THERMAL BIOLOGY AND METABOLISM OF THE GREATER LONG-EARED BAT, NYCTOPHILUS MAJOR (CHIROPTERA, VESPERTILIONIDAE)

Nyctophilus major is the largest member of its Australian-centred genu s. Plow-through respirometry was used to investigate the thermal and m etabolic physiology of adult N. major from south-western Australia. Ox ygen consumption, carbon dioxide production, respiratory quotient, eva porative water loss and thermal conductance were measured at ambient t emperatures of 5-40 degrees C. N. major was thermally labile and could be euthermic or torpid at low T-a. N. major entered into and spontane ously aroused from torpor at T(a)s as low as 5 degrees C, and became t orpid at T(a)s as high as 23 degrees C. Like other temperate-zone Aust ralian vespertilionid bats, some torpid N. major maintained a relative ly high T-b at low T-a. Body mass and the duration of captivity had no detectable effect on the thermal responses of bats. The basal metabol ic rate (BMR) of N. major was 85% of predicted, and falls within the t he range of mass-specific BMRs reported for vespertilionid bats. While mean torpid (V) over dot O-2 was reasonably high, torpor still facili tates substantial metabolic savings. However, because of the high (V) over dot O-2, N. major may not be able to remain torpid for more than about 60 days, relying solely on fat reserves. The evaporative water l oss (EWL) of euthermic and torpid N. major was also high, although EWL during torpor was reduced compared with euthermy. Wet conductance was lower than predicted and probably relates to the solitary, tree-roost ing habits of N. major. As has been reported for other bats, conductan ce values during torpor were lower than those during euthermy, but whe n torpid bats maintained a large (T-b - T-a) differential at low T-a o r became torpid at relatively high T-a, conductance values approached euthermic levels.