Seasonal variation of behavioural thermoregulation in the Spotted Salamander (Ambystoma maculatum)

Mounting evidence suggests that temperature seasonality plays a pivotal role in shaping the thermal biology of ectotherms. However, we still have a limited understanding of how amphibians maintain thermal balance in the face of varying temperatures, especially in fossorial species. Due to thermal buffering underground, theory predicts relaxed selection pressure over thermoregulation in fossorial ectotherms. As a result, fossorial ectotherms typically show low thermoregulatory precision and low evidence of thermotactic behaviours when tested in laboratory thermal gradients. In this study, we evaluated how temperature selection (Tsel) and behavioural thermoregulation differed between seasons in the fossorial Spotted Salamander (Ambystoma maculatum). By comparing thermoregulatory parameters between the activity and overwintering seasons, we provide evidence that A. maculatum engages in active behavioural thermoregulation despite its fossorial habit. In both seasons, we found Tsel to be consistently offset higher than prevailing thermal conditions. Thermoregulation differed between seasons, with salamanders having higher Tsel and showing greater evidence of thermophilic behaviours in the active season compared to the overwintering season. Our study highlights that the combination of behavioural and thermal biology measurements is a necessary step to better understand the mechanisms that underlie body temperature control in amphibians. Ultimately, our study provides a broader understanding of thermoregulation in amphibians, particularly in the context of behavioural responses to seasonality in fossorial species. Summary statementBy comparing thermoregulatory parameters between seasons, we demonstrate that the Spotted Salamander engages in active behavioural thermoregulation despite being fossorial.