Can Piranhas Smile?

By Amir BalvinLast Updated July 25, 2020
Photo Courtesy: Staffan Widstrand/Getty Images

Piranhas have a reputation for being some of the more ferocious fish in the world. If you take one look at their spiky, razor-sharp teeth, you might just believe that myth. As it turns out, piranhas could be some of the most misunderstood fish in the world, too.

Yes, they do attack humans from time to time, although the result usually isn’t fatal. Some of the more than 20 species of piranhas are even vegetarian; just one, the red-bellied piranha, tends to sometimes set its sights on human flesh. This only happens when they're extremely hungry and can't find other fish and animals to dine on. Like their feeding habits, whether or not these mysterious fish smile is also a topic for debate.

Where Do Piranhas Live?

Unless you live in South America, you're not likely to encounter a piranha in the water. Most of them live in freshwater lakes and rivers. While they're mostly found in the Amazon River, they also inhabit the Orinoco River Basin in Venezuela up to the Paraná River in Argentina. These fish play a vital role in local ecosystems, keeping the rivers on the continent clean by eating sick and injured animals.

Photo Courtesy: Yiming Chen/Getty Images

Studies have shown that piranhas have lived in South American river basins for tens of millions of years. Any type of piranha found in the wild outside of South America is likely an exotic pet that someone released into a larger body of water.

The Piranha's Reputation

While most piranhas prefer to eat smaller fish, insects and mollusks, legend has it that when these tiny creatures attack, they can rip large portions of flesh from a human and have even attacked cows in the past. But Popular Science reports that it would take 300 to 500 piranhas to rip the flesh from a 180-pound human in five minutes. Some species of the fish are total vegetarians and only feed on plants, nuts and fruits.

Photo Courtesy: Marc Guitard/Getty Images

Smithsonian Magazine has credited U.S. President Theodore Roosevelt with spreading the legend of piranhas’ supposedly monstrous behavior. After touring South America in 1913, he wrote, "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."

Roosevelt also reported watching piranhas devour an entire cow in mere minutes. However, the reason for their hunger has been debunked — sort of. At the very least, it doesn’t represent typical piranha behavior. Locals who welcomed the late president had stored the hungry fish in a tank without feeding them for a period of time before putting them in the water with a dead cow. They were extra-ravenous and appeared to be much more vicious while eating than they typically are.

Do Piranhas Really Smile?

You may have heard someone say that piranhas smile, but that's not accurate. Because of its teeth, it may look like a piranha is smiling as it swims through the water with its mouth open. But, unlike humans, there is no joy, happiness or other emotion behind the smile. It's simply the way the fish looks with those pointy teeth and an open mouth. The piranha's teeth are structured similarly to a shark's and, throughout its lifetime, the fish loses those teeth and new ones replace them.

Photo Courtesy: Dan Bradenburg/Getty Images

While it may seem like a piranha is smiling, happily awaiting its next attack with a sinister smile that rivals the Joker’s, in reality, the fish are fairly shy and laid back. They're generally scared of humans and prefer not to be startled. Those that live in the Amazon seem to only attack people during the dry season when other sources of food are scarce and they're desperate for a meal.

If you opt to swim in an area where piranhas live, avoid splashing around if you don't want to get bitten. When the fish can't find other food sources, they may wait for nuts and fruits to drop into the water and mistake your hand or foot for one. Like sharks, piranhas can also smell blood well — a single drop in up to 200 liters — so don't swim if you have an open wound.