There is a colony of bats that roosts near the far end of the prison, and most days at least one or two will be hanging out in the open either on the first or second floor.  They appear to be short-tailed fruit bats (Carollia sp.), but hard to tell without grabbing one.  These bats like caves and cave-like places, even if not totally dark.  A cement prison cell seems just cave-like enough that they have moved in.