Effects of constant and fluctuating incubation temperatures on hatchling traits in Salvator merianae: an integrative...

In egg-laying reptiles, incubation temperature significantly influences numerous hatchling characteristics, including growth rate, morphology, locomotor performance, behavior, and immune system development, all of which impact survival. Climate-induced thermal stress, wildfires, and habitat fragmentation are threats to reptile populations by disrupting suitable nesting sites and optimal incubation temperatures, thereby impacting hatching success and the performance of hatchlings. This study explores how constant (29 °C and 32 °C) and fluctuating (25-35 °C) incubation temperatures affect hatching success, developmental timelines, morphology, and locomotion in Salvator merianae in Santa Fe, Argentina. In their natural habitat, the choice of nesting sites by female Salvator merianae is critical for maintaining constant temperature conditions for embryo development, minimizing temperature fluctuations. The study revealed that higher or variable temperatures accelerated development and enhanced sprint speed but reduced hatching success and hatchling size compared to those from the constant regime. These results show that moderate, stable thermal environments optimize embryonic survival, whereas increased temperature or thermal variability may enhance performance-related traits, reflecting a trade-off between developmental rate and viability. This research underscores the importance of preserving habitats to ensure the availability of nest sites that can buffer environmental extremes and promote suitable conditions for embryonic development. Understanding how thermal conditions influence functional traits and early survival is essential for predicting biological responses under climate change scenarios and informing conservation strategies for oviparous reptiles.