COMPARATIVE ASPECTS OF THE THERMAL BIOLOGY OF THE SHORT-TAILED GERBIL, DESMODILLUS-AURICULARIS, AND THE BUSHVELD GERBIL, TATERA-LEUCOGASTER

1. The response of oxygen consumption (VO2), thermal conductance (C-d and C-min), body temperature (T-b), and evaporative water loss (EWL) o f Tatera leucogaster and Desmodillus auricularis were measured over th e range of ambient temperatures (T-a) from 5-35 degrees C. 2. Basal me tabolic rate (BMR) of T. leucogaster was 0.841 +/- 0.049 ml O-2 g(-1) h(-1) and lower than predicted, while that of D. auricularis was simil ar to the expected value (1.220 +/- 0.058 ml O-2 g(-1) h(-1)). D. auri cularis had a high, narrow thermoneutral zone (TNZ) typical of nocturn al, xerophilic, burrowing rodents. 3. D. auricularis and T. leucogaste r regulated T-b over the range T-a = 5-35 degrees C and kept EWL and d ry thermal conductance at a minimum below the TNZ. However, the EWL of T. leucogaster increased rapidly above T-a = 30 degrees C.4. After co mparison with data from other species, it was concluded that there is an optimum size for xeric, nocturnal, burrowing rodents.