In my ongoing battle vs. the little tunneling monsters, I ran across this at Harbor Freight:
The Solar Powered Mole Chaser. I know what you're thinking. NO WAY! It'll never work. And you might be right. But at $9, I thought I'd give it a try. The box says it covers 6000 square feet. So that's one every 60 feet. I bought four to put around the house and the back yard.
That's about the cost of one box of Talparid.
Here's how it looks installed.
I have no idea how it will work, but I put one in the back yard right next to the most recent mine field of mole hills. The instructions say to let the battery charge for a day before turning them on.
When I powered them up, they make a somewhat high pitched noise about every 45 seconds or so. I can hear it, so it's not ultra sonic like a dog whistle or anything. They've been buzzing for about a day - I'll keep you informed on any new mole hills!
Wish me luck.