Like leenia, I found that a cat needn't be a mouser in order to scare off the mice. When I had a mobile home in the woods I had mice. So I got a cat who seemed never to pay attention, but every night I left the kitchen cabinet doors open and I never found another sign of mice.

Speaking of feral cats, at another place there was a feral mother cat that neighbors said had a litter every year out by the railroad tracks. When I moved there, they were perhaps8 or 9 weeks old and wild as cougars.

I wanted a kitten so I started putting out food and little by little setting the dish closer to the back door. The mother never came close but the kittens couldn't resist and one day a kitten went into the kitchen. I closed the door- that ended up being a wonderful cat.