I would have bet on the fact that our coop and run were as secure as Fort Knox. We learned by trial and error what kept what out. We reinforced the sides with 1/2" hardware cloth to keep our Pyrenees from breaking through. We covered the top with chicken wire to keep the hawks and owls out. We ran hardware cloth up under the deck boards to keep out the squirrels and we put chicken wire out two feet around the outer perimeter and two feet on the inside of the perimeter to keep anything from digging in and out. We put a corrugated metal roof on the coop. What we underestimated was the persistence of rats. Our coop is towards the rear of our property and borders a wooded area. A few weeks ago the chickens started sleeping outside rather than going in their coop at night. We couldn't figure it out - they had always slept in their coop - loved their coop and it was pretty darn cold and wet outside so we figured something was wrong - just didn't know what it could be. Well my husband and I went out with our flashlight and decided we would pick them up, put them in and close the door. That's when we saw them - rats. I went to Tractor Supply and bought one of those $50 traps that when they enter it zaps them - it's been days and no rats. I bought one of those $15.00 ones that has the bait enclosed - no rats. I bought a couple of tomcat rat traps and we baited those - no rats. I bought decon rat bait and the best I can tell it is undisturbed (it is inside the storage house where we keep the food) . We bought galvanized cans and put in all the feed and treats. I thought my dog was digging under the run to get at the chickens - instead he had sniffed out a rat tunnel and had them on the run. He has managed to sniff out and kill a couple but it did let us know where the tunnel was so today I filled that entire area with a couple of sacks of quick crete. I locked the chickens up in their coop in order to let it dry and searched out any other places where it appears they were tunneling far enough under the hardware cloth to come in. So far with all we have spent on traps and baits nothing - only the dog has done any damage. I had seen where someone had posted something about the expanding foam that was rodent proof - does anyone know where I can get that and what it is called. I want to spray the roof line where the corrugated metal has the ridges to make sure they don't go in the coop. Next question - what is the best rat bait - it seems that my traps and such are not getting the job done - do the rat blocks work? I can only put out the decon in the enclosed house where the food is kept. I don't want my dog getting into it. Our uncle lives on the other side of the wooded area and he has cats that he feeds each evening. He now has possums and coons coming for the cat food. I am going to buy a couple of the live traps and try and catch those - putting them in the woods between our houses - what is best to bait those traps with? I figure it won't be long before they start trying their luck getting in the coop and run.