The word piranha literally means “tooth fish” in the Brazilian language Tupí. Beneath the piranha’s snub-nosed profile and ‘high forehead’ are powerful muscles attached to a short, stout lower jaw. This design helps piranhas bite down with relentless force and scissors-sharp shearing ability. When its jaws snap shut, the top and bottom teeth interlock neatly like a trap. Covered by thick, fleshy lips, these rows of formidable teeth are not usually visible.
'Sharks' of the Amazon
Piranha teeth are razor-sharp and replaceable. Sharper than those of a shark, piranha teeth were used by local people as tools to cut wood and hair. The triangular shape of a piranha’s tooth is frequently compared to that of a blade and its tooth enamel structure is similar to that of sharks. Like sharks, piranhas lose and replace teeth throughout their lifetime. But while sharks replace their teeth individually, piranhas replace theirs in quarters. It isn’t uncommon to find a piranha with half of its lower jaw teeth missing.
Anecdotal accounts of red-bellied piranhas making barking noises when caught by fishermen have been verified by scientists, who’ve identified three distinct sounds. In a visual staring contest with another fish, a piranha may start off with quick warning calls. When circling another fish, these escalate to low grunts or thud sounds, thought to be a direct threat to the other fish. The piranha makes noises of different frequencies by contracting and relaxing muscles around the swim bladder, a gas-filled sac used to keep itself afloat. Finally, should its opponent refuse to back down, the piranha will gnash its teeth and give chase.
Piranhas gained notoriety as ferocious killers after US President Theodore Roosevelt wrote about a feeding frenzy he witnessed. Truth is, piranhas are primarily scavengers although they are opportunistic, and will prey on weak or small animals when available. During the incident, Amazonian natives staged a show for Roosevelt: piranhas were fenced up and starved for days, before being fed a cow carcass. Naturally, a feeding frenzy ensued!