Natural History Miscellany Lizard Thermal Biology: Do Genders Differ?

For more than six decades, physiological ecologists have intensively studied diverse aspects of lizard thermal biology. Nevertheless, a recent review notes that prior studies have generally ignored gender differences in body temperatures, thermal sensitivity, or other aspects of thermal biology. We concur that gender differences have been ignored and should be examined: if gender differences prove common, standard protocols for studying lizard natural history, thermal physiology, and ecology will require significant modification. To help resolve this issue, we conducted a retrospective analysis of our huge data set on the thermal biology of many desert lizards (more than 11,000 individuals from 56 species in seven major clades) from Africa, Australia, and North America. Results are unambiguous: gender differences in body temperature, air temperature, and time of activity—and thus in field thermal biology—are almost always minor. In fact, mean body temperatures of males and females differ by less than 1 C in 80.4% of species. For desert lizards, gender differences in thermal biology are the exception, not the rule. Nevertheless, gender differences should be examined when feasible because exceptions—though likely rare—could be biologically interesting.