The film is as much about the difficulties Native American people have adjusting to modern American life, the gap between those who want to adopt the methods of the White Man vs. those who want to preserve the old ways, becoming out-of-touch with and the death of their mythology and spiritual practices as well as their culture, and the natural order as it is just about killer bats.  Stuck in the middle is Nick Mancuso.  Starts off as a sort of mystery film then develops the horror aspects.  Would make a good double feature with THE LAST WAVE.