Evaporative cooling via panting and its metabolic and water balance costs for lizards in the American Southwest.

In lizards there is considerable variation in the ability to dissipate environmental/endogenous heat loads through evaporative cooling via panting, which effects how long lizards can spend exposed to high solar heat loads. We recently described the differing capacities of lizards to depress body temperature (Tb) through evaporative cooling via panting. Here, we link panting and Tb depression with rates of evaporative water loss and its metabolic costs under high heat loads.

The functional significance of panting as a mechanism of thermoregulation and its relationship to the critical thermal maxima in lizards.

Because most desert-dwelling lizards rely primarily on behavioral thermoregulation for the maintenance of active body temperature, the effectiveness of panting as a thermoregulatory mechanism for evaporative cooling has not been widely explored. We measured changes in body temperature () with increasing air temperature () for 17 species of lizards that range across New Mexico and Arizona and quantified the temperatures associated with the onset of panting, and the capacity of individuals to depress below while panting, and estimated the critical thermal maxima (CT) for each individual. We examined these variables as a function of phylogeny, body mass and local acclimatization temperature.