During the recent ORCA excavations of the mound known as Outer Green Hill, in South Walls, among the remains of sheep, cattle, red deer, bird and fish bones recovered were the teeth and bones of ancient Orkney voles.
Why is this so important, given the fact that the bones of this subspecies of the common vole (Microtus arvalis orcadensis) have already been recovered (sometimes in large numbers) from many of the famous archaeological monuments of Orkney? What makes the South Walls finds unique is the fact that they have been found on one of several large islands in the county which now have no Orkney vole population.
The absence of common voles on mainland UK and Ireland, and their very strange distribution in Orkney, has been the subject of much debate and ongoing research into their likely introduction from western continental Europe by Neolithic farmers. The new South Walls evidence provides an exciting and important new twist to the ongoing story of the colonisation and dispersal history of Orkney voles.
A team of scientists at Durham and York Universities are using new genetic and morphometric techniques in order to establish the likely European origins of Orkney voles, as well as their colonisation history within the islands themselves. Dr Keith Dobney, director of the vole research group from Durham University, was part of the team uncovering the vole remains in South Walls.
He said: “The Outer Green Hill evidence suggests that Orkney voles were thriving on South Walls in the past, but that at some point they have subsequently become extinct on the island. The big question is why?
“Could this also be the case for some of the other islands where Orkney voles are not found today? The South Walls voles may lend some support to the idea that they may have been in Orkney longer than we think – perhaps from a time when Orkney was one large island, subsequently fragmented by rising sea-level into the archipelago we recognise today”
The vole remains from Outer Green Hill will be subjected to detailed genetic and morphometric analyses and then sent for C14 dating to be compared with the data already collected from the other islands.
When all this evidence is analysed over the next few months, there should be a much clearer picture of the history of Orkney’s most enigmatic small mammal.