Standard and maximal metabolic rates of goannas (Squamata:Varanidae)

Abstract

Standard metabolic rate and maximal metabolic rate during forced exercise are examined for nine species of goanna (genus Varanus), with body mass varying from 10 to 3,750 g. At 35 degrees C, the common pooled mass exponent for standard metabolic rate is 0.97 and at 25 degrees C it is 0.89, with considerable variation between species (0.43-1.20). Standard metabolic rate at 35 degrees C scales interspecifically with body mass0.92 and at 25 degrees C with body mass0.87. The Q10 for standard metabolic rate is approximately 2.5 between 25 degrees and 35 degrees C. At 35 degrees C, maximal metabolic rate scales intraspecifically with body mass0.79 and scales interspecifically with body mass0.72. Factorial metabolic scope ranges from nine for the larger species to 35 for the smaller species; it scales with body mass-0.199 at 35 degrees C. The maximal metabolic rate of 6.36 mL O2 g-1 h-1 for Varanus caudolineatus is the highest recorded for any squamate. Variations from the interspecific regression line appear to have some ecological significance. Varanus tristis (a widely foraging arboreal goanna) and Varanus eremius (a widely foraging terrestrial goanna) have a higher standard metabolic rate than Varanus acanthurus (a sedentary terrestrial goanna). The three arboreal goannas (Varanus caudolineatus, Varanus gilleni, and Varanus tristis) have a higher maximal metabolic rate than the terrestrial species (Varanus brevicauda, V. eremius, V. acanthurus, Varanus gouldii, Varanus rosenbergi, and Varanus panoptes).