Piranha predators include Amazon river dolphins, herons, and crocodile-like yacare caimans. The fish generally range in size from 8 to 12 inches and rarely exceed 2 feet. They have stout, narrow bodies, sharp bellies, blunt heads and, of course, razor-sharp teeth. Despite the teeth, most piranha species are scavengers and some are even vegetarians. They have a preference for prey smaller or slightly larger than themselves.
Bellono Lab’s work centers on feeding, specifically feeding frenzies, which is when fish converge on an injured animal and, well, feast. A frenzy involving hundreds of piranhas can reduce prey to bone in minutes.
Caribbean piranhas are believed to be more aggressive than their red-bellied counterparts. Kilian wants definitive proof. In experiments, he will look closely at how quickly fish eat their prey, how many are involved in an attack, and how closely they group together before making their first strike.
Piranhas are fed a fatty, protein-rich fish called capelin. For regular meals, researchers cut frozen fish into small pieces and throw them in the tank. When doing behavioral experiments, they thaw the whole fish and hang it in the tank. Then they watch.
The piranha usually starts with a few bites, targeting the eyes and tail to immobilize the capelin if it were in the wild. It all looks quite orderly and calm, if the piranhas are well fed. When they are hungry, it quickly becomes a frenzy.
“What I’m interested in is if this group feeding is happening because of social signals between different fish or if there’s some kind of chemical signaling between fish that’s causing it or if it’s just the result of their hunger,” Kilian said. mentioned. “We’re hoping to be able to do some type of computer-assisted tracking of fish to really understand the subtle differences in frenzy behavior.”
Besides the fact that she and Kilian are both animal lovers, this type of project rewards the full-time effort managing the logistics and animal care behind the science, Walsh said.
“I’ve often thought of putting a sign in the back of my car: something like ‘Please don’t chase me, I have water splashing out the back’ or ‘Fish at edge”.