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°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°to 45°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°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°C and was 43°C at T(a) of 45°C. At T(a) of 40°C bats increased dry thermal conductance and evaporative heat loss compared to lower T(a). At 45°C dry thermal conductance was lower than at 40°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(b). 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.