Are Piranhas Man-eaters?

If you were to fall into the Amazon River, are you doomed to be eaten by piranhas? Piranhas can be pretty ferocious, and we've all seen those demonstrations where a meaty bone is offered to a school of piranhas and they go to town, churning the water until it's bloody. Teddy Roosevelt wrote about piranhas after a South American trip, describing how they consumed an entire cow before his eyes, and would likely do the same to a human. A century of research has raised questions about that demonstration, but the piranha became a terrifying symbol of the dangers of the Amazon just the same. Learn about piranhas and the danger they pose in this this TED-Ed lesson.