DISTRIBUTION, ABUNDANCE AND ROOST SELECTION OF THE ORANGE HORSESHOE-BAT, RHINONYCTERIS-AURANTIUS, A TROPICAL CAVE-DWELLER

Temperature and humidity were recorded from roost sites used by nine species of cave bats in northern Australia. The 10 sites containing R. aurantius exhibited the narrowest range of roost conditions of any species, this species having a strong preference for hot and humid roosts (28-32-degrees-C and 85-100% RH). R. aurantius colony sizes ranged from 20 to 25 000, and varied seasonally, almost all colonies abandoning their cave roosts during the wet season. Colony size was strongly related to mean minimum monthly temperature and rainfall, populations being greatest during the coolest and driest period of the year. Other sympatric species also exhibited preferences for specific roost conditions, indicating interspecific partitioning of roost resources. Species that utilised a broad range of roost humidity occupied a larger geographic range than those with more specific requirements.