I've been putting traps and poison in our roof trying to get all the rats that live up there. Not really sure how they're getting in. One of them was huge, tip to nose about the length from my elbow to my finger tips.
I don't know how but they seem to manage to eat the bait off the traps without setting them off, or sometimes setting them off but not getting caught. I have 1 big steel trap, another big plastic one and a little tiny old fashioned wood and wire type one. One of the rats looked like he managed to eat the bait off the two big traps then get caught by the little trap that I hadn't bothered baiting, just set it and put it down.