One of the things to keep in mind is that when you bait a trap you are putting out an attractant for the “little guys” which can have the undesired affect of drawing them to your area. What we try to teach people to do is to use the rodents traits to work against them. In this case we position traps right alongside, and touching an object, such as a wall. They will walk along the wall for security (this is why you will seldon ever see a rodent crossing the center of a room or open space), then when they come to the trap, such as a Ketch-All, their natural curiosity takes over, and they just can’t help but to explore that nifty opening in the side of that metal box, after all, in their mind, that might be a good harborage for them, and that’s what their life is all about, or if its a pregnant female, she might think its a great place to have her litter, they enter, and soon become history. No bait required. When scared, they will leave a warning scent to alert other of the potential danger. This is why its important to wash the traps after a catch, if you don’t, its like putting a giant DO NOT ENTER - EXTERME DANGER sign at the opening for all other rodents to see. Remember, they read with their noses.
About those openings, you are absolutely right, if you can put a finger into the hole, a rodent can get through it. And lastly, the rule for determining the rodent population that there are ten for everyone that you see.
Tom Lehmann/The Dough Doctor