Responses of Xeric-Adapted Rodents to Waterloading. ∗

Summary

Dipodomys merriami, D. agilis and Meriones unguiculatus excreted orally administered water loads at rates slower than those reported for white rats. Dehydrated animals retained all, or almost all, of an initial load of 5 ml/100 g for at least 6 hours. Animals fed lettuce before loading excreted 40% of the load in 123 to 504 minutes; rate of excretion was inverse to the aridity of the species' habitats. The rate of diuresis doubled or tripled after a second or third loading, but a residue of conservation remained. None of the species showed “difficulty in excretion” after being conditioned by the first loading.