St Kilda field mouse

The mouse has black eyes, small peaked ears, and is fairly uniform in colour: mainly brown, with a lighter shade of fur on its underside. It is generally twice as heavy as field mice found on the mainland, which allows the mice to grow larger to preserve heat and increase fat storage. ==Diet==

The mouse is an opportunistic omnivore. Its diet includes insects, snails, seeds, and moss, as well as human litter and animal carcasses. ==History==

Unique to the islands, the ancestors of the St Kilda's field mouse are believed to have arrived on the ships of Viking settlers. as the separate species Apodemus hirtensis. A year later in a specific review of mouse species the taxon was reclassified as a subspecies of the wood mouse Apodemus sylvaticus. Studies of the mouse populations on the islands were carried out in 1931, 1939 and 1955. These studies documented the rapid extinction of the endemic house mouse subspecies (which was dependent for its survival on grain and other commodities used by the islands' human inhabitants), and its subsequent replacement by the field mouse, through a process of niche expansion. ==References==