The Effect of Temperature and Thermal Acclimation on Locomotor Performance in Xantusia vigilis, the Desert Night Lizard

The influence of body temperature (12.5°-37° C) and thermal acclimation (20° and 30° C) on sprint speed in a thigmothermic lizard, Xantusia vigilis, was measured. Body temperature has a profound influence on sprint speed, which is maximal at 33°-34° C and declines exponentially at lower body temperatures. Neither sprint speed nor its thermal dependence was modified by thermal acclimation over the body temperature range of 15.0°-34° C. In contrast, acclimation temperature did affect sprint speed at more extreme temperatures: 20° C-acclimated lizards ran faster at 12.5° and slower at 37°C than did 30°C-acclimated animals. Acclimation also affected preferred body temperatures and critical thermal minima and maxima: all were significantly lower in the 20°C-acclimated group (31.1°, 4.5°, and 40.5°C, respectively) than in the 30°C-acclimated group (33.0°, 9.4°, 43.0°). Ac-climation may therefore shift critical thermal variables without affecting locomotor performance at intermediate temperatures.