This week several bat experts from BUNDIS (German Friends of the Earth) visited the forest discussed and shared information on bat behaviour and their population pressures in the shrinking forest. The group that has evicted tha bats and mice by blocking their habitats has refused to engage us in this discussion reregardless of many requests and calls to discuss and explain their animal evictions in front of the harvesters by setting up a bogus claim that now there is no endangered bats in the forest about to be cut. This group is not only sponsored and paid by RWE but it was also discovered during this visit that their claims that they are affiliated and aproved by BUND were misrepresentation and were untrue.
The walk with infra-red camera looked at and for evidence of plastic covered holes being reopened by animals, fluid and smell comig from the opening indicating that animals were closed in inside. As a result of all the above evidence being found across the forest as many closed openings as possible were re-opened.
As far as I know a good way to monitor bats is to use bat detectors which convert the ultrasound emitted by the bats into human hearable frequencies. I think you walk around with such a detector and see where bats are to find. You can even distinguish different bat species by using this method.
Of course, this has to be done at night when the bats are active.
I also know that in some forests there are nesting boxes for bats (very similar to bird nesting boxes) e. g. placed on trees.
Of course, this would only make much sense if the forest is safe from cutting.