The effect of cave microclimate on winter roosting behaviour in the bat, Miniopterus schreibersii blepotis

The microclimate at Thermocline Cave (lat, 30° 45′S, long, 149° 43′E) was investigated by measuring air temperature and relative humidity at five stations on 18 occasions from September 1971 to December, 1973. The activity, body weight and roosting sites of the bat Miniopterus schreibersii blepotis in the cave were recorded on each visit. Relative humidity in the cave was generally high and paralleled temperature. The cave exhibited a range of temperatures from 9 to 19.5°C but bats selected roosting sites only in a part of this range. During the autumn when the bats arrived and were feeding, their body weights were low, and they roosted in a domed area at the rear of the cave with a temperature of 19.5°C. As they became less active and body weight increased they moved to cooler parts (9.5‐11°C) towards the front of the cave and underwent periods of torpor, in one case lasting for at least 12 days. From July to September body weight decreased. The bats became more active in September and most had left the cave by October. It appears that M.s. blepotis can detect temperature differences of 1°C. They used this ability to select cold areas with stable high humidity in Thermocline Cave to under go periods of winter torpor. Copyrigh