Here’s a cool new environmental DNA (eDNA) paper where the researchers (Garrett et al. 2023) used airborne DNA to detect bats in their roosts.
Title: Out of thin air: surveying tropical bat roosts through air sampling of eDNA
All of the detected bats (some rather rare) are known from previous work in the area. The authors also note non-target eDNA that likely drifted into some roosts (e.g. cow eDNA). However in some cases the non-target eDNA detections likely were from species actually associating with bats.
eDNA is a great method for detecting hard-to-access species, and this is a good demonstration of its utility.