We used Takydromus septentrionalis as a model animal to examine whether lizards shift thermal preferences when fasted. The experiment was conducted in March 2007. Thirty-six adults collected from Shengsi, Zhoushan Islands, were equally assigned to experimental (fasted) and control (fed) groups, with nine housed together in a 0.6 m×0.2 m×0.5 m glass cage with moist soil (10 cm in depth), debris and grasses. A 100-W light bulb suspended above one end of each cage created a thermal gradient ranging from room temperatures (15℃-24℃) to 60℃ for 12 h daily, so that lizards could thermoregulate during the photophase. Prior to the experiment, lizards were allowed to feed on mealworms (larvae of Tenebrio molitor) for 10 days. Thereafter experimental lizards were fasted for 20 days, and were measured for thermal preferences on Day 1-10, Day 15 and Day 20 since fasting. We found in fasted lizards that selected body temperature (Tsel, a measure of thermal preference) gradually decreased from 32.4℃ to 30.9℃ in the first four days, and then increased to a level similar to that (32.9℃) recorded in the controls. Lizards fasted for 9 days or longer did not differ from controls in Tsel. Our study is the first to demonstrate that lizards fasted for a prolonged time may shift thermal preferences in a pattern well fitting to a Gaussian peak curve.
