I know they are around, the stones from fallen Plums get stored in little corners. Plum Stones with holes nibbled in are strewn here and there. When I sow Broad Beans in trays in my Greenhouse a small percentage vanish overnight leaving a small hole in the compost.
Early this year a tunnel appeared (mouse size) among some Rhubarb, running some 2 feet under the Greenhouse wall to emerge inside. I tolerate a little theft, they have their place in nature.
In the Autumn they often search for warmer Winter quarters and I tend to set a trap in my Garage baited with Belgian Dark Chocolate. It is a really good bait, hard, it never goes off, the same Little Finger Nail size piece I lost the other day was at least 6 years old and had tempted some dozen mice to their demise.
Come this time of year I picture a family of Beatrix Potter Mice, bonnets, suitcases and all, coming down the road from the country looking for a cosy spot. Why do they pass a few other houses and cross a road before Papa puts down his cases looks down my drive and says 'how about this one dear'?
Two weeks ago I noted soil coming from under a fence post which is screwed to my neighbours garage wall so doesn't quite reach the ground. I suspected Mouse activity, there is a difference in levels so they would have a tunnel system under paving.
I took a palm size stone and rammed it in the hole with a steel rod before we went off for a week.
Upon our return the stone was out and much more tunnelling spoil was spread around. This is just outside my Conservatory door too close for comfort. Here Beatrix Potter pictures end.
I set my trap near, covered by an upturned tub and a rock to stop it blowing away. Next morning I lost my Belgian Chocolate, there was a Field Mouse in the trap. French Dark Chocolate works just as well, day 2 another Mouse, same knob of choccy. Day 3, 4, 5, the same until this morning when I saw as I opened the door, a mouse scuttle from under the tub back into the tunnel.
So no catch last night? yes there was and he had been eaten starting at the eye. A quick check on Google and it seems Cannibalism is common in Mice. They don't kill each other for food. A dead Field Mouse that died in a fight, or a trap it seems, may well be eaten starting with the brain.

................"You know, if you you die I shall eat your brain"...............
So now that is 7 I have seen, I wonder how many there are, too many definitely, and too close for comfort. Sad but gardening is like that at times.