. 2012 study in Scientific reports measured the bite force of a black piranha to be 320 Newtons or 70 pounds.
How can someone so small fish Do you have such a powerful jaw? Scientists now have a better understanding of how the piranha's unique shape contributes to its powerful bite. The piranha's body is disc-shaped, which gives them room for a larger jaw as well as room for the jaw muscles to move.
“This available space on their skulls, which piranhas have more than other fish of the same size, allows for greater area of attachment and movement of the jaw muscles,” says Robert May, an aquarist at the Long Island Aquarium who curates the piranha exhibit that houses red-bellied piranhas (Pygocentrus natteri).
Piranhas also have adductor muscles in their jaws, which work together with other muscles so that the greatest bite force comes from the back teeth. May says this allows piranhas to “clench their jaws with incredible force.”
Very sharp piranha teeth
In his book, Roosevelt claimed that a school of piranhas deprived a cow of meat and muscle in a matter of minutes. This event was staged, so the piranhas were hungry, anxious and aggressive. But their teeth are indeed capable of tearing the flesh of animals and quickly devouring it.
Piranhas have tightly packed teeth, which helps them chew food quickly. Because they have a large head surface, May says the teeth are spaced throughout the jaw in a way that allows them to avoid biting themselves while chewing.
Combined, the piranha's jaw strength and sharp teeth are so powerful that if it were larger, its bite would be comparable to that of some apex predators.
“So, although large modern sharks and alligators have greater bite force than piranhas, if there were a piranha the same size as these large sharks and alligators, then the piranha's bite force could certainly rival others,” May says.
Although piranhas have a powerful bite force and knife-like teeth, many of the piranha's potential prey have evolved to acquire protective armor.
In a 2023 study in Integrative biology of organismsresearchers observed captive red-bellied piranhas as they attempted to hunt three-lined corydoras (Corydoras trilineatus). The three-lane corridors had natural armor that often withstood piranha attacks. They survived 37 percent of bites without injury, and it typically took nine strikes for the piranha to impale its prey.
Piranha's fish reputation
Not every bite is a quick kill, but piranhas have earned a reputation as man-eaters similar to the bad reputation sharks have received.
“These are not the flesh-eating machines that Teddy Roosevelt's treks through the Amazon rainforest or Hollywood movies would have us believe, although they do generally eat meat in spectacular fashion,” May says.
Horror stories of people swimming in rivers being attacked by piranhas are not supported by science, and a study of aquatic animal injuries in Brazil found that 88 percent of injuries were caused by bites from fish such as stingrays or jellyfish, according to a study conducted in Journal of the Brazilian Society of Tropical Medicine.
Although it may seem that piranhas might rush to attack people as soon as they notice their presence, well-fed piranhas are not particularly interested in people. For example, at the Long Island Aquarium, an aquarist regularly enters the piranha habitat for cleaning and maintenance. The piranhas keep their distance and seem relieved when the person finally leaves.
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Article sources
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