Species richness, occurrence and rarity of bats in Brazilian caves

Abstract

Caves are among the most important roosts of hundreds of bat species worldwide. However, caves can be formed in different lithologies. Cave structure and characteristics, which are shaped by lithology, can, in turn, influence roost preferences for different bat species. Therefore, cave lithology and characteristics can help us to better understand why some bat species may be rare in some caves and common in others. Brazil is a continental country, rich in bat species (181 spp.), lithologies and caves (>23 000). However, only a small fraction of the known caves has been sampled for bats so far, with no emphasis on the role lithology may have. Based on a literature review and using data on bat occurrence, in this study, we investigated the influence of lithology on bat species richness and rarity in Brazilian caves. We evaluated 117 studies, including data from 552 caves, and updated the number of bat species occurring in Brazilian caves to 81. Species richness differed between lithologies: carbonate caves had higher species richness, whereas iron caves had lower species richness. Richness was positively related to carbonate caves and with cave size: the bigger the cave, the more species-rich it tends to be. Overall, caves in the Cerrado had the highest species richness, followed by Atlantic Forest, Caatinga caves and Amazonian caves. Thirteen species can be considered as primarily cave-dwelling species, recorded in 10%–20% of the caves. Rarity was common among primarily cave-dwelling species. Nearly 22% of the sampled caves harboured endangered species, reaching 53% of the species-richest caves. Our analysis provides a comprehensive baseline for bat fauna in different types of caves in Brazil. Even so, we strongly recommend the establishment of long-term monitoring of population trends for bats in Brazilian caves, which is necessary information but almost non-existing for the country.