A global analysis of field body temperatures of active squamates in relation to climate and behaviour
Authors: Dubiner Shahar , Aguilar Rocío , Anderson Rodolfo O. , Arenas Moreno Diego M. , Avila Luciano J. , Boada‐Viteri Estefania , Castillo Martin , Chapple David G. , Chukwuka Christian O. , Cree Alison , Cruz Félix B. , Colli Guarino R. , Das Indraneil , Delaugerre Michel‐Jean , Du Wei‐Guo , Dyugmedzhiev Angel , Doan Tiffany M. , Escudero Paula , Farquhar Jules , Gainsbury Alison M. , Gray Brian S. , Grimm‐Seyfarth Annegret , Hare Kelly M. , Henle Klaus , Ibargüengoytía Nora , Itescu Yuval , Jamison Simon , Jimenez‐Robles Octavio , Labra Antonieta , Laspiur Alejandro , Liang Tao , Ludgate Jackie L. , Luiselli Luca , Martín José , Matthews Genevieve , Medina Marlin , Méndez‐de‐la‐Cruz Fausto R. , Miles Donald B. , Mills Nathan E. , Miranda‐Calle Alejandro Bruno , Monks Joanne M. , Morando Mariana , Moreno Azocar Débora L. , Murali Gopal , Pafilis Panayotis , Pérez‐Cembranos Ana , Pérez‐Mellado Valentín , Peters Richard , Pizzatto Ligia , Pincheira‐Donoso Daniel , Plummer Michael V. , Schwarz Rachel , Shermeister Ben , Shine Richard , Theisinger Ole , Theisinger Wiebke , Tolley Krystal A. , Torres‐Carvajal Omar , Valdecantos Soledad , Van Damme Raoul , Vitt Laurie J. , Wapstra Erik , While Geoffrey M. , Levin Eran , Meiri Shai 
Published: January 2024

Aim

Squamate fitness is affected by body temperature, which in turn is influenced by environmental temperatures and, in many species, by exposure to solar radiation. The biophysical drivers of body temperature have been widely studied, but we lack an integrative synthesis of actual body temperatures experienced in the field, and their relationships to environmental temperatures, across phylogeny, behaviour and climate.

Location

Global (25 countries on six continents).

Taxa

Squamates (210 species, representing 25 families).

Methods

We measured the body temperatures of 20,231 individuals of squamates in the field while they were active. We examined how body temperatures vary with substrate and air temperatures across taxa, climates and behaviours (basking and diel activity).

Results

Heliothermic lizards had the highest body temperatures. Their body temperatures were the most weakly correlated with substrate and air temperatures. Body temperatures of non‐heliothermic diurnal lizards were similar to heliotherms in relation to air temperature, but similar to nocturnal species in relation to substrate temperatures. The correlation of body temperature with air and substrate temperatures was stronger in diurnal snakes and non‐heliothermic lizards than in heliotherms. Body‐substrate and body‐air temperature correlations varied with mean annual temperatures in all diurnal squamates, especially in heliotherms. Thermal relations vary with behaviour (heliothermy, nocturnality) in cold climates but converge towards the same relation in warm climates. Non‐heliotherms and nocturnal species body temperatures are better explained by substrate temperature than by air temperature. Body temperature distributions become left‐skewed in warmer‐bodied species, especially in colder climates.

Main Conclusions

Squamate body temperatures, their frequency distributions and their relation to environmental temperature, are globally influenced by behavioural and climatic factors. For all temperatures and climates, heliothermic species' body temperatures are consistently higher and more stable than in other species, but in regions with warmer climate these differences become less pronounced. A comparable variation was found in non‐heliotherms, but in not nocturnal species whose body temperatures were similar to air and substrate irrespective of the macroclimatic context.