... found a bar of Fells Naptha laundry soap. The mice had eaten almost half the bar! ... More like if they are hungry enough and they can digest it they'll eat anything!
Tell me about it! I finally got a game camera to see what was waking us up. In the night there's a parade of critters across the deck - deer, skunk, raccoon family, possum, bobcat, fox. Under the house, all those except deer but then add rat and feral cat.
Under the house is worst. Raccoons scrape the floor joists with their claws - apparently eating bugs from spiderwebs - and we were nearly sure that racket was something climbing up inside the wall - behind our bed. Loud!
I read that Irish Spring soap repels deer and others. I put a bar on a pole and coated some of those joists, plus all the entry points to this no-perimeter-foundation old farmhouse. No effect at all. And the remainder of the bar was half eaten.
The only thing that has helped is lights I can turn on remotely on the deck and under the house. Light plus stomping on the floor makes them stop and look around, but not run away. I'm still looking for solutions.