Energy and Water Turnover in Two Tropical Varanid Lizards, Varanus bengalensis and V. salvator

Abstract

Water influx rates and CO2 production were determined in the field for two large sympatric lizards, Varanus bengalensis and V. salvator, with mean body masses of 2.56 and 7.60 kg, respectively. The two species exhibited similar water influx rates (60.5 and 54.5 ml kg-' day-', respectively) and metabolic rates (0.249 and 0.195 ml CO2 g-I hr-1, respectively) despite major differences in their behavior and thermal profiles. Varanus bengalensis is terrestrial and maintains high diurnal body temperatures but, by retreating to cool refugia, lowers body temperature overnight. Varanus salvator is predominantly aquatic and maintains a body temperature of about 30 C by day and night. The water fluxes and metabolic rates of both species are substantially higher than in varanids from semiarid and arid habitats, and are higher than predicted for other tropical reptiles. Approximately 60% of water influx is derived from drinking and pulmocutaneous exchange in both species.