We’re RVers & volunteer in Texas State Parks where this has been a problem for some. I have some rodent countermeasures that have worked for me. Go to a Tractor Supply store & but two products. One is Repelz-All which is granules that come in a jug. Sprinkle this on the ground where your vehicle will be parked. It smells like fresh dug dirt. Reapply it every few weeks. The other product is Fresh Cab which is a potpourri-like product that repels rodents. It is in little bags that you can zip tie under the hood. We put “Just One Bite” rat & mouse poison in the basement storage if our 5th wheel. They will eat it, but they won’t die until they go outside & drink water. That way you won’t have smelly little corpses inside your vehicles. It’s not available anywhere except Anazon that Im aware of. We haven’t actually had any critters in our trailer, just doing everything we can.
Ive never tried this, but I hear that essential oils such as peppermint oil do a good job as well.
Good luck!