Beneath the surface: physiology, behaviour, and performance of fossorial amphibians and reptiles

Danilo Giacometti , Melissa Bars-Closel, José Eduardo de Carvalho, Glenn J Tattersall

Fossoriality has evolved recurrently in amphibians and reptiles, exposing organisms to a distinctive physical environment that has favoured diverse morphological, physiological, behavioural, and biomechanical adaptations to enable life beneath the surface. Despite substantial progress over recent decades, research has largely examined these traits independently, limiting our understanding of how fossorial ectotherms function as integrated organisms. Here, we synthesise current knowledge on the mechanisms underlying fossoriality in amphibians and reptiles, focusing on the interactions among morphology, functional performance, thermoregulation, water balance, respiration, energetics, and seasonal dormancy. We show that physiological and behavioural responses reflect continuous trade-offs among temperature, water availability, respiratory gases, and substrate properties, highlighting the multidimensional nature of the subterranean environment. Likewise, many features commonly associated with fossoriality, including body elongation, limb reduction, cranial reinforcement, and sensory reorganisation, have evolved repeatedly but through lineage-specific combinations of traits rather than a single adaptive syndrome. We argue that understanding fossoriality requires moving beyond descriptive accounts of individual traits towards an integrative framework that connects organismal function with environmental conditions. We identify key knowledge gaps and propose future research priorities centred on comparative studies, experimental approaches that manipulate multiple environmental variables simultaneously, and the integration of empirical data with mechanistic biophysical models. Together, these approaches offer a predictive framework for understanding how fossorial amphibians and reptiles interact with heterogeneous subterranean environments and provide a foundation for a more mechanistic understanding of one of the most remarkable lifestyles among terrestrial vertebrates.