Costs of thermoregulation in variable thermal environments in the jacky dragon ( Amphibolurus muricatus )

Thermoregulatory behaviour provides one of the main mechanisms by which animals compensate for fluctuations in environmental temperatures to maintain body temperatures within physiological optima. Thus, strategies of thermoregulation are predicted to be related to variation in environmental temperatures. We tested with jacky dragons ( Amphibolurus muricatus ) the prediction that the accuracy and effectiveness of thermoregulation would decrease as the costs of thermoregulation increase using experimental arenas to manipulate environmental temperature fluctuation. The results supported theoretical predictions on the costs of thermoregulation – environments that were fluctuating led to decreased accuracy of thermoregulation (increased deviations in body temperatures from preferred temperatures) and reduced thermoregulatory effort (effectiveness). Moreover, environments with a mean temperature farther from the preferred temperature also led to greater deviations in body temperature, although this had no significant effect on effectiveness of thermoregulation. Together, the results highlight the need to understand what influences the costs of thermoregulation (i.e. thermal variation and mean), and how great of costs will be accepted for the benefits associated with thermoregulation.