Ectotherms are known to function optimally within a specific range of body temperatures, bordered by two setpoint values (i.e. preferred temperature range; T-p). Preferred body temperature stands central in understanding behavioural thermoregulation in a thermally dynamic temperate environment. In this study we determined T-p for the group-living cordylid lizard, Ouroborus cataphractus, during the respective annual peak periods in food availability and scarcity. Body temperatures were recorded in ecologically realistic photo-thermal gradients using body-mounted, modified iButtons. In addition to studying seasonal and spatial variation in T-p we also assessed daily variation and among-day repeatability of T-p estimates. The mean T-p among populations and across seasons was 29.8 +/- 2.3 degrees C (range: 26.8-32.6 degrees C) and represents the lowest mean T-p and range recorded for any cordylid lizard to date. Literature reports on the seasonal activity patterns and micro-spatial variation in thermal habitat quality of O. cataphractus suggest that the low T-p minimizes thermoregulatory costs during summer, autumn, late winter and spring. The low T-p is therefore expected to relax energy budgets and function as part of the adaptive strategy of the species to survive seasonal food stress in a semi-arid environment. The among-day repeatability of mean T-p varied among populations and across seasons despite exposure conditions that were kept constant. The results of the present study suggest that T-p estimates based on short term laboratory trials may be inaccurate due to potential high among-day individual variation and low repeatability in thermal preference.
