Piranhas attack crocodiles

Are piranhas really that dangerous?

Piranhas are popular cannibals in movies. But wrongly. The fish are actually peaceful. At least if there is no reason to worry.

Mr. Hasselmann, the remake of a horror classic will start in cinemas on August 26th: Piranhas. The legends about the bloodthirstiness of these predatory fish go back not least to Humboldt, who described how piranhas attack people in Brazil while bathing and tear out the meat. Are these reports correct?

I wasn't there then, but piranhas are actually quite peaceful. Especially towards humans, because we do not belong in their prey scheme. It is safe to swim in waters where piranhas live. Here in the aquarium we climb into your pool to clean the panes. And we are not attacked and eaten on the spot ...

... what you can already see from the fact that you are still alive ...

Correct. Rather, our piranhas are then the biggest fearful rabbits and hide themselves. Only once, when we were moving young animals with a cash, someone really bit my hand. Piranhas do not have great bite force, but they have razor-sharp teeth with which they cut into the meat like a saw.

But are piranhas just as reticent in the wild?

Well, when they are under stress or the males are guarding their brood, piranhas can bite quite aggressively, and when they are very hungry, they can gnaw an animal in the swarm to the bone. There is a TV documentary showing how a meter-long anaconda slides into such a river. It is skeletonized within a few minutes.

Was she hurt so that the fish could smell her blood?

It is true that piranhas, like sharks, perceive the smallest traces of blood. But under stress they also attack uninjured animals. For example, in the dry season when the water level is low, when only brackish ponds remain from the river. Then the oxygen content in the water drops and the temperature rises. If the food runs out, piranhas even pounce on their fellow species.

Do you attack each other?

Yes, if a piranha shows weakness, it only does it once. We have already noticed this in our swarm of 15 animals. We used to have over 30 animals, we didn't give them all away or we didn't die on their own.

Piranhas are not that harmless after all.

They are more dangerous than other fish of the same size without teeth. But I would definitely be more afraid of a crocodile. It should also not be forgotten that they play an important role in the ecosystem. They eat dead and sick animals before they contaminate the water. Piranhas are a kind of health police - just like the hyenas and vultures in the savannah.


Marco Hasselmann is the district manager of the freshwater department at the Berlin Aquarium. He says piranhas aren't all that dangerous - unless they're stressed.

© natur.de - nature editorial team
August 30, 2010