Geographic variation of sexual selected male traits is common in animals. Female choice also varies geographically and several studies found female preference for local males, which is assumed to lead to local adaptation and therefore increases fitness. As females are the non-dispersing sex in most mammalian taxa, this preference for local males might be explained by learning of male characteristics. Studies on preference of females in female-dispersing species are lacking so far. To find out whether such females would also show preferences for local males, we conducted a study on greater sac-winged bats (Saccopteryx bilineata), a species where females disperse and males stay in their natal colony. Male greater sac-winged bats possess a wing pouch that is filled with odoriferous secretion and fanned towards females during courtship display. In a combination of chemical analysis and behavioural preference tests, we analysed whether the composition of wing sac secretion varies between two geographically distinct populations (300 km), and whether females show a preference for local or distant male scent. Using gas-chromatography, we found significant differences in the composition of the wing-sac odours between the two geographic distinct populations. In addition, the behavioural preference experiments revealed that females of both populations preferred scent of geographically distant males over local males. The wing-sac odour might thus be used to guarantee optimal outbreeding when dispersing to a new colony. This is – to our knowledge – the first study on odour preference of females of a species with female-biased dispersal.

We collected odour samples from the males by wiping each of the two wing sacs with a piece of cotton of ∼5mg that had previously been washed with dichlormethane (DCM; 99.9%) to remove potential contaminating substances. We stored the samples individually in Teflon-capped glass vials (2 ml Rotilabo, Karlsruhe, Germany) at -20°C until further use.

Samples were stored at -20°C prior analysis. All samples were prepared for analysis and analysed at Bielefeld University, Department of Behavioural Ecology. Prior to chemical extraction, we first defrosted the samples for a minimum of 60 min under laboratory temperature (22 °C). After the samples had ambient temperature we added 100µl of DCM. Samples were then extracted by squeezing out the cotton dapper using a blunt point syringe (100 µl, ILS, Stützerbach, Germany). We transferred each extract into a glass vial (2 ml, Rotilabo®, Karlsruhe, Germany) that was equipped with a 100 µl inlet (Rotilabo®, Karlsruhe, Germany). The extracts were concentrated by evaporation to approximately 5 µl before analysis.

These samples were analysed by gas chromatography (GC-FID, Shimadzu GC 2010) equipped with a VF-5ms capillary column (30 m x 0.25 mm ID, DF 0.25, 10 m guard column, Varian Inc., Lake Forest, California, USA). Therefore, one μl of each sample was injected into a deactivated glasswool-packed liner at an inlet temperature of 220 °C and processed in a split 10 mode with 20 ml/min split flow. Hydrogen was used as carrier gas and its flow rate was held at 1 ml/min. The GC temperature started at 60 °C initial time of 3 min, followed by a 10°C/min rate to a final temperature of 280 °C, which was kept for 20 min. To compare the composition of wing sac chemical fingerprints, we used all substances that were absent in the cotton blank samples and present in at least in two greater sac-winged bat samples, i.e. we removed those substances that were found in one sample, only.  In total, we identified 282 different putative substances, which were found at least in two samples. Substances were aligned based on retention time using the R-Skript GCAlignR (Ottensmann et al. 2018).