The Faroese house mouse was probably introduced accidentally from Britain by the Irish monks as early as the 6th century. It is the Western European house mouse (Mus domesticus) but has earlier been labelled as Mus musculus. This naming has also been used to name the subspecies which has evolved in the isolated island populations. The Nólsoy house mouse is a subspecies called (Mus musculus faroeensis) and the Mykines house mouse is also a subspecies called (Mus musculus mykinessiensis). However, a recent study, based on DNA-analyses, has shown that mice on the most remote islands (Hesti, Fugloy, Mykines and Nólsoy) are characterized as M. m. domesticus, whereas the mice on the better connected islands (Sandoy and in Torshavn) are mixed and have both M. m. musculus and M. m. domesticus genetic elements. Furthermore, the investigation indicated that the majority of the mice have their origins in south-western Norway, in agreement with human historical data, while the mice on the island of Sandoy may have arrived from the British Isles or from Denmark. The M. m. musculus genetic component appears to derive from recent immigrant mice from Denmark. The wood mouse or field mouse (Apodemus sylvaticus) was recorded on the Faroe Islands in the 17th century, but has not been recorded since. These recordings might have been mistaken. The house mouse is present on the islands Mykines, Streymoy, Fugloy, Hestur, Nólsoy and Sandoy. From time to time they have been located on Eysturoy, but they have never managed to establish themselves there due to the presence of the brown rat.
