|Acontias percivali, JCM|
Limblessness has evolved numerous times in squamates and as it does it limits the animal’s abilities in a variety of ways. Limbless lizard species are usually grass or litter swimmers or they burrow. Burrowing head first may limit the head size, and therefore limit the bite force of the animal. The consequences of this may be more important to males that compete for mates using combat. Burrowing rapidly may be important in escaping a predator, but it means a narrower head and loss of bite force. Bieke Vanhooydonck and colleagues have investigated how loss of legs affects the ability to burrow using the legless African skink Acontias percivali (Scincidae, Acontiinae). They used an ingenious device to measure burrowing force that positioned the lizard in a plastic tunnel so that it would push its head into soil in a box mounted on a force plate. They measured bite force using an isometric Kistler force transducer. Their results suggest that A. percivali uses a burrowing style that involves the skink’s entire body to generate force, peak force was generated by total length. They also found both bite force and the time needed to burrow into the substrate were determined by relative head width, suggesting a trade-off between biting and burrow speed. Performance data were indeed suggestive of a correlation between bite force and the time needed to burrow, but additional data are needed to confirm this pattern. Trade-offs apparently do occur and may have been important in shaping the head during the evolution of A. percivali, and other burrowing species.
Vanhooydonck, B., R, Boistel, V. Fernandez, A. Herrel. 2011. Push and bite: trade-offs between burrowing and biting in a burrowing skink (Acontias percivali). Biological Journal of the Linnean Society 102:91–99.