Echolocation is used for navigation and foraging by more than 87% of bat species. Echolocation call analysis helps to identify bat species and provides insights into their ecology. Identifying species from echolocation calls is challenging because their call structure is influenced by their environment as well as by their phylogeny.

Habitat features influence bat echolocation, with calls adapting to different environments. When flying in cluttered environments, such as forests, bats typically use short duration and broad bandwidth calls. These frequency-modulated (FM) calls enhance navigation through clutter by providing high resolution of detail. In contrast, in open spaces bats use longer duration and narrow bandwidth calls, which provide more information about distant objects. In forest edge environments, where bats require both resolution and detection distance, they use calls where an FM sweep turns into a quasi-constant frequency component (FM-QCF calls). Additionally, diet and foraging strategy further shape call structure, with differences between aerial hawkers, which chase prey in flight, and gleaners, which capture prey from surfaces such as leaves.

In the process of building a reference library to aid species identification in acoustic surveys, inspection of spectrograms revealed that Myotis pruinosus and Pipistrellus endoi emit very similar FM/QCF call shapes. This is very unusual for a Myotis species as the vast majority emit FM calls. Based on this observation, we sought to statistically test for similarities. This study aimed to demonstrate the similarities between two species of differing genera, M. pruinosus and P. endoi. Previous recordings of Myotis and Pipistrellus species were available from hand-released and free-flying bats from various locations in Japan. These included Aridagawa, Wakayama; Ashiu Forest, Kyoto; Nakagawa, Hokkaido; Nijo Castle, Kyoto, and Yakushima, Kagoshima. A Canonical Discriminant Analysis (CDA) was carried out to test for differences in acoustic parameters (Fmin, Fmax, Fmean) of the echolocation calls. The CDA and subsequent confusion matrix revealed an overlap between M. pruinosus and Pipistrellus species, particularly P. endoi which reinforces observations from spectrograms. This highlights acoustic convergence between these two species, which potentially provides evidence for convergent evolution. Further ecological studies into M. pruinosus may reveal why it has this call type and open avenues for developing acoustic methods for monitoring this Endangered species.