Mice will absolutely squeeze under your door if they sense the smallest crumb on your floor.
Mice coming from next door.
You can also use a one door animal trap for rat mice and squirrel.
Poorly fitted windows can leave gaps around the edges.
If nothing else works or your neighbor is not willing to work on this problem you can call animal control.
Mice are lured inside by peanut butter or cheese and when the door closes behind them they can t get back out.
The most important thing that you can do to stop mice from getting under your door is to ensure you clean up thoroughly.
Store foods in glass or metal containers with tight lids and be certain to dispose of all.
Spring or glue traps are also effective but you risk catching wild animals with them if you place them outside.
This is also true if your house is old and your windows have not been replaced for some years.
To prevent the ingress of rodents you should first check.
All doors and windows must close properly.
Ensure that you check around each window and door to see if there are any holes small enough for mice to enter.
Mice proliferate quickly and populations may exceed 200 specimens within a matter of months.
Call pests controller.
Make sure that you sweep up thoroughly so you do not leave any food out that mice will be attracted to.
This trap protects and prevents injuries to animals.
Door window frame gaps fix any gaps around window and door frames.
While this has implications in terms of the spread of fire it will also mean that mice can easily travel from one property to the next.