We recently put our 5th wheel in storage on a farm field in southern British Columbia. The owner warned us that mice were a problem, so we set out four trays of blue poison mouse pellets. A week lat...
Hardware stores, garden centers, etc usually have them. Simple black boxes designed to hold the bait.. allowing mice and rats into them, but larger animals can't get to the bait.
I prefer Ramik, or better yet One Bite, but you can use the Tomcat bait boxes with whatever bait you want.