The St Kilda House Mouse (Mus musculus muralis) was a subspecies

Subspecies

Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

 of the house mouse

House mouse

The house mouse is a small rodent, a mouse, one of the most numerous species of the genus Mus.As a wild animal the house mouse mainly lives associated with humans, causing damage to crops and stored food....

 found only on the islands of the St Kilda

St Kilda, Scotland

St Kilda is an isolated archipelago west-northwest of North Uist in the North Atlantic Ocean. It contains the westernmost islands of the Outer Hebrides of Scotland. The largest island is Hirta, whose sea cliffs are the highest in the United Kingdom and three other islands , were also used for...

 archipelago

Archipelago

An archipelago , sometimes called an island group, is a chain or cluster of islands. The word archipelago is derived from the Greek ἄρχι- – arkhi- and πέλαγος – pélagos through the Italian arcipelago...

 of northwest Scotland

Scotland

Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

.

It is uncertain when they first arrived on the islands, but it is possible that they unwittingly were transported there during the Norse period

Norsemen

Norsemen is used to refer to the group of people as a whole who spoke what is now called the Old Norse language belonging to the North Germanic branch of Indo-European languages, especially Norwegian, Icelandic, Faroese, Swedish and Danish in their earlier forms.The meaning of Norseman was "people...

. Isolated on the islands, the St Kilda House Mouse diverged from relatives, it became larger than the mainland varieties, although it had a number of traits in common with a subspecies found on Mykines in the Faroe Islands

Faroe Islands

The Faroe Islands are an island group situated between the Norwegian Sea and the North Atlantic Ocean, approximately halfway between Scotland and Iceland. The Faroe Islands are a self-governing territory within the Kingdom of Denmark, along with Denmark proper and Greenland...

, Mus musculus mykinessiensis.

When the last St Kildans were evacuated in 1930, the endemic house mouse became extinct very quickly, as it was associated strictly with human settlement. Some specimens exist in museums. The St Kilda Field Mouse

St Kilda Field Mouse

The St Kilda Field Mouse is a subspecies of wood mouse endemic to the Scottish isles of St Kilda. It is generally twice as heavy as mainland field mice and has longer hair and a longer tail. It is mostly grey in colour and, though hard to find, very common.It is not to be confused with the St...

(Apodemus sylvaticus hirtensis) is still present.

Sources

• Harrisson, T. H. and J. A. Moy-Thomas. 1933. The Mice of St Kilda, with Especial Reference to Their Prospects of Extinction and Present Status. The Journal of Animal Ecology, 2: 109-115.
• Musser, G. G. and M. D. Carleton. 2005. Superfamily Muroidea. Pp. 894-1531 in Mammal Species of the World a Taxonomic and Geographic Reference. D. E. Wilson and D. M. Reeder eds. Johns Hopkins University Press, Baltimore.