Thermoregulation in the Angolan free-tailed bat Mops condylurus:: A small mammal that uses hot roosts

The Angolan free-tailed bat (Mops condylurus) uses roosts that often exceed 40 degrees C, an ambient temperature (T-a) that is lethal to many microchiropterans. We measured the physiological responses of this species at T-a's from 15 degrees to 45 degrees C. Torpor was commonly employed during the day at the lower T-a, but the bats generally remained euthermic at night, with a mean body temperature (T-b) of 35.2 degrees C. Metabolic rate reflected the pattern of T-b, increasing with falling T-a at night but decreasing during the day. Metabolic rate and evaporative losses were lower in torpid than in euthermic bats. Body temperature increased at each T-a >35 degrees C and was 43 degrees C at T-a of 45 degrees C. At T-a of 40 degrees C bats increased dry thermal conductance and evaporative heat loss compared to lower T-a. At 45 degrees C dry thermal conductance was lower than at 40 degrees C and evaporative heat loss was 132% of metabolic heat production. At high T-a there was only a slight increase in metabolic rate despite the employment of evaporative cooling mechanisms and an increase in T-a. Collectively our results suggest that M. condylurus is well suited to tolerate high T-a, and this may enable it to exploit thermally challenging roost sites and to colonise habitats and exploit food sources where less stressful roosts are limiting.