How to Survive a (Juvenile) Piranha Attack: An Integrative Approach to Evaluating Predator Performance.

FIGURES

Cory cat panel figureDrawing of bite force measuring equipment and indentation rig jaw muscle morphology and skull anatomyBox plot grid of number of bites before puncture along different body regions of during feeding trials resultsDrawing of color-coded with attack frequencies and average bites until puncture by Box plot of average voluntary juvenile bite forces to standard lengthPanel of linear ordinary least-squares regressions of bite force to adductor mandibulae mass, standard length, and body massOrdinary least-squares regressions of voluntary bites to restrained bites of Panel of indentation tests for intact and removed scutesPanel of indentation tests for body region.

SYNOPSIS

There is an evolutionary arms race between predators and prey. In aquatic environments, predatory fishes often use sharp teeth, powerful bites, and/or streamlined bodies to help capture their prey quickly and efficiently. Conversely, prey are often equipped with antipredator adaptations including: scaly armor, sharp spines, and/or toxic secretions. This study focused on the predator-prey interactions between the armored threestripe cory catfish () and juvenile red-bellied piranha (). Specifically, we investigated how resistant cory catfish armor is to a range of natural and theoretical piranha bite forces and how often this protection translated to survival from predator attacks by . We measured the bite force and jaw functional morphology of , the puncture resistance of defensive scutes in , and the predatory interactions between the two. The adductor mandibulae muscle in juvenile is robust and delivers an average bite force of 1.03 N and maximum bite force of 9.71 N, yet its prey, , survived 37% of confirmed bites without any damage. The armor withstood an average of nine bites before puncture by . Predation was successful only when piranhas bit unarmored areas of the body, at the opercular opening and at the caudal peduncle. This study used an integrative approach to understand the outcomes of predator-prey interactions by evaluating the link between morphology and feeding behavior. We found that juvenile rarely used a maximal bite force and displayed a net predation success rate on par with other adult vertebrates. Conversely, successfully avoided predation by orienting predator attacks toward their resilient, axial armor and behavioral strategies that reduced the predator's ability to bite in less armored regions of the body.