Yawning and Its Temperature-Dependent Modulation in Leopard Geckos.

Yawning is a stereotyped behavior widely observed in vertebrates, serving as an adaptation to the environment. Previous research has highlighted the correlations between yawning and physiological arousal or temperature regulation. However, the majority of those studies have primarily focused on endothermic animals. Thus far, the function of yawning in ectothermic animals remains unclear. In this study, we observed the behavior of leopard geckos, Eublepharis macularius, ectothermic reptiles, over a period of 3 days under constant ambient temperatures of 25°C, 30°C, or 35°C. By investigating the relationship between temperature, spontaneous yawning, and activity levels, we found that yawning frequency is affected by ambient temperature, and also observed a significant increase in post-yawning activity particularly under the 30°C and 35°C conditions. Furthermore, a near 24-hour periodicity in yawning was detected under all temperature conditions. These results align with previous studies conducted on endothermic animals, suggesting the conservation of primitive functions of yawning across vertebrate species.