How Many Sub Species Of Field Mice Are There In The Western Isles?

There are three extant sub species of field mouse to be found in the Western Isles. These are to be found on St Kilda, another on Mingulay and Berneray, and a third on the other islands that make up the Western Isles.

There is also a Hebridean sub species of house mouse. A second house mouse sub species also existed on St Kilda but died out after the islanders were evacuated to the mainland in 1930. St Kilda's only inhabitants today are a National Trust for Scotland warden and a small number of contractors who operate a radar tracking station for the Ministry of Defence.

The reason for this apparent abundance in mouse sub species in the Western Isles is due to the relative lack of numbers in the founding populations. The thinking is that with a smaller gene pool to start with, any traits or physical characteristics that were useful for survival were much faster to appear and dominate than would normally be the case. With little addition to local mouse populations from outside the islands, evolution occurred very rapidly, leading to the sub species we have today.

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