Meeting Abstract
Flying snakes exhibit numerous behaviors that suggest that they actively control their gliding locomotion. Flying snakes are also characterized by large eyes relative to head size, and a large optic tecum, relative to brain volume. This evidence suggests vision may be a valuable sensory modality, which may be employed to estimate timing and distance of jumps and in-air turns, and to inform landing site choices. However, the performance limits of their sensory systems have not been characterized. Here we ask: what are the spatial and temporal limits of vision in flying snakes? What behaviors are elicited when these snakes are presented visual motion? To investigate these questions, we placed Chrysopelea ornata and C. paradisi in an optomotor drum and presented a vertical black-and-white grating of varying spatial densities (1.7 – 125 cycles per degree) that rotated at varying speeds (3-48 deg/s) with constant luminance. Using tracked head position, we calculated behavioral kinematics, including head direction, angular rotation, and head displacement. We found that freely moving snakes present a series of behaviors including nystagmus (smooth pursuit and snap back), head-tracking (smooth pursuit only), head wagging (lateral oscillatory translations), targeting (fast approach to a single dark bar), chasing (moving with the stimulus around the drum), and climbing. Based on preliminary data, the ratios of these behaviors change with stimulus speed. Both species are capable of head-tracking a stimulus up to about 2.1 cpd, and were observed chasing stimuli rotating at 48 deg/s, producing the equivalent flicker speed of about 99 Hz. These data suggest that flying snakes possess spatial acuity and visual processing speeds that could be advantageous for landing site selection and in-air control.
