This Is What Happens When You Jump Into Piranha-Infested Waters

As you peer into the Amazon River, suddenly losing your footing and falling, you find yourself surrounded by piranhas swiftly approaching in the water. The question arises: are you in peril? Will your fall trigger a deadly feeding frenzy? To determine your fate, let’s explore what we know about these fish.

There are over 30 piranha species, all residing in South America’s freshwater habitats, equipped with a single row of sharp, interlocking teeth on each jaw. They employ these teeth in various ways, with many being omnivorous and supplementing their diets with insects, crustaceans, worms, and fish, as well as fruits, seeds, and plant matter. Some, like red-bellied piranhas, both hunt and scavenge, while others, such as wimple piranhas, have specific dietary preferences, primarily targeting other fish scales.

Redeye piranhas tend to be more solitary, while red-bellied piranhas form shoals of 10 to 100 individuals. Despite their common portrayal as highly aggressive, their reputation for cooperative pack hunting is somewhat misguided. The primary advantage of their group living seems to be protection from predators. Larger, mature red-bellied piranhas typically occupy safer positions at the center of the shoal, while those in smaller groups exhibit increased anxiety and faster breathing. Additionally, they communicate through specialized muscle contractions, producing various sounds during confrontations, feeding, and competition, possibly serving additional purposes during mating.

So, when do red-bellied piranhas become aggressive towards humans? Incidents of biting humans mostly occur when they are handled, when individuals inadvertently introduce food or clean fish in the water, or when humans disrupt piranhas during mating or while guarding their eggs in the wet season. Starvation stress can also lead to bolder, more aggressive behavior, potentially resulting in feeding frenzies when food enters the water, although such behavior is extremely rare.

The international infamy of piranhas, including rumors of feeding frenzies, can be traced in part to former US President Theodore Roosevelt, who sensationalized them in his 1914 bestselling book. He referred to piranhas as “the most ferocious fish in the world” and claimed they could rapidly devour an entire cow or human alive upon detecting the scent of blood. However, Roosevelt’s account is widely regarded as circumstantial and misleading, likely orchestrated for spectacle by starving red-bellied piranhas and providing them with a cow carcass.

Returning to the scenario of falling into piranha-infested waters in the Amazon River, your fate appears relatively safe. Assuming these are red-bellied piranhas and considering the ample resources in the Amazon, starvation is unlikely. Thankfully, you’re not plunging into the water amid fish guts, nor are you disrupting a piranha breeding event. In all likelihood, as you calmly and gently swim or wade to shore (as splashing can attract piranhas), the piranhas will probably steer clear of you. While they possess formidable teeth, they rarely attack humans, typically having more preferable food sources. As you make your way onto dry land, there won’t be a frenzied skeletonizing of your body within minutes, and you’ll likely find no missing chunks of flesh upon exiting the water.