Mice are not man’s best friend. The House mouse like our houses because mice are opportunistic, and because life in the wild is usually more perilous for them than life with us. Heavy predation, weather and starvation are all great threats to the house mouse, especially in the wild. Exponential reproduction rates and the short period between birth and sexual maturity more than make up for high mortality rates.
House mice living out-of-doors have difficulty competing for food and territory with other species of mice. House mice are not particularly aggressive. Territories are maintained more by tacit agreement than by warfare. Nevertheless, two male mice caged together will usually not end well for one of them. Staying alive outside among the House mouse’s many predators poses another formidable problem. During certain parts of a year food can be very scarce in the wild. Since House mice do not hibernate they need the same quantity of food year round. Hence, they need to be near a larger food store than nature can usually provide. Who stores food better than humans? For all the above reasons House mice and humans are usually cohabitants of the same area. It is not because we smell nice to them or that we are such great companions.
As building dwellers House mice have developed many talents necessary for building life, especially a covert life. Their sense of balance, hearing and smell is remarkable. They see well but not in colour. They also swim well. In size they seldom reach 10 cm (4 in), counting the hairless, scaled tail length doubles their size. Their colour ranges from gray to brown. For the size of their heads their ears appear fairly large.
I have not read anything describing the House mouse as a human parasite, although it, at least partly, fits the description. The House mouse is not totally dependent upon humans, but we are a convenient, even if unwilling, host. They have been with us in the Western civilization since humans settled down to farming in the Fertile Crescent. There are known wild populations of House mice. On Gough Island in the South Atlantic where six human beings have maintained a weather station for South Africa for many years there are half a million House mice all over the fairly large island. However, in such cases the House mouse has evolved its behaviour to accommodate the environment. In their case on Gough Island the mice kill, by swarming, defenceless baby albatrosses by the thousands for their primary sustenance.
I am afraid that reading and writing about the House mouse has not convinced me to coexist peacefully with them in my dwelling. Even though the death of my daughter’s pet mouse years ago, of that nasty disease that makes them blind, was very sad for the whole family, I am as determined as ever to keep them out of my house.