SOLAR ABSORPTANCE OF SOME AUSTRALIAN LIZARDS AND ITS RELATIONSHIP TO TEMPERATURE

The absorptance to solar radiation, integrated across a wide range of wavelengths, was measured for selected species of Australian lizards. Some, but not all, agamids demonstrated the ability to change absorpta nce. None of the varanid lizards measured changed absorptance, includi ng Varanus storri, which had been reported to change colour. An energy balance model was used to explore the effects of absorptance, changes in absorptance, and body size in varanid lizards, the dragon Ctenopho rus caudicinctus (which changed absorptance from 77.0 to 87.7%) and th e frillneck lizard (Chlamydosaurus kingii). Although higher absorptanc e values generally result in higher body temperatures, the effect of b ody size is great and must be taken into account in comparisons. Altho ugh some species with high absorptances are associated with relatively cool climates (Varanus rosenbergi) or with a semi-aquatic lifestyle ( V. mertensi), the absorptances of other species are not as easily expl ained [such as the high absorptances of the tropical terrestrial V. pa noptes (87%) and the tropical arboreal V. scalaris (86%)]. The absorpt ances of more species are required before the importance of climate an d phylogenetic relationships can be fully evaluated. To facilitate fut ure measurements, the apparatus used in this study is described in det ail.