Way back - my husband's and my first house with a mortgage - we had our now RB kitty Jamara. Jamara thought field mice were her toys. We occasionally got field mice. She would bat them around, claws receded, until the poor little things had heart attacks. This usually happened on the basement steps. We had to watch where we walked!

SAS-you probably have field mice, so they won't GET very big, there might not actually be larger ones. Not that this makes you feel any better! You do need to find where they're coming in, though. Ours were coming in with the plumbing behind the refrigerator. We were young, Jamara was young, no one was that concerned and we moved before it became a real problem, so I'm sorry, I don't have a solution! Good luck!