Listening to the bats of Caraj&aacutes: Applied bioacoustics for species inventory and environment use in a mosaic of forests, savannas, and industrial mining in the Brazilian Amazonia

Bats emit echolocation calls for orientation, foraging, and social interactions. These calls are mostly species-specific, reliable for inventories and to assess habitat use, characteristics useful for large, species-rich but poorly sampled areas. This is the case of Carajas, in Brazilian Amazonia, a mosaic of cave-rich dense forests and unique metalophilous savannas (known as canga), harboring a rich bat fauna but also industrial iron ore mining, stressing the need to preserve biodiversity. We used bioacoustics (142,000 minutes of recording) to inventory bats at 61 points in Carajas and identified 43 sonotypes of seven bat families, including species rarely recorded with capture nets. Eleven species were recorded for the first time in Carajas. Species richness varied among environments - forests being the richest - but cangas had greater richness stability and a more distinct species composition. All areas with imminent mining had high bat richness. Richness in a post-mined area increased, possibly indicating resilience of some species. By providing a reference sound library for bats in Carajas, we proved the usefulness of biacoustics to improve the environmental licensing processes involving mining in biodiversity-rich areas, useful not only for Amazonia but also for other tropical environments with high bat species richness.