Exhaled air temperature and water conservation in lizards

Studies of the desert iguana ( Dipsosaurus dorsalis) show that a significant amount of water can be saved by exhaling air at temperatures below body temperature. When body temperature is near-equal to ambient air temperature the exhaled air is about 0.5 °C below body temperature, but when body temperature is higher than ambient air temperature (as in nature when the lizards bask in the sun) the exhaled air is cooled by several degrees. For example, a lizard with its body temperature maintained at 42 °C in air at 30 °C (r.h., 25 %) exhales air at 35 °C and recovers 31 % of the water that would have been lost if air were exhaled saturated at body temperature. The mean body temperature of active lizards in the field has been found to be about 42 °C (even when the air is much cooler), and the ability to exhale air at a lower temperature is therefore of great importance in their water balance.