I feel your pain. I battled rats through the winter. They tunneled under the platform where I kept the food in metal garbage cans. They created a tunnel that ran from one chicken coop to another. I tried pouring hot sauce into the tunnels, setting snap traps, moving everyone's food into raised feeders, opening the window so the dog would bark (sometimes, honestly, it was me and not the dog,) distributed peppermint essential oil-soaked cotton balls throughout the runs. I also removed all outdoor water at night.
I finally dug out all their tunnels, Installed even more hardware cloth everywhere and invested in an electronic rat trap. It cost $40 and I was miffed when it's first catch was a field mouse. But, eventually -- and it took weeks -- the trap and all my efforts paid off. No one eats off the ground anymore, unless it's clear across the driveway and I promise the ducks clean out their dish faster than a rat can move!!
I wish you the best in your fight. I was at wit's end before I got mine gone.
