In the evenings as it gets dark there are bats flying all around my house, its fun to watch them dip and dive for the mosquitoes buzzing around. If memory serves they eat almost their body weight each night in bugs, if you have a lot of mosquitoes like I do that can be a big plus.
The realtor claimed he didn't know what they were, but the first night the family spent there, he figured out that they were to do battle with the bats that descended on, or woke up in, the abode.
That was in the 1970s.
They are definitely beneficial and worth having around.
I heard the die-off was due to a fungus that doesn’t let them hibernate properly and they starve to death in the winter because they can’t stay asleep.