title: Thermal ecology of the Australian agamid Pogona barbata.
abstract: This study compares the thermal ecology of male bearded dragon lizards (Pogona barbata) from south-east Queensland across two seasons: summer (1994-1995) and autumn (1995). Seasonal patterns of body temperature (Tb) were explored in terms of changes in the physical properties of the thermal environment and thermoregulatory effort. To quantify thermoregulatory effort, we compared behavioral and physiological variables recorded for observed lizards with those estimated for a thermoconforming lizard. The study lizards' field Tbs varied seasonally (summer: grand daily mean (GDM) 34.6 ± 0.6°C, autumn: GDM 27.5 ± 0.3°C) as did maximum and minimum available operative temperatures (summer: GDM Tmax42.1 ± 1.7°C, Tmin32.2 ± 1.0°C, autumn: GDM Tmax31.7 ± 1.2°C, Tmin26.4 ± 0.5°C). Interestingly, the range of temperatures that lizards selected in a gradient (selected range) did not change seasonally. However, P. barbata thermoregulated more extensively and more accurately in summer than in autumn; lizards generally displayed behaviors affecting heat load nonrandomly in summer and randomly in autumn, leading to the GDM of the mean deviations of lizards' field Tbs from their selected ranges being only 2.1 ± 0.5°C in summer, compared to 4.4 ± 0.5°C in autumn. This seasonal difference was not a consequence of different heat availability in the two seasons, because the seasonally available ranges of operative temperatures rarely precluded lizards from attaining field Tbs within their selected range, should that have been the goal. Rather, thermal microhabitat distribution and social behavior appear to have had an important influence on seasonal levels of thermoregulatory effort.
authors.affiliation: Department of Zoology, The University of Queensland, Brisbane, Queensland 4072, Australia Fax: 617 3365 1655; e-mail: cschauble@zoology.uq.edu.au, , , , , , AU.
authors.forename: Chloe S
authors.initials: CS
authors.lastname: Schäuble
authors.affiliation: Department of Zoology, The University of Queensland, Brisbane, Queensland 4072, Australia Fax: 617 3365 1655; e-mail: cschauble@zoology.uq.edu.au, , , , , , AU.
authors.forename: Gordon C
authors.initials: GC
authors.lastname: Grigg
keywords: Key wordsPogona barbata; Operative temperatures; Radiotelemetry; Selected range; Thermoregulation