SENSORY MODULATION AND BEHAVIORAL CHOICE DURING FEEDING IN THE AUSTRALIAN FROG, CYCLORANA-NOVAEHOLLANDIAE

This study investigates how visual and tactile sensory information, as well as biomechanical effects due to differences in physical characte ristics of the prey, influence feeding behavior in the frog Cyclorana novaehollandiae. Video motion analysis was used to quantify movement p atterns produced when feeding on five prey types (termites, waxworms, crickets, mice and earthworms). Twelve kinematic variables differed si gnificantly among prey types, and twelve variables were correlated wit h prey characteristics (including mass, length, height and velocity of movement). Results indicate that C. novaehollandiae uses a different strategy to capture each prey type. Visual assessment of prey characte ristics appeared to be more important in modulating feeding behavior t han tactile cues or biomechanical effects. We propose a hierarchical h ypothesis of behavioral choice, in which decisions are based primarily on visual analysis of prey characteristics. In this model, the frogs first choose between jaw prehension and tongue prehension based on pre y size. If they have chosen jaw prehension, they next choose between u pward or downward head rotation based on length and height of the prey . If they have chosen tongue prehension, they next choose between beha vior for fast and slow prey. Final decisions may be the result of beha vioral fine tuning based on tactile feedback.