Maximum movement performance, not activity levels or thermoregulatory indices, affects survival in a free-ranging ectotherm

1. Temperature profoundly influences the distribution and diversity of ectotherms, yet in natural settings, the trade-offs between environmental temperatures, behaviour, physiological function, and how they drive individual survival, remain poorly understood. 2. To address these gaps, we generated field-based thermal performance curves, using temperature-sensitive radio transmitters and accelerometers, to examine the links between thermal biology and survival in a widely distributed, well-studied, lizard: the Australian central bearded dragon (Pogona vitticeps). Using this approach, we were able to link the accuracy and effectiveness of thermoregulation in the wild to address if seasonal trade-offs of thermoregulatory behaviours affect individual performance and ultimately test if thermal performance and thermoregulatory behaviours predict survival. 3. Lizards adjusted their behaviour to maintain optimal body temperature with higher thermoregulatory precision when environmental costs to maintain body temperature were low, during spring and summer, but decreased that precision during winter when the costs of active thermoregulation were high. 4. Maximum movement performance in the field was a strong predictor of individual survival, regardless of sex, even though survival probabilities were higher in males than females. Specifically, higher maximum movement performance increased predation and, as a result, mortality risk. Conversely, survival was not related to activity levels or thermoregulatory indices. 5. These findings highlight the complex trade-offs that ectotherms must navigate to balance behavioural thermoregulation and survival, emphasising the importance of seasonal and sex-specific differences in making those trade-offs. Connecting accelerometer data to energy expenditure and to specific behaviours is a promising avenue for research into thermal ecology. Such data provides critical insights into how ectotherms can respond to climate warming.