Thanks, everyone, for all the great information.
I've noticed in reading the links that some methods work for some people and not for others. I wonder if it depends on geographic location and species of mouse. We are in western Canada at the moment, and the species we are having a problem with is deer mice--prime carriers of hanta virus and therefore very dangerous. I've spent the day decontaminating our motorhome. Mask, gloves, coveralls, disinfectant, this was a huge job. We hadn't realized mice would be able to gain entry, we thought the coach was more secure than that, so we hadn't taken our usual steps to prevent it. (Gain fabric softener sheets and mothballs worked without fail in our fifth wheel. We never left traps in during winter storage because we didn't want anything fermenting in there.)
Now we're back to the Gain sheets. Electronic devices are emitting a sound to irritate rodents. I've placed a couple of mothballs just in front of the driver's seat near the pedals, I think this is where the critters gained entry. While the motorhome is parked here, I will also leave moth balls on top of the tires, although I suspect maybe sheets of tin foil left on top might work as well, as this is the only way the mice could have reached anything underneath to find a way in, climbing up the tires. I looked underneath today, and there are no openings into the basement compartments. The plumbing compartment was closed, and even if the electrical cord is out (which it wasn't when the mice got in), there's no way into the motorhome through there.
We'll be storing the RV at a place in a city in Nevada later this winter and I'm wondering what the mice there dislike, or if the hanta carrying mice are present in the cities. I don't want any, though, regardless of species.
I'm interested in the products by Earthkind (thanks, Sully2). I think DH might prefer the smell of these as well over the Gain sheets. 🙂 I find these fabric softener sheets take on a smell that gets a little less than pleasant after a while.
I am also going to pick up a bottle of peppermint oil and some cottonballs.