BRITISH MAMMALS 
THE COMMON MOUSE OR HOUSE MOUSE. 
Mus musculus, Linnaeus. 
Plate 28. 
Smaller than the Wood Mouse, this species is easily distinguished 
from the other by its dull and more uniform colour, small beady eyes, 
and shorter ears and tail. The whiskers are also neither so long nor 
so plentiful. 
The head and body of the adult measure about 31 inches, the tail about 
3| inches. 
The colour of the fur in the upper parts is a dusky brownish grey, 
fading into grey on the sides and belly. The Common Mouse is subject to 
considerable variation of colour, those living an outdoor life away from 
houses having usually a more sandy hue than their indoor relations, while 
black, dark brown, white, or spotted examples are not uncommon. Some 
local varieties have been noticed on the Scottish Islands, the most distinct 
being the House Mouse of St. Kilda. 
As far as we know the Common Mouse had its origin in Asia, whence 
it spread into Europe in pre-historic times. 
It usually makes a home for itself in dwelling houses and will quietly 
enter new premises even before the building is completed. Breeding many 
times in the year and producing half-a-dozen young at a time, it increases 
enormously under favourable conditions, and like the Brown Rat soon 
becomes a plague if not kept within bounds. Great damage is done by 
mice in corn ricks, where they will often collect in hundreds. It is less 
nocturnal in its habits than the Wood Mouse and will often come out in 
daylight when in search of attractive food. 
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