Orkney vole

Voles are small rodents that are relatives of lemmings and hamsters, but with a somewhat stouter body. In comparison with its family members, voles also have a longer, hairy tail; a slightly rounder head an smaller eyes and ears. They are sometimes known as meadow mice or field mice.

The Orkney vole (Microtus arvalis orcadensis) is a population of the common vole (Microtus arvalis) found only on the Orkney Islands, off the northern coast of Scotland. The common vole is absent from the rest of the British Isles.

The Orkney vole occurs on nine islands of the Orkney Islands: Orkney, Sanday, Westray, Rousay, South Ronaldsay, Burray, Eday, Shapinsay, and Stronsay.

As the Orkney vole has no natural enemies on these remote islands, they were able to grow massively. They are twice as heavy as continental voles,

The Orkney vole does not occur in mainland Britain, nor elsewhere in the British Isles. The current leading hypothesis for the development of this disjunct population is that voles were introduced to the Orkney archipelago by humans in Neolithic times, possibly concealed in animal fodder. DNA-analysis indicates transport by Neolithic humans from what is now Belgium.

The oldest known radiocarbon-dated fossil of the species in Orkney is 4,600 years old: this marks the latest possible date of introduction.

It was once hypothesized that the Orkney voles were a relict population, left behind when the land-bridge connecting Scotland and Orkney had disappeared, by the date that the more competitive Short-tailed field vole (Microtus agrestis) had reached Northern Scotland, though this theory has since been rejected based on paleontological, ecological, biological, and geological evidence.

A similar example of island gigantism is the Guernsey vole (Microtus arvalis sarniensis) that is living happily on Guernsey, one of the Channel Islands. It is (just) twenty per cent larger than its closest cousin, the European Common vole. Island farmers, simply ‘Mulots’, derived from Old French mulot, diminutive of mul, from Old Dutch muli ('moles'). Modern Dutch is still 'mol'.

A little sidenote: As so many of the islands in the region, the name 'Orkney' is derived from Old Norse. Vikings named it after the abundance of seals they encountered: orkn ('seal') and eyjar ('islands').