Al:
To assist those who may find this thread and be wondering.........please allow me to post the link (and to those who might be wondering, no I don't have this product and have nothing to do with the company). I had to spend some time finding it again...
If you have rats living in tunnels under your run, that is almost the perfect setup for them. They can get food and water from the feeders and don't have far to go to get it. Just pop up and go to work, and inside an area protected from owls, dogs, cats, etc. to boot! Just about perfect.
So...
While you are working on a way to trap and kill some of these guys, may I suggest an additional step? If rats are in your run, most likely they are there for the feed, plus they probably have built tunnels beneath it.
If the infestation is that bad, perhaps consider capping the run surface...