Strobe light. I had squirrels in the crawl space above my attic - just the peak of the roof. Only accessible by one air vent next to a tree. I tried everything, moth balls, pepper spray. Then I bought a camping lantern that had "strobe" and stuck it up there. That got rid of them, and the mom took all of the babies with her - a complete evacuation.

I saw a you tube video while doing my research on how to get rid of them. This contractor wired this space they were getting into so the house could run strobe lights all of the time! But, I just had to do it once - I also replaced the vent cover, which is usually wood or plastic with one for an AC vent - which is metal.