Out of the fire and into the frying pan: Hostile post‐fire thermal conditions reduce activity windows for reptiles

Abstract Climate change and intensified fire regimes are reshaping ecosystems globally. Reptiles, as ectotherms, rely on microhabitat shelters to buffer against thermal extremes, yet the capacity of these shelters to persist or function following fire remains poorly understood. As heatwaves and fire regimes intensify under climate change, effective thermal buffering will become increasingly vital for reptile persistence. This study quantifies how fire alters the structure and thermal offset of key reptile refugia: spinifex ( Triodia ) tussocks, chenopod shrubs, and leaf‐litter mats, in the dune and swale habitats of South Australia's Murray Mallee. Using iButton data loggers deployed across four fire histories, we measured hourly microhabitat and adjacent ground temperatures, modelling thermal offset (T offset ) via mixed‐effects models. More recent fire histories were associated with less spinifex and leaf‐litter cover and more bare ground, although evidence for changes in individual shelter dimensions was mixed. Thermal buffering declined markedly in recently burnt sites, with long‐unburnt spinifex providing the greatest daytime protection from extreme ground temperatures. Structural properties such as tussock height and litter depth were associated with T offset , supporting a relationship between shelter structure and thermal‐refuge quality. Comparisons with the thermal tolerance of spinifex‐obligate reptiles indicate that burnt habitats often exceed critical thermal limits, effectively eliminating usable refugia during heatwaves. These results demonstrate that fire‐driven structural simplification translates to weakened thermal refugia, with implications for species persistence under increasing heat extremes. Effective fire management in arid systems should, therefore, prioritise the protection and regeneration of long‐unburnt spinifex and litter habitats as critical microclimatic refuges. Read the free Plain Language Summary for this article on the Journal blog.