(Rodentia: Bathyergidae)

Small rodents with a large surface-area-to-volume ratio and a high thermal conductance are likely to experience conditions where they have to expend large amounts of energy in order to maintain a constant body temperature at low ambient temperatures. The survival of small rodents is thus dependent on their ability to reduce heat loss and increase heat production at low ambient temperatures. Two such animals are the social subterranean rodents Cryptomys damarensis (the Damaraland mole-rat) and Cryptomys hottentotus natalensis (the Natal mole-rat). This study examined the energy savings associated with huddling as a behavioural thermoregulatory mechanism to conserve energy in both these species. Individual oxygen consumption (VO2) was measured in groups ranging in size from one to 15 huddling animals for both species at ambient temperatures of 14, 18, 22, 26 and 30 °C. Savings in energy (VO2) were then compared between the two species. Significant differences in VO2 (p < 0.05) were found within each species, indicating that both Damaraland mole-rats and Natal mole-rats saved more energy in larger as opposed to smaller groups. VO2 was also different between the two species, with Damaralan