Thermal preference and the effects of food availability on components of fitness in the bearded dragon, Pogona vitticeps

Abstract

Thermoregulatory indices are based on an estimation of the preferred body temperature range (Tset), but few studies have compared the different methods of measuring Tset or how these methods influence our understanding of the relationship between thermoregulation and physiological performance. For the bearded dragon, Pogona vitticeps, T sets were measured within a thermal gradient and shuttle box. Additionally, performance curves were determined for relative sprint speed and gut passage time. The shuttle box Tset was broader than the Tsets from the thermal gradient. Of the indices examines, only the effectiveness of thermoregulation may remain unaffected by differing methods of measuring Tset. The optimal Tbs for both performances were best described by the 50% Tb distribution. The Tb distributions were negatively skewed, suggesting support for net energy gain being maximized by thermoregulation. This study highlighted the need for more meaningful measures of thermoregulation than those provided only by temperature-dependent performances.