The piranha"s bad reputation is more than just a bit excessive and extreme. Most of it is actually due to the 26th president of the United States, Theodore Roosevelt"s unbelievable description. After returning from a trip to South America, Roosevelt described the piranhas he witnessed as: "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. They will snap a finger off a hand incautiously trailed in the water; they mutilate swimmers—in every river town in Paraguay there are men who have been thus mutilated; they will rend and devour alive any wounded man or beast; for blood in the water excites them to madness. They will tear wounded wild fowl to pieces; and bite off the tails of big fish as they grow exhausted when fighting after when fighting after being hooked."This is largely due to how the locals put on a show and exaggerated the brutality of piranhas. Since the locals knew that the famous Roosevelt was coming, they wanted to put on an incredible show for him. They decided to section of a part of the Amazon river and then caught and transferred piranhas to this part of the river. The fish were then left to starve until the day Roosevelt came by. On that day, they "appeased" the fish by sacrificing a live cow. The starving fish naturally shredded the cow causing the water to foam and turn red. Roosevelt naturally just a.s.sumed that they were born killing machines and described how they looked evil and ferocious.
Although piranhas have sharp teeth and most of them are carnivorous, they usually avoid larger animals. They instinctively act like fish and avoid larger fish by all means. Humans are only ever targeted if they are either dying or dead. The most that will happen is a few bites. Around 500 piranhas would still take 5 minutes to strip the flesh off a human. And the main reason piranhas move in packs is for safety and there have never been any reported cases of death by piranhas.
As already mentioned, not all piranhas are carnivorous and some are even vegetarians. Those mainly live off seaweed or riverweeds.
Interestingly enough, piranhas can create bark like noises.
Ps: They taste great