I've had mouse droppings in my polebarn for the first 10 years I owned it. They nested in my vehicles, crapped all over. Tried the poison, some success, buy they kept coming in for the "food source". Tried the bucket with water with oats on top . . . . didn't work, just stunk up the barn. Tried the moth balls, dryer sheets, kinda kept them out of the vehicles, but they still had a field day in the barn. Tried traps to include the glue type, caught a few. Still lots of droppings . . . . This year, after a member here (I believe 64dart170, John)used a method to keep a bat out of his garage, I left a radio on 24/7. They hear the radio and will not come in. They must think there are humans in the barn. All winter, spring, and this summer I have had zero mouse turds. God luck with whatever you try!