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1. Oxygen consumption (V(O2)), thermal conductance (C(d) and C(min)), body temperature (T(b)) and evaporative water loss (EWL) of the Cape gerbil Tatera afra were measured at ambient temperatures (T(a)) between 5 and 35-degrees-C.

2. T. afra is not well adapted to high T(a). Above 30-degrees-C, hyperthermia occurs, despite elevated C(d), C(min). and EWL. Peripheral vasodilation, salivation and urination are short term responses that contribute to delaying the onset of hyperthermia.

3. The water turnover rate (WTR) is higher (48%) in the field than in the laboratory owing to activity associated with foraging behaviour, predator avoidance and socialization. The relatively mild and mesic environment permits a higher WTR than in arid zone gerbils.

4. Basal metabolic rate (BMR) is higher (49%) than the average value for other cricetid rodents. It is hypothesized that this is associated with herbivory and a relatively low T(a).