EIDIETIS, Laura: Escape response of Rana sylvatica and Rana clamitans tadpoles

Predation of dragonfly larvae (Anax junius) on wood frog (Rana sylvatica) tadpoles was observed using standard and high-speed video. Typical predatory behavior of A.junius consists of stalking, extending the lower mouthparts, grasping the tadpole, and drawing it into the mouth. A. junius typically neither chase prey nor repeat strikes before tadpoles move out of range. R. sylvatica response to A. junius contact begins with curling into a tear-drop shape, followed by large-amplitude tail motions. Both curl and tail motions often rip R. sylvatica from the grasp of A. junius , at which point, the tail motions propel the tadpole. Green frog (Rana clamitans) tadpole response to poking were recorded and analyzed to ascertain whether tadpole escape behavior is caused by touch and to acquire multiple replicates of the response for analysis of kinematics. R. clamitans response to poking was similar to R. sylvatica response to A. junius strikes. The curl consisted of rotating the body around the center of mass while folding the tail towards the body. The amplitude of tail motions increased linearly with distance from the center of mass. A probabilistic model based on these descriptions of predation and escape behavior predicts that the performance of both the curl and the tail motions affects the probability of tadpoles surviving A. junius strikes. Increasing the rotational momentum of the point of contact would improve curl and tail motion performance. An empirically based model suggests that morphological changes induced by predators in R. sylvatica would serve to substantially increase the curl and tail motion performance, thereby increasing the probability of surviving a predatory strike.