Population size and emergence order of R. aegyptiacus were studied in the Abas cave. Haifa, Israel. Throughout the reproductive period adult females populated the cave and the adult population consisted mainly of adult females except during winter when higher numbers of adult males were recorded. The proportion of juveniles increased consistently from spring to winter. Thus, it is suggested that the Abas cave serves as a maternity roost. Adult females in the reproductive state emerged from the cave earlier that juveniles and adult males. Social factors and differences in nutritional demands which may correspond to this different emergence order are discussed.