The roosting site of the frugivorous bat, Rousettus leschenaulti of the Ṭawi Wildlife Sanctuary was surveyed and the population was determined. The abiotic parameters such as temperature, relative humidity, light intensity, roosting area, the structural details of roosting site, etc. as well as the biotic parameters such as the composition of age and sex, roosting pattern, seasonal variation in the roosting behaviour, etc. were determined. The roosting site, RS was occupied by a colony of over 1215 individuals. The variation in light intensity (0.2–0.8 lux), temperature (28 ± 0.2oC) and relative humidity (94 ± 1%) was least in this roosting site because of the closed and insulated nature of the roost. This is a specious and dark roosting site. These bats roosted in four types of clusters namely mixed-sex adults, mixed-sex sub-adults, pregnant females with lactating mothers, and the mixed-sex old individuals. The formation of clusters was based on the sex, age and reproductive status of individuals. The sex-bias favoured females.