We had the excitement of having one fly over us when we were photographing with the black light. We’re used to seeing the Little Browns, but this was a jaw dropper!! These are a threatened species in Wisconsin!!
Big Browns, like the Little Browns, nest in colonies. I seldom find them in our bat houses but they are known to be in barns, under bridges, or behind shutters on your house. They aren’t picky about where they hibernate as long as the temperature remains above freezing. In our northern climates, they migrate southerly until the winter is over.
While they eat most any insect, they are known to prefer beetles. Bats, in general, have few predators, but snakes, raccoons, and cats will eat them if the opportunity presents itself.
This Big Brown fact sheet will provide many more details.