The reason why piranhas can strip a large animal like a cow down to a skeleton so quickly is because of a few factors. First, piranhas don’t chew. When they bite down, the big chunk of flesh they take out of the cow goes right into their bellies. They just keep snapping their jaws shut and filling themselves up. Next, that type of task is accomplished by hundreds of piranhas, not just the typical school size of 20, and piranhas are very efficient team eaters. In a feeding frenzy, they rotate continuously, so as each piranha takes a bite, it moves out of the way so the piranha behind it can get a bite, and so on. They take turns with incredible speed, which is where the boiling-water effect comes from. The piranhas are constantly changing position during a feeding frenzy. Even though piranhas are small, they’re seldom eaten alive by other fish. That razor sharp bite would really hurt going down. But piranhas are eaten regularly by herons and caimans (small gatorlike creatures) during the dry season, when water levels are low and piranhas end up trapped in small pools with no food. When they lay dying and unable to defend themselves, the herons and caimans — who had watched the piranhas eat their defenseless young during the wet season — come in and finish them off. Read More »