What's Digging These Holes?

The weather is finally cooling off a few degrees and I got to spend a couple hours in the yard. I know I'm odd; but I actually like pulling weeds; and there's no shortage of them! I especially get a lot of satisfaction out of pulling out garlands of Virginia Creeper which I've never been able to eradicate.

Anyway, the back corner of the yard around the herb garden has been dug up sporadically for at least a year. What critter does this, anyway? I suspect raccoons, since two of them tried to make a hole in our roof last year and cost us $300 in repairs. After that episode, we greased the pipe they were climbing with Vaseline. It was pretty funny to see the claw marks sliding down the pipe the next day. The holes are about 5" deep and come to a point. I would dearly love to know how to encourage these unwanted visitors to go away and never come back. What we really need is to borrow a big dog!