Rats tunneling under & living under garage?

Not sure if this will work but its cheap and worth a try: I used to work in the lawn & garden section at a farm store, and lots of the deer, rabbit, dog, small animal repellents (the natural ones anyway) contain cayenne pepper. A few of the other women I worked with said that straight cayenne pepper (crushed or ground) repels just as well (and is clearly much cheaper than a spray. You could try sprinkling a heavy dose of it around the holes and foundation of your house (or wherever they're digging for that matter). I mean if you think about it, if you're expecting mild dirt, etc and you dig into some burning cayenne pepper you won't likely make that mistake again. Like I said, I'm not sure that it works for rats, but its cheap and worth a shot! (I would look for a large jar of it considering the amount you'll want to use). After a few days sprinkle it again...the idea is the rats (or whatever animals you are trying to repel) learn this area is not one you want to mess with and eventually they leave it alone. I know it works on plants too (like for deer, rabbits, or dogs who like to get into your garden). Hope this helps!