Infrared thermography is a useful tool in research on thermoregulation and evolution of heat tolerance

Non-invasive methods for measuring thermal tolerance and thermoregulation in large numbers of individuals under natural environmental conditions are useful to understand the capacity of species to adapt to future climate scenarios. Infrared thermography (IRT) is one such tool in research on thermal adaptation, but concerns have been raised about its reliability, specifically the correlation between surface temperature (<i>T</i> _s) and body temperature (<i>T</i> _b) (Monge et al., (2025). What does IRT tell us about the evolutionary potential of heat tolerance in endotherms? <i>Evolution Letters</i>, 9(2),184-188). Here, we discuss the biological inferences that can be made from data on <i>T</i> _s and <i>T</i> _b, and whether <i>T</i> _s needs to be correlated with <i>T</i> _b to be informative in studies of thermoregulation in free-living organisms. We also present a framework illustrating biological insights that can be gained by integrating IRT with data on different phenotypic traits, fitness metrics, pedigree information and other physiological traits, including <i>T</i> _b. We illustrate the utility of this new framework by demonstrating how it has increased our understanding of the evolution of thermal tolerance in a large animal where <i>T</i> _b is not easily measured, the ostrich (<i>Struthio camelus</i>) (Svensson et al., (2024). Heritable variation in thermal profiles is associated with reproductive success in the world's largest bird. <i>Evolution Letters</i>, 8(2), 200-211). Integrating IRT with individual fitness data and pedigree information in field studies can aid our biological interpretation of <i>T</i> _s in future research on the ecology and evolution of thermal tolerance in both endotherms and ectotherms.