Author ORCID Identifier
Document Type
Dissertation
Date of Award
2026
Degree Name
Doctor of Philosophy (PhD)
Department
Biology
First Advisor
Christopher V Anderson
Abstract
Chameleons are well known for their highly specialized feeding mechanism, which allows them to ballistically project the tongue at high performance to catch prey up to 2.5 body-lengths away. The extreme performance and degree of specialization of this system might suggest that chameleons are limited to feeding only via tongue projection. However, some species have been documented approaching and directly grabbing food items using only their jaws. The underlying mechanisms of this feeding strategy, and its evolutionary and ecological significance, have never been examined. I investigate jaw prehension in chameleons to determine its relationship to ballistic tongue projection, its variation across species, and its evolutionary origins. Specifically, I test whether jaw prehension represents a similar strategy to the ancestral jaw-based feeding in basal lizard lineages, or whether it is more similar to the specialized ballistic tongue projection in chameleons, which can be modified for use in specific ecological contexts, such as prey type or thermal condition. Using high-speed videography and electromyography, I compare kinematics and muscle activity patterns during tongue projection and jaw prehension in two chameleon species and a closely related agamid. These analyses reveal that jaw prehension occurs through selective adjustments of individual muscle activities rather than a complete restructuring of the feeding system. Tongue projection is highly conserved across chameleons, whereas jaw prehension exhibits substantial divergences among species and families, highlighting its relative flexibility and adaptive potential. Furthermore, jaw prehension appears to be largely driven by prey type. Chameleons utilize this feeding strategy on slow or nonmobile food items and strategy choice remains consistent across temperatures, indicating that chameleons do not shift to thermally robust elastic-powered tongue projection when lower temperatures reduce muscle performance. Altogether, these findings challenge the view that extreme specialization limits behavioral flexibility. Even highly specialized systems can possess alternative functional capacities through modification of neuromuscular control rather than changes in morphology. Organisms can evolve novel behaviors by modifying timing and coordination of existing systems. In chameleons, the combination of specialized ballistic tongue projection and the capacity for jaw prehension illustrates how specialized systems can retain functional flexibility, allowing access to novel ecological opportunities.
Subject Categories
Biology
Keywords
Chamaeleonidae, Electromyography, Feeding Performance, Jaw Prehension, Temperature Effects
Number of Pages
111
Publisher
University of South Dakota
Recommended Citation
Schneider, Nikole, "Mechanisms and evolution of a novel feeding strategy in chameleons" (2026). Dissertations and Theses. 420.
https://red.library.usd.edu/diss-thesis/420