I once had a serious mouse infestation. As in 37 mice trapped inside a small house over a 6-month period, plus more caught by a borrowed cat. It was a mouse city. My landlord had stored a bunch of furniture in one of the storage/work areas attached to the house, stacked to the ceiling. The mice treated that like a series of skyscrapers, they climbed and nested in that furniture from the floor to seven feet high throughout the room. They even had a subway system under the slab that formed the dining room floor. The subway system led to various electrical and plumbing penetrations that allowed access inside every wall in the house, especially the room I lived in, plus access to the inside of the house through the plumbing into the kitchen. My roommate had a dog, and the perpetual supply of dog food fed an infinite number of mice, with desert perpetually available in the kitchen. Even after 37+ mice there were still at least a dozen. Previously I thought mice were sorta cute, not any more! Round the clock stench, squeaking, and scratching! Eventually I learned that for a serious mouse problem traps are not the ultimate solution; you have to physically block their access to both food and your house to keep them away. Spray foam or any material softer than teeth is ineffective. Cats are merely population control, not eradication.
Eventually I came up with only 3 ways to stop mice:
1. Concrete. I poured several sacks at strategic locations.
2. Stainless steel wool. If properly secured it can't be dragged away, and it can't be chewed through.
3. 1/4" galvanized or stainless steel hardware cloth (available at any home supply/hardware store), stapled with staple gun or small nails. Too small to pass through, too hard to gnaw though.
Secure stainless steel wool in all holes larger than a dime, and staple the 1/4" mesh over the top. Pour concrete around locations where they might be burrowing. Eat that mice!!!!!
