Thermoregulation by the spotted tree monitor, Varanus scalaris, in the seasonal tropics of Australia

1. Varanus scalaris was studied in the wet and dry seasons by measuring body temperatures (Tb) in the field and in a laboratory thermal gradient, and by calculating operative temperatures (Te) in conjunction with microclimatic data.

2. In the field, predawn Tbs in the wet season were higher than in the dry season, and this is attributed to environmental conditions. Wet season Tbs were also higher during the day, but this is attributed to the behaviour of the lizards because Tes indicated that the thermal environment was not limiting. The mean midday Tb was 38.9°C in the wet season and 35.6°C in the dry.

3. In the laboratory, the lizards selected a mean Tb of 38.1°C in the wet season and 35.2°C in the dry season. Thus, in both the field and the laboratory, the lizards maintained Tbs approximately 3°C lower in the dry season.