What creature is this? "Worldwide distribution greater than any other mammal excepting Man." It is the common house mouse - mus musculus, according to The Collins Field Guide to Mammals of Britain and Europe, and the book was dipped into in the hope that it might be in the remit of the authors to tell us how to keep mice at bay or to discourage them, for we are now heading into the Months of the Mouse. Are these invaders, who somehow come in behind the drawers in the kitchen and chew through your plastic bags of pasta, or romp around an unoccupied bedroom, even distributing their dirt behind the pillows, are they house mice that have come back from their summer outings in the fields and ditches, or are they field or wood mice that live and breed in the area around, and just come in from the cold from autumn to spring? They hope, for not many of them survive the deadly lure of melted chocolate as bait on a trap, which they can't snatch away without bringing the executioner's chop down on themselves.
It would be preferable to keep them out in the first place - by deterring them with some odour (cat is not feasible in this case). Away back it was read somewhere that the green leaves of walnut trees were a sure repellent. Fortunately, a big tree was available, and drawers and corners and the space underneath bookcases and suchlike were stuffed with the greenery. To no avail. Maybe it even pleased them - raw material for the nest, though, on the rare occasions that you come across one in the boiler room, it is made from chewed-up newspaper.
For it is written in this book that mus musculus - if that is what this intruder is - may, if food is sufficient, produce five to 10 litters of four to eight young per year. This Collins book mentions 17 varieties of mouse worldwide; Fairley in his Irish Beast Book tells of the term bean mouse given to the field mouse, for they have been known to carry off every single bean or pea planted in a garden near Belfast. Thompson, the Northern naturalist, summed up, enigmatically: "Traps made of a single brick were successfully used for their destruction." Then there was the singing mouse. That is for another day.