Metabolism and thermoregulation of individual and clustered long-fingered bats, Miniopterus schreibersii, and the implications for roosting

Oxygen consumption of individual long-fingered bats, Miniopterus schreibers ii, was measured at air temperatures (T-a) between 2 and 42 degrees C and t hat of clusters of four and six bats between 5 and 30 degrees C. BMR of ind ividuals was estimated to be 2.29 mi O-2 g(-1) h(-1) between 34 and about 3 8 degrees C. M. schreibersii showed two different responses to T-a, either maintaining body temperature (T-b) by increasing metabolic rate, or allowin g T-b to fall close to ambient temperature and conserving energy (torpor). Euthermic dusters of four and six bats had lower rates of mass-specific oxy gen consumption and lower thermal conductances than individuals at equivale nt temperatures and torpid clusters maintained a greater temperature differ ential between T-b and T-a. Lowest rates of metabolism were measured for eu thermic bats at air temperatures higher than those available to them in the ir natural roost in summer, so typical roost temperatures result in metabol ic rates that are about 2.4-3.1 times estimated BMR. Roost temperatures of M, schreibersii in South Africa are substantially higher in winter than are generally accepted as being suitable for hibernation but these do not subs tantially affect torpid metabolic rates. which are low and independent of a mbient temperature below 22 degrees C. Clearly at least some species of ins ectivorous bats are capable of hibernating at temperatures generally consid ered to be too warm for this activity.