INFLUENCE OF TORPOR ON DAILY ENERGY-EXPENDITURE OF THE DASYURID MARSUPIAL SMINTHOPSIS-CRASSICAUDATA

Daily torpor is an energy-conserving mechanism, used by many small mar supials to reduce energy expenditure during adverse environmental cond itions, Since little is known about how much energy is actually saved by torpor in marsupials anti how this is related to the duration of to rpor bouts, we investigated the effect of ambient temperature (T-a) on different metabolic states and the effect of torpor bout duration in Sminthopsis crassicaudata (16 g) on average daily metabolic rate (ADMR ), T-a had a significant effect on the active and resting metabolic ra tes (MR), both being higher at T-a 12 degrees C than T-a 18 degrees C (P < 0.001, t-test), In contrast, the ADMR at T-a, 12 degrees C and T- a 18 degrees C did not differ significantly, and it appears that the i ncreased cost for thermoregulation in normothermic active and resting animals at T-a 12 degrees C was compensated by a decrease in MR during torpor. Torpor bout duration was negatively correlated with ADMR, Tor por bouts of 5 hr reduced ADMR by 12-16%, Torpor bouts of more than 10 hr reduced ADMRs by 30-50%, Our study shows that torpor can significa ntly reduce daily energy expenditure in S. crassicaudata, and this may be important for the survival of this species in the wild.