A mouse in the house- help please

They can get through a hole the width of a small finger. We used to get them in a previous house because there was a nice little gap in between the original part of the [old] house and the extension. They'd end up in the leccy cupboard, but it also meant they travelled along the space in the bedroom walls to get there, and we could hear them through the night.
A mix of various things, traps etc, including that expanding foam in the cupboard, helped, but it's hard to prevent them coming in in the first place without a fair bit of effort.
We have plenty here, but they never get in the house. Too busy eating the bird food in the cages, as they have a nice little route up to those.

 

Weather you use humane or inhumane traps as Nigel says they can’t resist a bit of Christmas cake.
I am just the same .

 

An update- we've had a bit of an adventure

Firstly, our cute little mousie-pousie turned out to be a rat. A bit hard to mis- identify when the said Mrs Rat happily crosses the terrace several times a day, stopping to sniff a corner here and there and then continuing under the fence to the neighbours' side.

So we upgraded to humane rat traps and organic peanut butter, promptly accidentally dropping them into unreachable places when checking them and resorted to banging the walls when the scuttering started.

Then something changed some weeks ago, it could be related to the pipework carried out a block away by the water company. The rat started visiting inside the house

I called in the council Rat Man (Paul) who was very nice and knowledgeable and gave excellent advise, identifying probable entry points and recommended to get a handyman to come in to concrete them up. (He also shared a lot of gossip about the rather unconventional neighbours on the other side )

This week the rat started visiting neighbours as well, so now Paul The Ratman just pops in a couple of times a week to give the latest.

Our handyman came in today and did a great job in filling in the entry holes outside by the pipe, confirmed that there are no holes under the slabs against the extension wall, and filled in the humongous Rat Highway under the kitchen sink. The hole was big enough for cats, or a slim leopard

Now everything is filled with rolled up metal mesh and sealed with copious amounts of concrete.

We'll wait and see what Mrs Rat will do now when the usual places are blocked- most likely we'll see some investigation activity.

The material damage from the indoor visits (of the rat, not Paul or Handyman) is limited to a pinched doormat stuffed behind the pantry fridge, decoratively nibbled old towel that was waiting to be washed, and a roll of bin liners with new airing holes. Cables are untouched.

 

I assume the holes were sealed with Mrs Rat on the outside @Selleri?

 

Well, that's the thing- Mrs Rat is not exactly the kind of person with whom you whip out calendars and align on suitable slot for the works.

We'll just have to wait and see and deal with things as they come along.

So far it's very quiet. Very.

 

I once opened the bonnet of my car, in the garage, and found several apples balanced in nooks and crannies around the engine. Rats are very resourseful and are good at solving problems. In another garden I watched a rat climb onto the top of a dustbin next to a shed, up the side of the wooden shed, in through an open window to get to a bin of rabbit food. In this garden I watched a rat climb the post of a wooden bird table, reach out around the edge, haul itself onto the top, stuff itself with bird food, go to the edge, hang on by its back toenails upside down, until fully extended, then drop down to the ground. It was back a few minutes later to repeat the exercise.