A house mouse nibbling on a biscuit. Photograph by David Chapman
In winter a couple of years ago, our neighbours pulled down their garage in order to make an extension to their house. The garage had stood for decades and had lots of bits and pieces stored in it, many of which had lain undisturbed for a long time. Unbeknown to me, or presumably my neighbours, the garage had also been home to quite a large population of house mice. How do I know? Well shortly after the garage was pulled down I started to find house mice in my workshop which is nearby.
My workshop is attractive to wildlife. I have often seen wrens in there looking for insects; in winter I see peacock butterflies hibernating on the walls and throughout the year I regularly spot wood mice running along the window ledges. Wood mice are distinctive creatures with light brown fur on their backs and white fur underneath, they have long tails and are very attractive creatures.
Prior to the winter in question I hadn't seen house mice on our property for many years and the first sign of their invasion was their distinctive musty smell. Getting into my draughty old workshop wasn't a problem for them since house mice can squeeze through the tiniest of holes, it is said that they can get through a 6mm gap, that's the width of a biro.
House mice are not as attractive as wood mice, they are fairly mono-tone with grey-brown fur and a slightly unkempt appearance. The house mouse is common in Britain but their preferred domain is around humans so they are not particularly numerous in the countryside where their country cousin, the wood mouse is boss. It is thought that house mice were originally only found in Asia but through the activities of humans over the centuries they have now colonised the entire world with the exception of tropical Africa.
House mice don’t just like to have humans close by, they actually need us. One example which goes some way to proving this point was seen on the remote island of St Kilda off the coast of the Hebrides. This remote island was once occupied by both humans and house mice but when human habitation ceased the house mouse soon became extinct there.
House mice will eat just about anything and will even gnaw at things which are inedible, such as electric cables for which they can become a pest. They are fairly adaptable but can’t cope with competition from other mice so a good population of wood mice will usually out-compete house mice. That was how the balance in my workshop used to be maintained, fortunately by the following spring the house mice had all gone again, presumably replaced once more by wood mice.