Kinematics of the Chameleon Feeding Mechanism through Ontogeny



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Chameleons are sit-and-wait predators and employ a unique feeding mechanism that enables them to capture prey from great distances. This feeding mechanism is complex and requires that an extraordinary number of structures and events be precisely coordinated and powerfully executed. Due to the intricacy of the mechanism, it is likely that body size affects its kinematics. To investigate this I video-recorded feeding sessions with four chameleons (Chamaeleo calyptratus) throughout their growth from 1.63 to 58 g. Results indicate a general slowing in timing of events and a decrease in maximum velocities (average 33.1 m/s) and accelerations (average 420 m/s2) of the tongue tip. Average gape distance at prey contact increased with body size while gape angle at prey contact remained nearly constant. Also, because chameleons are arboreal generalist predators, they must be able to capture numerous types of prey at many positions relative to their head. Hence I was also interested in looking at the effects of prey size and position on kinematics. In general, both increasing prey size and distance to the prey item caused an increase in maximum velocity of the tongue. Angular position relative to the chameleon s head did not have a significant effect on feeding kinematics.



chameleon feeding, biomechanics, ontogeny