The Feeding Behavior of Piranhas, Explained

Piranha is a general name used to describe a group of freshwater fish with a fearsome reputation when it comes to feeding. There are between 40 and 60 different species; none grow larger than two feet in length. All of them live in South America, but there are isolated reports of them being spotted in other parts of the world. Are these fish the ruthless predators that we have seen in movies? Let’s look at the facts about piranha feeding behavior.   

Piranha Diet

The truth about the piranha diet is far removed from the feeding frenzies you have seen in video clips and movies. Some piranhas do not even eat meat at all – they are herbivores. Others are omnivores and are just as partial to seeds as they are to fresh flesh.

However, at the other end of the scale, there are some piranha species with deadly features that allow them to be highly effective predators. For example, the black piranha, Serrasalmus rhombeus, has the strongest bite force of any bony fish and has been measured as 320 N. This means that an eight-inch fish can exert a bite force that is equivalent to 30 times its body weight. Size for size, it is three times as powerful as that of an American alligator thanks to huge and strong muscles and tendons around its mouth. Carnivorous piranhas typically have rows of 6–7 serrated, multi-cusped, triangular, blade-like teeth—perfect for biting.

What Do Redbelly Piranhas Eat?

The redbelly piranha (Pygocentrus nattereri)  is one of the more aggressive piranha species, but it is also an omnivore. They are typically found in white water streams in South America. The larger individuals hunt for food at dawn, late afternoon, and early evening by lurking in groups of 20 or 30 in vegetation and launching ambushes on prey. However, they have also been seen chasing prey and scavenging. They pick at the fins and scales of fish (using their specially adapted teeth) or eat the whole fish. While they are scanning for fish to prey on, they will also eat snails, insects, and plants.

What Do Wimple Piranha Eat?

Wimple piranhas (Catoprion mento) have everted (outward-pointing) teeth and jaws that open to more than 180 degrees, which makes them perfect for scraping scales off other fish. It’s not surprising, therefore, that their diet mainly consists of fish scales with some plant material (including root wads), some algae, and the occasional aquatic beetle larva.

Piranha Diet – The Big Picture

While there are variations in diet between the different piranha species, many of them have fish as a major component. This can be flesh, fins, scales, or the whole fish. Some species are more generalized, but others have highly specialized mouths to eat just fish scales. Accounts of piranha feeding frenzies are largely exaggerated. These fish mainly gather together for protection. That said, they are opportunistic hunters, and if an injured or dead mammal were to fall in the water, they would not let the opportunity pass them by. They eat more aggressively when food is in short supply, and they can also eat very quickly.

Humans are not the natural prey of piranhas, so we have little to fear from them. However, there are a few documented cases where they have attacked a human body and eaten it. In these cases, the unfortunate person had already died from another cause, and it was not the piranhas that killed them. The majority of piranha bites on fit and healthy human swimmers have been attributed to fish defending their broods rather than hunting for their next meal.

Feeding Pet Piranhas

Piranhas only make good pets in special circumstances. They may be beautiful, but many species are aggressive and cannot be kept with any other fish because they will eat them – that includes other piranhas!  If you are purchasing a piranha because you want to see a feeding frenzy, you are likely to be disappointed, as they are more likely to take swipes at their food rather than engage in frenzied feeding.

The best option is to feed them commercially prepared fish flakes, pellets, and granules. You can also feed them frozen krill. It is not a good idea to give them things like chicken or beef because they contain fats that piranhas cannot metabolize, and this will cause health issues over time. Feeding them live fish can also be problematic, as it can introduce pathogens into your tank.