A mouse can fit through a hole big enough to accommodate its skull, which is pretty small.
I went around my foundation and used an expanding foam spray to seal up any holes. Definitely worth your time once the spring thaw comes.
Or a snake. Friend of a friend had mice, and a pet snake. Snake got loose and crawled into the walls. Stayed there for about a month, then come slithering out none the worse for wear. Mouse problem was evidently solved - doubt the snake ate them all, more likely they came to the group decision that He Who Crawls Between The Walls is a vengeful god and it was time to infest the neighbors instead.
And they have been known to gnaw at the electrics inside, get electrocuted, and then create a foul burning stench every time the cooker is used, until it is removed for replacement, at which point the mouse briquette can barely be identified. Ick.
Yep, I’ve often heard it said that a mouse can fit through any hole which can accommodate a Bic ball-point. I have no idea how accurate this is, but it’s probably not far off.
**Nanoda ** - bear in mind that if a wall has a hole in the inside and outside, connected by a long winding narrow space (or with some burrowable insulation between), it will not necessarily be obvious to anyone but the mice that there is a mouse highway leading into your home.
Again, no cite but I believe this is the explanation for your dust & fluff - mice corpses are small and near a constant source of dry heat with good airflow will probably turn into a furry strip of beef jerky pretty fast.
I have 8 or so glue traps as “monitoring devices” in my attic, basement, utility room, etc. Initially I caught one. Haven’t caught one nor seen evidence of rodents, but I like the idea of constant surveillance.
(to those who say glue traps are inhumane, I agree but use them anyway.)
For those using snap type traps, use peanut butter or Cheese dip… something that cant be scurried off with.
The early bird may get the worm, but the second mouse gets the cheese!!!