Rodent Deterrent?

I opened up my trailer today and found a live mouse in the cockpit.
Naturally, there was a lot of mouse poop in the cockpit and in the
trailer. I had made at least one mistake of leaving a good supply of
crackers and granola bars in the cockpit and up front in the trailer.
Little bugger had a great home, complete with large food supply.

Tomorrow, the glider will get its annual condition inspection and I'll
be looking closely at tubing and wiring. I don't know if I'll have a
chance to do a leak check tomorrow on the system, but I will soon. My
quick look today didn't show any teeth marks.

Does anyone know a deterrent to rodents? How can I keep them out of
the trailer? The trailer stays parked outside, unfortunately. Would
moth balls work if placed in both the trailer and the cockpit?

Thanks,

Ray Lovinggood
Carrboro, North Carolina, USA