something similar to vics prob,, some time ago, allthough i live in somewhat the country,,they dug up the feilds just down from me , to widen the road and build a" park and ride" all new drains etc, at that time there were rats come up our way becuase of this ,, but with my ferrets and my freinds managed to catch a few under various houses by blocking any outlets , then putting my ferrets in,, i run these regular under the lofts and under the house , i also throw the ferrets droppings under the loft etc,, seems to have worked ,, have had traps set,, poison down, but nothing touched,, and nothing in the traps for a good few months