Metabolism and Thermoregulation in the Cape Porcupine,Hystrix africaeaustralis

Abstract

Oxygen consumption (V̇o2) and body temperature (Tb) were measured at various ambient temperatures (Ta) between 13° and 39° C in individuals of the Cape porcupine (Hystrix africaeaustralis), acclimated to Ta = 25° C at a controlled photoperiod of 12L:12D. V̇o2 of this species in the thermoneutral zone (Ta = 24°–27° C) is only 5796 of the V̇o2 of an 11.1 ± 0.7 kg mammal aspredicted by Kleiber. Tb was well regulated up to Ta = 30° C. Hyperthermia was observed at Ta above 30° C. Tb regulation was accompanied by an increase in overall thermal conductance and respiratory frequency rate. Overall minimal thermal conductance calculated at lower critical point Ta = 24° C is higher than predicted by Bradley and Deavers. Apparently digestible dry-matter intake and gross digestible energy intake are relatively low and correlate with the low V̇o2 values recordedfor this species. Water intake in this species is significantly lower than that of the crested porcupine (H. indica) under similar conditions. Low metabolic rates on the one hand and high overall thermal conductance on the other appear to be importantphysiological adaptations for this large, burrowing, nocturnal rodent, which has a wide ecological tolerance.