BRITISH MAMMALS 
THE ST. KILDA FIELD MOUSE. 
Mus sylvaticus hirtensis, Barrett-Hamilton. 
Plate 27. 
This is another very large sub-species, but less brightly coloured than 
the one last described. The largest of a number of specimens, obtained by 
Dr. Eagle Clarke on the St. Kilda group of islands in the Autumns of 19 10 
and 191 1, measured in length of head and body 129 millimetres, the tail 
100 millimetres, making the total length of the animal from nose to tip of 
tail about 9 inches. The following is from his description of this fine 
mouse in the Scottish Naturalist (June 1914), "The St. Kilda Field Mouse 
is confined to the main island Hirta, and to the adjacent uninhabited isles of 
Soay and Dun. It is most abundant where coarse grass prevails, but is to 
be found almost everywhere — in the crofted area, in the neighbourhood of 
the houses, on the faces of the cliffs, and on the sides and hill-tops ; finding 
congenial retreats in the rough stone-built ' cleits ' (which are such a feature 
in the St. Kilda landscape) and in the walls surrounding the crofts ". . . . 
" That the underparts of hirtensis are heavily washed with yellowish brown 
has hitherto been deemed an important characteristic of the species. This 
is not the case, however, for in the majority of adult specimens, and many of 
the immature ones, the throat, chest, and abdomen are white, and only 
washed with brown along the narrow medium ventral line. As a result, the 
demarcation between the peppery reddish-brown upper, and the pale under 
surface is pronounced in most examples, and renders the species very similar 
to the familiar Long-tailed Field Mouse {Apodemus sylvaticus). About 
one-third of the adults and the majority of the younger specimens have the 
under surface more or less strongly washed with yellowish brown." 
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