St Kilda field mouse

{{Subspeciesbox

| name = St Kilda field mouse

| image = St Kilda field mouse (Apodemus sylvaticus hirtensis).png

| image_caption =

| genus = Apodemus

| species = sylvaticus

| subspecies = hirtensis

| trinomial = Apodemus sylvaticus hirtensis

| trinomial_authority = (Barrett-Hamilton, 1899)

}}

The St Kilda field mouse (Apodemus sylvaticus hirtensis) is a subspecies of the wood mouse that is endemic to the Scottish archipelago of St Kilda, the island {{Convert|40|mi|km|abbr=out}} west of Benbecula in the Outer Hebrides, and {{convert|100|mi|km}} from mainland Scotland.{{Cite web|url=http://www.kilda.org.uk/weekildaguide/index.htm|title=St Kilda Guide|access-date=2013-05-20}} Unique to the islands, the mouse is believed to have arrived on the boats of Viking settlers more than a millennium ago. It is not to be confused with the St Kilda house mouse (Mus musculus muralis), a subspecies of the house mouse which is now extinct.{{Cite web|publisher=BBC|url=https://www.bbc.co.uk/news/uk-scotland-highlands-islands-11168757|access-date=2020-03-02|title=St Kilda's 'super-sized' field mice studied|date=2010-09-03}}{{Cite news|url=https://www.bbc.co.uk/news/uk-scotland-highlands-islands-11101243|title=The new residents of St Kilda archipelago|date=28 August 2010|access-date=16 May 2013|publisher=BBC News}}

The last remaining human inhabitants of St Kilda abandoned the islands on 29 August 1930. Thereafter the mice that survived, even those occupying houses abandoned by the St Kildans, were field mice that had moved into the houses from the hills. The islands' house mice could not survive the harsh conditions for more than two years after the archipelago was abandoned by its human population. The islands currently have temporary human habitations. While field mice are widespread on Hirta, their concentration is more pronounced in the old village areas where holes provide access into buildings.{{cite book|title=Scottish Field|url=https://books.google.com/books?id=nFc-AQAAIAAJ|access-date=16 May 2013|year=1980|publisher=Holmes McDougall|page=23}} Though rarely observed by casual visitors, the mouse is common and is present in every part of the habitat, from the harbour to the high point.

Description

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, with a mass of between {{convert|50|g|oz}} and {{convert|70|g|oz}}, and has longer hair and a longer tail. The evolution of a larger size has been credited to a lack of predators in its island habitat,{{Cite web|url=http://collections.glasgowmuseums.com/starobject.html?oid=325390|access-date=2013-05-15|title=St Kilda fieldmouse (Apodemus sylvaticus hirtensis)|publisher=Glasgowmuseums.com}} which allows the mice to grow larger to preserve heat and increase fat storage. The mouse can reach a maximum length of about {{convert|17|cm|in}}. It is found across the main island, Hirta, especially in the remains of human settlements, as well as on the island of Dùn. It is not found on Boreray. Studies of the fur of the mice have recorded the flea species Ctenophthalmus nobilis, and Nosopsyllus fasciatus on the mouse as well as the mite Typhloceras poppei. Studies of the intestines have observed the nematode Tictularia cristata and the cestode Hymenolepsis diminuta.{{cite book|title=Proceedings of the Zoological Society of London|url=https://books.google.com/books?id=RrgmAQAAIAAJ|access-date=16 May 2013|year=1959|publisher=Longmans, Greens|page=64}}

Diet

The mouse is an opportunistic omnivore. Its diet includes insects, snails, seeds, and moss, as well as human litter and animal carcasses. With only one other naturalised mammal, the Soay sheep, which eats grasses and herbs, the St Kilda field mouse faces little competition for food on the islands.{{cite web|title=St Kilda mouse research starts|url=http://www.ed.ac.uk/schools-departments/biology/evolutionary-biology/news-events/archive?id=164&cw_xml=ieb_archive.php|publisher=The University of Edinburgh, Institute of Evolutionary Biology|access-date=16 May 2013|date=29 October 2009}}

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. The taxon was first described in 1899 by Gerald Edwin Hamilton Barrett-Hamilton{{cite book|last1=Boyd|first1=John Morton|last2=Boyd|first2=Ian L.|title=The Hebrides: a natural history|url=https://books.google.com/books?id=GasfAQAAIAAJ|access-date=16 May 2013|year=1990|publisher=Collins|page=307|isbn=9780002198844}} 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.{{Cite web|url=http://www.kilda.org.uk/mice-wrens.htm#.UZRxVMo2XLk|title= Mice and Wrens|access-date=16 May 2013|publisher= Kilda Organization}}{{Cite web|archive-url= https://web.archive.org/web/20160305055800/http://www.kilda.org.uk/kildanomdoc/level3p13.htm|archive-date= 2016-03-05|url=http://www.kilda.org.uk/kildanomdoc/level3p13.htm|url-status= dead|access-date=2020-03-02|title=Land Mammals|publisher=Kilda Organization}}

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.{{Cite journal|jstor=3564987|title=The St. Kilda Field Mouse (Apodemus sylvaticus hirtensis Barrett-Hamilton), Population in the Village Area, Hirta, May 1955|pages=110–116|last=Boyd|first=J. Morton|journal=Oikos|volume=7|issue=1|doi=10.2307/3564987|year=1956}}

References

Category:Apodemus

Category:Rodents of Europe

Category:Fauna of St Kilda, Scotland

Category:Endemic fauna of Scotland

Category:Endemic biota of the Scottish islands

Category:Mammals described in 1899

Category:Taxa named by Gerald Edwin Hamilton Barrett-Hamilton