So its not a great place for a human to be. What is it, then, about caves and other underground places that entice bats there in the first place?
There are two main reasons: stable climate and reliable shelter.
Bats large wings feature a lot of exposed surface area, making them prone to dehydration. Going underground allows them to move into areas with cooler temperatures and higher relative humidity. The underground is so climatically stable that some bats, like the Peruvian long-snouted bat (Platalina genovensium) can even live in the intensely dry Atacama Desert.
Caves and other underground structures are also persistent features on the landscape. Compare that with a tree snag or human construction, spots which might last a few years to several decades at best. A cave can stand for millennia to millions of years, and bats take advantage of that stability.
Consider one example from Arizona, where analysis of the mummified body of a spotted bat (Euderma maculatum) found by cavers in 1994 revealed it to be 10,400 years old. Spotted bats still wedge themselves into cracks of this cave today.
Subterranean features act as anchors on a landscape, Corbett said. Because of that, bats have a place to go back to again and again, for a long, long time.