There are relatively few species of land mammal in Orkney. The wood mouse, brown rat and pygmy shrew are found widely. Rabbits are numerous and can be found in most areas, whilst the Mainland is notable for its population of brown hares. A speciality of the hills of Hoy is the mountain hare, which has a coat that turns white in winter.
The most unusual mammal is the Orkney vole. This chunky little rodent can be found all over the Mainland and South Ronaldsay, but it is missing from some of the islands such as Hoy and Flotta. The Orkney vole - Microtus arvalis orcadensis - is a unique sub-species of the continental 'common vole' - a species which has never been found anywhere in the UK but in Orkney.
The Orkney vole was introduced in Neolithic times. Debate rages over as to whether it was deliberately introduced by Neolithic peoples, or got here as a stowaway in their boats, or whether it arrived naturally on floating rafts of vegetation from continental Europe (perhaps as sea levels rose, engulfing Doggerland, under what is now the North Sea). Bizarrely, although it is now absent on Hoy, Orkney vole bones have been found from archaeological digs there.
The Orkney vole provides an excellent food source for the short-eared owl and hen harrier. These birds of prey are much commoner on islands with voles.
Perhaps the best loved of our mammals is the otter. These are very shy and retiring mammals, normally just coming out under the hours of darkness. However, they occur in most lochs, burns and coastline. The best place to see them tends to be where freshwater comes into the sea. Spots like Brig o’Waith have more than their fair share of sightings.