Chameleons have developed a highly specialized form of tongue prehension to capture prey from long distances. An elastic recoil mechanism is used to ballistically project the tongue out of the mouth, contact a prey item, and return it to the mouth. Though ballistic tongue projection is the typical method of prey capture, certain chameleon species have been documented eating specific prey items, such as gastropods, by directly capturing them using their jaws. This method of prey capture has only been described at a very basic level and the underlying mechanisms have never been examined in a comparative context to their normal feeding method. I will compare the kinematics and motor control patterns of chameleons while feeding by (1) ballistic tongue projection and (2) direct prey capture to evaluate whether these feeding strategies are constrained to the same specialized motor control patterns, or if evolving to feed via direct prey capture also necessitated the evolution of a novel feeding motor control pattern. I predict that certain aspects of the motor control and kinematics of chameleon feeding are constrained, whether feeding by traditional ballistic tongue projection or by direct prey capture. I also predict that motor control patterns will remain similar during both feeding strategies, but direct prey capture will exhibit a shorter or reduced feeding pattern. Examining the kinematics and motor control patterns of these strategies using high-speed video and electromyographic (EMG) recordings will shed light on the evolutionary consequences of highly specialized mechanisms like the chameleon tongue evolving novel feeding strategies. Furthermore, this novel method of prey capture in chameleons is used by invasive chameleon populations in Hawaii to feed on Critically Endangered endemic snail species. Increased knowledge of these predatory feeding strategies will help contribute to conservation management or protection strategies of endemic species threatened with extinction.
Christopher V. Anderson
Schneider, Nikole, "Kinematics and neuromotor control patterns of a novel feeding mechanism in chameleons" (2021). IdeaFest. 411.