Dispersion and site fidelity in a tent-roosting population of the short-nosed fruit bat (Cynopterus sphinx) in southern India

Patterns of dispersion and site fidelity were investigated in a tent-roosti ng population of the short-nosed fruit bat, Cynopterus sphinx (Megachiropte ra), in southern India. A local population of C. sphinx occupied diurnal ro osts in a variable subset of 45 stem tents constructed within the dense fol iage of mast trees (Polyalthia longifolia). Individually marked tent-roosti ng bats were visually censused over the course of a 38-d interval spanning the postpartum oestrus period. On any given day, 33.3-85.7% (mean = 60.8%, SD = 14.2) of adult males roosted singly, with the remainder holding harems of 1-10 breeding females (mean = 3.01, SD = 0.79). Average harem sex ratio was 2.8-fold higher than the adult sex ratio of the total tent-roosting po pulation within the study area, indicating the potential for a high varianc e in male mating success within a single breeding season. Bats of both sexe s typically occupied one primary tent, interspersed with shorter periods of residency in alternate tents. Males exhibited a significantly higher degre e of roost fidelity than females. Some females roosted sequentially with di fferent males and with different combinations of females, whereas others re mained continuously associated with a single male and/or particular female roostmates over the duration of the census period. There were no statistica lly significant relationships between physical, characteristics of rents an d rates of occupancy by males or females. Intermittent transfers by females between groups suggest that the defence of diurnal roosts by males represe nts a more profitable mating strategy than the direct defence of compositio nally labile female groups.