I have a timer for my chicken house lights, and one day the lights didn't come on. I replaced the bulbs, still no lights. Checked the circuit breaker, it was tripped. I reset it, but when the lights came on they tripped the breaker again. I dropped the ceiling panels in the hen house and found that there were sections of the wiring where all of the insulation was chewed off and one section had a dead mouse on it. I am lucky that the building didn't burn down!
There are traps that you can make, even as simple as getting something like an empty plastic bottle (soda, water, etc...) and putting a bit of peanut butter in the bottom. Tie a string around the top and attach it to something, then put the bottle on the edge of a shelf or table or something with at least half sticking out from the edge. Mouse goes in for the peanut butter, gets to the part of the bottle hanging out, tips the bottle off and the string keeps it from falling all of the way down. There are different varieties of mice in the wild, they don't all look like common field mice. Mice are actually curious.
What creeped me out was going in to take care of my turkeys (the only building I have that the cats can't get into) and having about a dozen rats staring at me. Many late nights there with a flashlight and a pellet gun... DH and DS never went out, maybe they are scared of rats? Between me, the cats, and the weather that flooded the building (had to move the turkeys out), I think they are gone... ugh!