WOODLEY , R.; BUFFENSTEIN, R.*: Reproductive function of naked mole-rats is extremely sensitive to ambient temperature.

Naked mole-rats (Heterocephalus glaber), are thermoconforming mammals. Effects of a 5°C decline in ambient temperature (Ta) on gestation, fecundity and maternal body composition and temperature (Tb) were assessed by comparing animals housed at 25°C (CA) and simulated burrow conditions (SBT; 30°C). Pregnant females at SBT were also subjected to acute 5-day cold bouts during early (EP), mid (MP) or late (LP) pregnancy, to determine at which stage they are most sensitive. Predictably, Tb of CA animals was lower than that of females at SBT, although the pregnant temperature differential (Tb-Ta) was greater (CA,7°C; SBT,4°C). Reproductive success of CA females declined more than 4-fold (P<0.001). The interbirth interval was prolonged (CA, 152±77days; SBT, 77±2days; P<0.001), with evidence that gestation length was also extended (CA, 76± 5days; SBT, 68±2days; P<0.001). Although litter size was unchanged with CA, pup mass (1.70±0.3g) in the cold was greater (P<0.05) than at SBT (1.49±0.27g). CA pup growth rate post-weaning was 38% lower, but no difference in pup mortality was noted. At all stages of pregnancy, females lost mass during acute cold bouts. 94% of this was due to fat loss, with lean mass only drawn upon during early pregnancy. The interbirth interval with acute cold bouts was highly variable, particularly when cold bouts occurred during EP and MP. Clearly, reproductive function in these thermoconforming mammals, like that of most poikilothermic vertebrates, is extremely sensitive to ambient conditions.