Nasal heat exchange in the giraffe and other large mammals

Abstract

The respiratory air of the giraffe is exhaled at temperatures substantially below body core temperature. As a consequence, the water content of the exhaled air is reduced to levels below that in pulmonary air, resulting in substantial reductions in respiratory water loss. Measurements under outdoor conditions showed that at an ambient air temperature of 24 degrees C, the exhaled air was 7 degrees C below body core temperature, and at ambient air temperature of 17 degrees C, the exhaled air was 13 degrees C below core temperature. The observations were extended to two additional species of wild and four species of domestic ungulates. All these animals exhaled air at temperatures below body core temperature. The average amount of water recovered due to cooling of the air during exhalation, calculated as per cent of the water loss that would occur if air were exhaled at body core temperature, amounted to between 24 and 58%, the average value for the giraffe being 56%.