Sex ratio, population structure and roost fidelity in a free-ranging colony of Indian false vampire bat, Megaderma lyra

We studied sex ratio, population structure and roost fidelity in Indian false vampire bat, Megaderma lyra for four years using mark-recapture method, in a free-ranging colony at Pannian cave, Madurai, South India. Jolly-Seber analysis of mark-recapture data showed variable fluctuation in population size of both sexes. The population size from 2001 to 2004 varied from 138 to 37 for males and 213 to 61 for females. In all the years, females outnumbered males and sex ratio ranged between 0.2 and 0.3. Compared to males, females exhibited low roost fidelity, and also showed high percentage of emigration across four years. However, there is no significant difference in percentage of immigration between the sexes. We predict that bats exhibit sexually dimorphic dispersal behaviour that depends on time and space, similar to other mammals and we hypothesize a few reasons for this dispersal, including population density, habitat destruction and inbreeding avoidance.