Thermoregulatory behaviour of tree-roosting chocolate wattled bats ('Chalinolobus morio') during summer and winter

Abstract

The thermal physiology of tree-roosting bats has been rarely studied in the wild. I used temperature telemetry to locate and record the skin temperature (Tskin) of chocolate wattled bats ('Chalinolobus morio', Vespertilionidae) roosting in tree cavities. In summer, male 'C. morio' (n = 4) used torpor on 88% (15 of 17) of days. Bats entered torpor before or near sunrise, remained torpid for 7.3 h ± 3.8 SD (range: 0.8–13.2 h), and aroused midmorning. Torpor bout duration was negatively related to minimum torpid Tskin (R² = 0.94, P < 0.001). In winter, a female bat employed prolonged torpor lasting 13.5 and 15 days, during which Tskin fluctuated passively by 5.7°C ± 2.5°C, following the daily temperature cycle. At the same time of year, a male bat used torpor repeatedly but aroused on most evenings, possibly to find and copulate with females and also forage on warmer nights. These data shows that male 'C. morio' frequently enter torpor in summer and provides the 1st direct evidence of winter hibernation by tree-roosting bats.