TEMPERATURE REGULATION AND METABOLISM OF AN AUSTRALIAN BAT, CHALINOLOBUS-GOULDII (CHIROPTERA, VESPERTILIONIDAE) WHEN EUTHERMIC AND TORPID

The thermal and metabolic physiology of Chalinolobus gouldii, an Austr alian vespertilionid bat, was studied in the laboratory using flow-thr ough respirometry. Chalinolobus gouldii exhibits a clear pattern of eu thermic thermoregulation, typical of endotherms with respect to body t emperature and rate of oxygen consumption. The basal metabolic rate of euthermic Chalinolobus gouldii is approximately 86% of that predicted for a 17.5-g mammal and falls into the range of mass-specific basal m etabolic rates ascribed to vespertilionid bats. However, like most ves pertilionid bats, Chalinolobus gouldii displays extreme thermolability . It is able to enter into torpor and spontaneously Introduction arous e at ambient temperatures as low as 5 degrees C. Torpid bats thermocon form at moderate ambient temperature, with body temperature approximat e to ambient temperature, and have a low rate of oxygen consumption de termined primarily by Q(10) effects. At low ambient temperature (< 10 degrees C), torpid C. gouldii begin to regulate their body temperature by increased metabolic heat production; they tend to maintain a highe r body temperature at low ambient temperature than do many northern he misphere hibernating bats. Use of torpor leads to significant energy s avings. The evaporative water loss of euthermic bats is relatively hig h, which seems unusual for a bat whose range includes extremely arid a reas of Australia, and is reduced during torpor. The thermal conductan ce of euthermic C. gouldii is less than that predicted for a mammal of its size. The thermal conductance is considerably lower for torpid ba ts at intermediate body temperature and ambient temperature, but incre ases to euthermic values for torpid bats when thermoregulating at low ambient temperature.