Meeting Abstract
Tongue-flicking in lizards and snakes is used primarily for chemo- and mechanosensation. This behavior is characterized by sweeping, vertical movements of the tongue, with variations that include single bouts or high-frequency oscillations that occur multiple times per second. In previous studies of flying snakes (genus Chrysopelea), we observed what appeared to be tongue protrusion without oscillatory flicking, occurring only in the context of locomotion. To investigate this behavior, we studied tongue movements of Chrysopelea paradisi during locomotion with a setup designed for gap crossing. This setup consisted of two artificial branches oriented horizontally and suspended 1.5 m above the ground, with a gap of about 21 cm. Two high-speed cameras (Photron APX-RS) were used to record tongue behavior at 200 fps, while a synchronized motion capture system (Vicon) recorded the three-dimensional position of the head. Snakes often exhibited tongue protrusion without vertical movement, a behavior that we term as a ‘tongue-stick’. Specifically, the snake protruded the tongue after entering the gap, and retracted it just prior to reaching the target branch. In between, the tongue remained extended in a static posture as snake translated forward. We also recorded snakes slithering prior to entering the gap, and as a control, across the branches but with the gap closed. Tongue-sticking occurred in both conditions, indicating that this behavior is not restricted to gap crossing. In contrast, tongue-sticking was not observed when snakes were at rest, congruent with informal observations in their lab habitat enclosures. The function of tongue-sticking is unclear, but its association with locomotion suggests a possible non-chemosensory role.
