Studies on the environmental physiology of some Australian lizards from arid and semi-arid habitats.

Abstract

The microclimate of an arid habitat was studied at midsummer. Several species of lizards found there, and in semi-arid habitats, were examined. The lizards were: Agamidae; Amphibolurus reticulatus inermis (De Vis), A pictus Peters, A. cristatus Gray, and A. decresii Dumeril & Bibron; Varanidae, Varanus gouldii Gray; Scincidae, Tiliqua melanops Stirling & Ziets. The rate of water loss by evaporation was determined under different combinations of temperature and humidity. Of the lizards studied, A. r. inermis was the only species fully adapted to life in arid conditions. No evidence for evaporative cooling of the body at high temperatures was obtained. It is suggested that this lizard survives in arid habitats mainly because it is able to tolerate long exposures to high temperatures and low humidities, not because it is capable of maintaining low temperatures. The rate at which water is lost by this lizard was remarkably low when compared with the other lizards. The curves of increasing water loss in dry air at 37.5°C (in agamids) may be indicative of their degree of adaptedness. Thus, A. r. inermis has the lowest rate of water loss, followed by A. pictus, A. cristatus, and A. decresii, respectively. The skink, T. melanops, and the goanna, V. gouldii, show a fairly low rate of evaporation at that temperature.