Environmental conditions and body temperature of anurans in mountain regions of the Atlantic Forest, Brazil

Introduction Mountainous tropical regions are characterized by complex microclimatic heterogeneity, which exerts strong selective pressure on the thermal biology of ectotherms. Understanding how environmental conditions, organismal traits, and habitat use shape thermal responses is essential for predicting species vulnerability under climate change. Methods We evaluated the environmental, morphological, and demographic drivers of body temperature (T b ) in 16 anuran species (n = 146) along an elevational gradient (980–2,600 m) in the Brazilian Atlantic Forest. We measured T b non-invasively using infrared thermometry and recorded air (T a ) and substrate (T s ) temperatures, morphological traits, sex, elevation, and microhabitat type. We used linear mixed-effects models, with species identity as a random effect, to assess predictors of T b , and compared thermal variation between diurnal and nocturnal species. Results Body temperature ranged from 12.2 to 22.1 °C. The only diurnal species, Melanophryniscus moreirae , exhibited greater intraspecific thermal variation than the nocturnal assemblage. Substrate temperature and microhabitat type were the main predictors of Tb, whereas Ta, body size, body mass, and sex showed no significant effects. Discussion Our findings suggest that habitat degradation that reduces thermal buffering, combined with projected nocturnal warming, may increase the vulnerability of thermally constrained nocturnal species. Integrating physiological data with diel niche dynamics is therefore critical for predicting climate change impacts and guiding conservation strategies.