Mink to root em out and terriers to catch em coming.
Fun as heck hunting rats.
Best hunting in the spring, while they are still burrowed up in the manure piles for warmth.
If you catch it right you'll get em all in about 4 hours...
If you wait too long and it gets warm enough, they all move into the barns and it's a whole lot tougher to get em out.