Sonotype-level responses of Afrotropical hipposiderid bats to local-scale effects of rainforest structure

Bats exhibit a variety of life-history traits that can serve as valuable surrogate metrics of terrestrial ecosystem health. Here, we investigate how sonotype activity of hipposiderid bats covaries with habitat structure at finer spatial scales. We recorded passive echolocation calls and measured key habitat attributes in six rainforests in the Lomami and Yangambi landscapes, Democratic Republic of the Congo. Using bat passes as a measure of sonotype activity, we clustered echolocation calls based on call structure similarity to control for within-sonotype variation in activity. Over 432 h of recording, we detected 370 passes matching a hipposiderid sonotype in three subgroups, recovering eight potential species. Open habitats negatively affected sonotype activity in the Hipposideros subgroup, which was associated with higher echolocation frequencies. Indeed, activity peaked in the early evening when mean post-sunset temperature was above the nocturnal average and declined until early morning when mean temperatures dropped below the nightly average. All habitat variables were marginally correlated with the activity of the Doryrhina subgroup, whereas Macronycteris was more active in open habitats. Our findings indicate a probable flexibility of habitat use in lower echolocating bats and point to three possible foraging guilds that modulate hipposiderid bat responses to habitat structure.