25.5 Sunday, Jan. 4 14:15 Target image expansion and contraction during visually-guided pursuit of prey induce jaw opening and closing by tiger beetles GILBERT, C*; PERKINS, M.Q.; ZUREK, D.B.; Cornell University; Cornell University; University of Pittsburgh email@example.com
In dynamic locomotory contexts, visual cues often trigger adaptive behavior by the viewer, yet studies investigating how animals determine impending collisions typically employ either stationary viewers or objects. Here we describe a dynamic situation of visually-guided prey pursuit in which both impending prey contact and escape elicit observable adaptive behaviors in the pursuer, a predatory tiger beetle. We investigated which visual cues independently control both opening and closing of the beetle’s jaws during chases of prey dummies. Jaw opening and closing typically occur when prey is within the 60° field of binocular vision, but not at a specific distance, angular size, expansion rate or time-to-collision. We show that a change in the sign of the expansion rate of the target image induces adaptive jaw movements. When the target image changes from contracting to expanding, indicating that the beetle is gaining on the target independent of the velocity of either, jaws open within about 15ms. When the image changes from expanding to contracting, indicating that the prey is getting away the jaws close after about 35ms. These values are close to the 28ms lag time we have recently determined for the beetle’s visual guidance system that controls whole body orientation during pursuit of prey. We discuss the “sloppiness” of the variation in the lag of the behavioral response, especially jaw closing, as an adaptation to uncertainty about target position due to degradation of the target image by motion blur from the fast running beetle.