I've had rats at this place since moving in 12 years ago. There are holes in the ground in my front yard, between the house and trees at the boundry. I thought they were living under the house, and digging tunnels under the foundations and coming up in the yard or under the trees, although the guys doing the insulation didn't mention anything. I would bait several times a year, run exhaust fumes down the holes, cats hang around the holes sometimes. I find young rats the cats have caught, or dead ones from bait. But still, fill the holes and new ones appear.
A few months ago we had a sewer blockage, the pumber came around and tried the plunger, but it was well blocked. We couldn't find the inspection port, so got the jet truck in. He blasted it clear, and then put his camera up...and then we saw the problem. Ceramic pipes, and the inspection port cap has fallen into the pipes and blocked the back flow. So now we knew where the inspection port was, so I dug a metre down in the front yard and found it. I didn't find any rats nests, but did find some voids. I think the rats were coming up the sewer pipes, through my inspection port and coming out my front yard. I've since secured the lid and backfilled. Sewer is clear....and no more rat holes.
