The piranhas or pirañas are a group of carnivorous freshwater fish living in South American rivers. They belong to five genera of the subfamily of Serrasalminae (which also includes closely related herbivorous fish including pacus and silver dollars). They are normally about 15 to 25 cm long (6 to 10 inches), although reportedly individuals have been found up to 40 cm in length. They are known for their sharp teeth (able to bite through a steel fishing hook) and an aggressive appetite for meat and flesh. They are normally only found in the Amazonian, Guianas and Paraguayan river systems. However, piranha (most likely former aquarium-dwellers) are also occasionally found in the Potomac River, but they typically do not survive the cold winters of that region.
From the moment tiny baby piranhas hatch from their microscopic eggs, they come into the world armed and dangerous. Baby piranha will feast on tiny crustaceans, fruits, seeds, and aquatic plants. Once they reach about 1.5 inches in length they begin feeding on the fins and flesh of other fish that wander too closely. As they grow larger they begin to venture out in groups (schools) of about 20 fish where they use a variety of hunting strategies to kill and eat their prey. Heck, they don't kill their prey first, they just start eating the victim alive - that's what makes them so ferocious. Adult piranha have been known to eat their own babies. Talk about brutal!
When a school of piranha are in a feeding frenzy the water appears to boil and churn red with blood. They attack with such ferocity that they strip an animal of its flesh within a matter of minutes, even taking bites out of each other in the process. Adult piranha will eat just about anything - other fish, sick and weakened cattle, even parts of people. Sickly cattle that have stooped their heads down to drink from the river have been grabbed by the mouth and nose and pulled into the water, completely devoured minutes later. As wicked as it all sounds, piranha have a useful function in the Amazonian jungles just like any other predators in the wild. They are part of the checks and balances Mother Nature employs to eliminate the weak and sick so only the strong survive.
Piranhas are world-famous for their razor-sharp teeth. Native peoples of South America will catch the piranha and use their teeth to make tools and weapons. Even the fisherman who catch these vicious little predators have to be careful when the fish is out of water. A single piranha out of water is still dangerous enough to take off the flesh, or the odd toe, from an unwary fisherman.
But, piranhas generally pose no threat to humans. Natives frequently swim in piranha-infested water without attacks or scratches. However, it is not recommended to swim where piranha live in drought season because of increased aggressiveness caused by food scarcity and increased tendency to form large schools. Piranha fish also have the same sensory system that enables sharks to detect blood in minuscule amounts, so it is believed that swimming with an open cut may enhance the chance of an attack, yet Piranha fish rarely try to eat animals much larger than themselves.
