Complex reproductive and migratory patterns in the European free-tailed bat (<i>Tadarida teniotis</i>) (Molossidae)

Abstract Reproductive strategies vary widely among bats, even within the same species. The molossid Tadarida teniotis has an intermediate latitudinal distribution between tropical bats and those of temperate zones. There are still some uncertainties about its migratory behaviour and reproductive mode that are not yet fully understood. Some authors believe that this species breeds in spring and is sedentary, while others propose a bimodal breeding cycle with occasional or partial migration. In this paper, these contradictory approaches are exposed, providing more data to help solving this controversy. The results of the species monitoring for several years verified the existence of harems in spring and summer-autumn in at least one location of its range (Valladolid, central Spain). In both periods and during several months, males were observed performing patrols and displaying aggressive behaviour towards male intruders. This may have been facilitated by the peaks in migratory moth abundance. For the late parturitions occurring in autumn/winter and in case of absence of deferred reproduction mechanisms, a sex-biased migration is necessary for, at least, the females who got pregnant during the autumn mating. Thus, the species appears to show greater reproductive and migratory complexity than previously thought.