Reproductive seasonality of the Egyptian fruit bat (<i>Rousettus aegyptiacus</i>) at the northern limits of its distribution

Abstract We collected and analyzed data on the annual course of reproduction of the Egyptian fruit bat (Rousettus aegyptiacus) in 2 climatically distinct areas, the Mediterranean and the Egyptian desert, located at the northern limits of the species' distribution. In both regions, reproductive seasonality was characterized by distinct bimodality in birth timing regardless of climatic differences. A low incidence of simultaneous pregnancy and lactation indicated that both seasonal bimodal polyestry with and without postpartum estrus may occur in both regions, with a possibly lower incidence of postpartum estrus in females from the Mediterranean population. Observed shifts in birth timing between the Mediterranean and the desert study area corresponded to regional differences in fruiting phenology of major dietary plants. The male reproductive cycle was synchronized with that of females. The period of testicular recrudescence occurred during the peak pregnancy period. Because testis size was related to body mass irrespective of body size, we hypothesize that food abundance is an important trigger of male sexual activity. R. aegyptiacus is the sole species with seasonal bimodal polyestry among Palearctic bats.