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Data and code from: Dialect formation in ghost bats: Genetic, geographic, and morphological drivers of social and echolocation call divergence

Hanrahan, Nicola12; Armstrong, Kyle34; Turbill, Christopher1; Dalziell, Anastasia1; Welbergen, Justin1

Published Apr 22, 2026 on Dryad. https://doi.org/10.5061/dryad.kprr4xhjf

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Apr 22, 2026 version files 15.68 MB

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Abstract

Geographical patterns of vocal dialects are poorly understood in bats, despite growing evidence that they possess complex vocal communication systems.

We investigated patterns and drivers of variation in vocalisations recorded at five ghost bat colonies in the Northern Territory, Australia. We calculated the genetic and morphological distances among individuals and investigated correlations with geographic distance. We then determined variation within three ghost bat social vocalisations (“Chirp-trill”, “Squabble”, “Ultrasonic Social”) and their “Echolocation” call using seven spectrographic measurements. Finally, we tested whether acoustic distance could be explained by genetic, geographic, or morphological distance.

Geographic and genetic distance were highly correlated, suggesting the occurrence of isolation by distance. All measures of morphological distance were consistent with Bergmann’s Rule, except noseleaf shape, which is likely constrained by its role in echolocation. Geographic variation was evident within each of the three social vocalisations and the echolocation call, with the patterns of geographic variation differing among the four vocalisation types. The degree of difference was surprising, given the ghost bat’s long-range seasonal dispersal. Acoustic distance in Chirp-trill and Squabble calls was marginally significantly correlated with genetic (and geographic) distance. In contrast, Ultrasonic Social and Echolocation calls varied among colonies but showed no significant associations with other metrics, apart from a weak correlation between Ultrasonic Social distance and forearm length. This supports the view that these ultrasonic calls are under stabilising selection due to their role in foraging and orientation.

This study provides the first evidence of dialect formation in megadermatid bats. It highlights the importance of considering multiple vocalisation types and investigating multiple processes in signal evolution. Overall, we found genetic, geographic, and morphological distances accounted for some of the variation in acoustic differences among colonies, but further work is needed to investigate other processes that may also contribute to dialect formation in ghost bats.