Rapid acceleration offsets the costs of intermittent locomotion in lizards when turning

Intermittent locomotion is a common locomotor mode in small vertebrates. Pausing is thought to aid in locating a predator or prey, enhanced crypsis, lowering energy costs, and/or maneuvering around obstacles or towards a refuge. Many lizards flee predators by turning as they pass a potential refuge and subsequently pause, presumably to conceal themselves. Intermittent locomotion may be associated with turning by allowing an animal time to assess its surroundings and/or decreasing the likelihood of losing its footing before or after turning. In this study, we quantify locomotor performance and the use of intermittent locomotion in Florida Scrub Lizards (Sceloporus woodi) when navigating either a 45° or 90° turn. Lizards paused in 92% of all trials, and yet despite pausing, linear speed was not different prior to entering or when exiting the turn. This result suggests that turning comes at minimal cost to forward speed for lizards under these conditions. The angle of the turn had no effect on whether lizards paused, nor was there a relationship with pausing before or after the turn. Interestingly, the speed in the turn did not differ in trials with a pause before the turn vs. trials without a pause. We found that lizards increase peak acceleration following pauses to achieve similar speed, and hence explain both why, and how, intermittent locomotion is such a common strategy in predator escape.

Methods
Data were collected by recording lizards running on 45 and 90 degree raceways while record above with high-speed video. Position data were digitized from lizards and a subset of trials retained to compare the frequency of pauses during trial and speed at various points during the trial. Position data were collected using DLTdv8 software, then analyzed in spreadsheets and using JMP analysis software.