Roost microclimates of the bat Rhinonicteris aurantius in a limestone cave in Geike Gorge, Western Australia

Abstract

THE orange leaf-nosed bat, Rhinonicteris aurantius, has been poorly studied in the Kimberley region of Western Australia. The range of R. aurantius is continuous across the tropical north of Australia, extending throughout the Kimberley region and the Top End of the Northern Territory. Within this distribution, the species is reported to be rare and restricted to a few sites (Churchill 1991a). This pattern of distribution is due to a reliance on caves with warm, humid roost microclimates. Jolly (1988) and Churchill et al. (1988) recorded a narrow range of preferred roost temperature and relative humidity (RH) in the Northern Territory of between 28-32ºC and 90-96% respectively, although Churchill (1991a) recorded RH in roosts of R. aurantius of between 85- 100% (30.43 ± 2.18 g m^-3 vapour density). The species also tends to roost as far from the entrance as possible, which is often correlated with such extreme microclimate variables (Jolly 1988; Churchill 1991). The roost microclimate of R. aurantius in July 1987 in a medium-sized limestone cave near Geike Gorge (18º 06’S 125º 42’E) was recorded as 29.5ºC and 28.44 g m^-3 (Churchill 1991b), within the preferred range of R. aurantius.