Thermoregulation, energy metabolism, and torpor in blossom-bats, Syconycteris australis (Megachiroptera)

Since little information is available on torpor in bats of the suborder Megachiroptera, we investigated whether the small(18 g) blossom-bat Syconycteris australis displays torpor in the laboratory. Bats entered daily torpor when food and water were withheld for one night and the air temperature (T-a) was below about 26 degrees C. Torpor began shortly after lights went on in the morning and lasted for a maximum of 12 hours. During torpor at T-a 18 degrees C, metabolic rates fell to a minimum of about 15% of that in resting individuals at the same T-a, and to about 40% of the basal metabolic rate. The body temperature (T-b) during torpor was metabolically defended at or above about T-b 18 degrees C. Individuals that did not enter torpor in the morning reduced their T-b from about 34.5 degrees C, observed in resting individuals that had been fed during the previous night, to values between 30.2 and 32.8 degrees C, and the resting metabolic rate fell by about 25%. The ability to undergo short periods of torpor may explain why the distribution range of S. australis extends much further south than that of other small Australian megachiropteran bats.