The sound of them scrabbling through the walls and scratching at the floorboards is a sign that it's time to set out the traps. Humane traps, they are, little clear hard plastic containers with one way doors. Mouse goes in? Mouse can't get out. Simple and completely effective. Over the years I've caught a few, which I then take outside and release. Or perhaps I've just caught one stubborn one, who keeps getting recaught. Hard to say.
Last year in the spring, a horrid stench filled our washroom for a month. We looked all over for the source of it, and after a week or so, I finally found it. A forgotten trap had humanely trapped a mouse, who had then slowly starved to death, and then rotted.
It was gnarly, and reminded me to keep better track of our traps. I resolved to keep them clean and stowed in my workroom table.
So today, my son alerted me to the return of the little scritchy-scrabblers. I went to the drawer to retrieve the traps.
There, snug away in the drawer in one of the baitless, hidden traps, was the corpse of another mouse in an advanced stage of decay.
Perhaps they work too well.