Thermoregulatory and thermal dependence of resting metabolic rates in the Chinese crocodile lizard Shinisaurus crocodilurus in the Luokeng Nature Reserve, Guangdong

To explore the thermoregulatory and thermal dependence of resting metabolic rates (RMR) in the Chinese crocodile lizard Shinisaurus crocodilurus, we measured the active body temperature, the diel variation in body temperature, the average daily body temperatures, the ambient temperature and the resting metabolic rate in the wild and under controlled laboratory conditions. Results showed that in the wild, active body temperature (Tb) was higher than substrate temperature (Tc) and air temperature (Td) and was positively correlated with the latter two (Tb = 11.65 + 0.47Tc , r2 = 0.34, F1, 75= 39.11, P < 0.0001; Tb = 11.61 + 0.46Td, r2 = 0.56, F1, 75= 96.56, P < 0.0001). The active body temperature of the lizard in the wild showed monthly variations, and no effect of age or sex. In the laboratory in a gradient of 15℃–30℃, the resting body temperature (Tb) was positively correlated with ambient temperature (Ta): Tb = 12.450 + 0.5641 Ta (F1, 110=11.34, r2 = 0.997, P < 0.001). In the environment without thermal gradients, there was a significant diel variation in body temperature, air temperature and substrate temperature, but there were no significant differences in average daily body temperature, air temperature and substrate temperature. The RMR showed no difference between sexes, and it increased with ambient temperature (Ta). Further analysis indicated that the thermoregulation of Chinese crocodile lizard was conducted by both behavioral and physiological means, and both thermoregulation and the resting metabolic rates of Chinese crocodile lizard were in accordance with the thermal biology of this ectothermic species. The capability of physiological thermoregulation of Chinese crocodile lizard was relatively higher than that of other more active lizards. The thermoregulation of Chinese crocodile lizard parallels its behavioral characteristics of spending most of their time at rest [Acta Zoologica Sinica 54（6）：964–971, 2008].