Mothball "ornaments"
I had problems with ground squirrels at a developed campground. Cost $250 to get the ducts cleaned in my truck, and it had sat for ONE day! They built one mutha of a nest inside the HVAC system: ciggie butts, weeds, seed hulls, trash dredged from previous campers’ slobbovitz littering and campfires.
Next time I went there, I didn’t want to let the little beasts run amok for the possibly 2 wks I’d be on the water. I bought cheap nylon pantyhose and cut the legs into tubes. Tied off one end of the tubes, dropped in a few mothballs, and then attached the “ornaments” under and around the truck and trailer, 8 packets of smelly repellence.
Returned after 9 days and was relieved to find NO nest invasion or other disturbance.
I use mothballs around the garage bldg and sheds at home, too. Mice and skunks hate them.
I’ve heard that bars of Irish Spring have the same effect but haven’t tried them.