If you have 120 volt power hooked up, you can use a device called "Pest-A-Cator" available from amazon for about $15.
Places an ultrasonic vibration on the wiring loop that resonates in the sinus cavity of rodents (in Florida that means rats and squirrels).
I know it sounds like VooDoo, but ... IT WORKS!
We had continuing problems with grove rats and/or Avacado eating squirrels until I installed one unit in the trailer (stored in the back yard) and one in the shed. No sign of any entry since.
It doesn't bother the dog and people cannot hear it, but IT WORKS!
If you should have rat odors in the trailer, a chemical called "Rat Sorb" will clear it up. (Don't ask.)
I have no interest in either company, just a satisfied customer.
Good luck.