Metabolism and evaporative water loss of Western Australian geckos (Reptilia : Sauria : Gekkonomorpha)

Abstract

Resting metabolic rate (RMR) and evaporative water loss (EWL) were measured, and resistance (R) to evaporative water loss and water use index (WUI = EWL/RMR) were calculated, for 22 species of Western Australian gecko. For all available gecko data, body mass and temperature explained 85% of the variability in RMR (=14.5 mass^0.833 10^{0.0398 Ta} µL h^–1), and 70% of the variability in EWL (=0.126 mass^0.539 10^{0.049 Ta} mg h^–1 ). For Western Australian geckos, RMR and EWL were significantly influenced by body mass, using conventional regression and phylogenetic analyses. Resistance to evaporative water loss (R) was not significantly affected by body mass. Water use index was inversely related to body mass: WUI = 21.9 M^–0.344 mg mL O₂^–1. There were significant differences between species for R and for standardised residuals of RMR, EWL and WUI. R was not correlated with phylogeny, and was significantly higher (P = 0.020) for saxicolous geckos (1467 s cm^-1) than terrestrial geckos (797 s cm^–1); arboreal geckos had an intermediate R (977 s cm^–1). Species that ate termites had lower standardised linear regression residuals (P = 0.003) for RMR than did species that ate more general diets. Standardised residuals for EWL were almost significantly related to microhabitat (P = 0.053). Standardised residuals for WUI were significantly related to microhabitat (P = 0.016); saxicolous species had lower WUI than terrestrial species. Standardised linear regression residuals of the residuals from autoregression (which should be independent of both mass and phylogeny effects) still significantly correlated RMR and diet, but not EWL or WUI with microhabitat.