Thermal energetic profiles as a function of the maximum range of ambient air temperatures (Ta) over which normothermia could be maintained, were measured in an arboreal rodent, Thallomys paedulcus, and a burrow-dwelling rodent, Aethomys namaquensis, during the rest- and activity-times, and in summer- (LD 16:8, 30°C) and winter-acclimated (LD 8:16, 20°C) animals. Both species had minimal wet thermal conductances (Cmin) ca 42% of expected values, and thermoneutral resting metabolic rates (TRMR) 54–64% of expected values. It is proposed that the low Cmins are required to maintain thermal balance at the lowest daily Tas, whereas the low TRMRs are required to avoid hyperthermia induced by high daily Tas and the low Cmin values. Burrowing behaviour did not seem to influence the selection of these low parameters per se, but did require large seasonal fluctuations in the endothermic temperature range - the maximum range of Ta over which the animal maintained normothermia below thermoneutrality. It is suggested that a continuum may exist between the water-economy hypotheses and our endothermic temperature range hypothesis, dependent upon the refugia used, diet, water availability, and heat tolerance.