Don Klipstein wrote:

I'd first try the mothballs.

Mothballs are toxic and not biodegradable. I would make a plan for
retrieving them.

Good point, putting them in a cloth bag on the end of a string so they can
be retrieved from under a building might be the way to go. Some folks swear
by pure oil of peppermint for getting rid of critters, but I've heard mixed
reports on that. One guy who put cotton balls soaked in the stuff down
gopher holes said the gophers just pushed the cotton balls out of their
burrows so he woke up in the morning to see all these cotton balls on the
lawn....