ENERGETICS AND WATER FLUX OF THE MARBLED VELVET GECKO (OEDURA-MARMORATA) IN TROPICAL AND TEMPERATE HABITATS

The gecko Oedura marmorata was studied in two different climatic zones : the arid zone of central Australia and ill the wet-dry tropics of no rthern Australia. Doubly labelled water was used to measure field meta bolic rate (FMR) and water Aux rates of animals in the field during th e temperate seasons of spring, summer and winter, and during the tropi cal wet and dry seasons. FMRs were highest in the tropical wet season and lowest in the temperate winter. The geckos in central Australia ex pended less energy than predicted for a similarly sized iguanid lizard , but geckos from the tropics expended about the same amount of energy as predicted for an iguanid. Water flux rates of geckos from the arid zone were extremely low in all seasons compared to other reptiles, an d although water flux was higher in tropical geckos, the rates were lo w compared to other tropical reptiles, The standard metabolic rates (S MRs) of geckos were similar between the two regions and among the seas ons. Geckos selected higher body temperatures (T(b)s) in a laboratory thermal gradient in the summer (33.5 degrees C) and wet (33.8 degrees C)seasons compared to the winter (31.7 degrees C) and dry (31.4 degree s C) seasons. The mean Tbs Selected in the laboratory thermal gradient by geckos from the two regions were not different at a given time of year, The energy expended during each season was partitioned into comp onents of resting metabolism, Tb and activity. Most of the energy expe nded by geckos from central Australia could be attributed to the effec ts of temperature on resting lizards in all three seasons. bur the ene rgy expended by tropical geckos includes a substantial component due t o activity during both seasons. This study revealed variability in pat terns of ecological energetics between populations of closely related geckos, differences which cannot be entirely attributed to seasonal or temperature effects.