As well as all the other normal rodents that can destroy your beautiful vintage trailer.

Step 1)  Go to Dollar store
Step 2)  Buy a box of drier sheets.
Step 3)  Return to trailer
Step 4)  Place the drier sheets in all those little nooks and crannies (especially the crannies).  In drawers and cabinets, under the bed and dinette seats, etc and the wheel wells and storage compartments too.
Step 5)  Have a cocktail and pat yourself on the back for rodent proofing your pride and joy.

It really is THAT simple folks.  My parents have been storing food (not properly either I might add) in their garage for years and have never have a problem.  Just change them out once or twice a year, especially when you close it up for the off season, and you'll be rodent free.

Mothballs work too, but the drier sheets smell nicer.