Abstract: Postnatal growth in H. ater was analysed based on the longitudinal sampling of individuals of known age. Periodic visits were made to the bat roosting sites and the bats were monitored. Young ones of H. ater were observed to have a body mass of 1.5 gm at their birth. Male and female young ones attain 72% (3.8 gm) and 76% (3.6 gm) of the adult body mass in an age of 46 days and 48 days, respectively. Behaviour pattern in parturient bats was observed and the period of labor in H. ater occurs for about 25-32 min.