Several years ago, my parents moved to the next province so my mom could get her degree. They were gone for two years and, as their house is across the street from the local trades campus, they rented out their home to students (yes - they thought this was a GOOD idea!).
Well, when they were coming back, it was up to my younger brother and I to send the students on their way, clean & make necessary repairs. I will not go into the disgusting state these supposedly adult people left another person's home in. Their parents should be ASHAMED to call them their children. I can't believe they weren't ashamed of themselves!
Obviously, they didn't leave any old little mouse problem. The entire house -attic, walls, floors, cupboards, basement....infested. My brother and I lived there for 6 weeks while we launched an all-out campaign! I researched the habits and tendencies and mice and found out two very important things.
1) mice are attracted to the smell of other mice - even the smell of DEAD mice. Unless you get rid of the smell (and this is a scent so delicate most humans cannot perceive it - not the mouse smell we all know and love) - others will follow!
2)a mouse's sense of smell is extremely delicate. Peppermint oil to a mouse is like setting off an airhorn in a human's ear - horrible and intolerable!
We ripped cupboards etc apart and cleaned. Then sprinkled the backs of the cupboards HEAVILY with Borax. Borax kills the scent of their presence so others don't follow.
We bought hinged-lidded tupperware containers and put all our groceries in them if the product was not in glass or metal. Boxes of cereal, crackers, etc - even things in plastic bags...those can be chewed through. The entire house has to be a no-snack-zone. Wash dishes immediately and put away (or keep dirty dishes in dishwasher). Half eaten candy bars etc were kept in a tightly lidded metal tin.
Under every sink, heater, etc - anywhere a pipe or wire or service comes into a room, the hole was sealed with something UNCHEWABLE. We used heavy wire mesh secured with construction staples or soapless steel wool. We also found their primary "runways" and created barriers. All runways got scrubbed and a liberal layer of Borax.
Cotton balls soaked in PURE peppermint oil were embedded in the steel wool or in our barriers. We also got these peppermint crystals from the Body Shop - they're meant to be dissolved in water for a foot soak. WOW! The hit of peppermint when we opened the jar was overwhelming! And that was just to a human! The crystals were a great medium for scattering like birdseed in the garage. We also opened every switchplate and outlet plate in the house in every room and sprinkled some into the walls.
It was hardcore for awhile, but once the mice were gone - they have never come back - and that was many years ago now. After about two months, we vaccumed up all the Borax.
It was kinda funny coming home to a minty house! But peppermint is not toxic and Borax is natural too. With a cat, you might want to spike it with cayenne so she doesn't want to eat it (can't imagine why a cat would eat Borax, but I had a cat that used to eat tinsel - LOL!)
I recently went through the same "crunch, crunch" aggravation with a raccoon in our underbelly - and this site was WONDERFUL! Hopefully, your mice will help you in the same way our raccoon helped us - in trying to get rid of it we discovered a HUGE array of problems under the mobile that we didn't even know about and thankfully were able to fix before winter!
Good Luck!
AT