Temperature and Humidity of Expired Air: Interspecific Comparisons and Significance for Loss of Respiratory Heat and Water from Endotherms

Abstract

The temperature of expired air at the external nares of black-tailed prairie dogs (Cynomys ludovicianus) was measured at inspired (ambient) air temperatures of 25, 30, 35, and 40 C, and over a broad range of humidities at each temperature. Expired air temperature was positively related to inspired air temperature and humidity; comparisons with published data for banner-tail kangaroo rats (Dipodomys spectabilis), deer mice (Peromyscus maniculatus), house mice (Mus musculus), and Australian hopping mice (Notomys alexis) showed similarities and differences among coefficients of multiple linear regressions describing analogous relationships. Simulations for a hypothetical mammal suggested how differences in the recovery of respiratory heat and water in nasal passages, and the loss of respiratory heat and water from the nose, should be affected by different relationships between the temperature of expired air and the temperature and humidity of inspired air.