The mountain hare (Lepus timidus), also known as blue hare, tundra hare, variable hare, white hare, snow hare, alpine hare and Irish hare, is a hare that is largely adapted to polar and mountainous habitats. This species is distributed from Fennoscandia to eastern Siberia; in addition, isolated mountain populations occur in the Alps, Scotland, the Baltics, northeastern Poland, and Hokkaidō. In Ireland, the Irish hare (L. t. hibernicus) does not grow a white winter coat, is smaller in size, and lives on lowland pastures, coastal grasslands, and salt marshes, not just in the mountains. The mountain hare has also been introduced to Iceland, Shetland, Orkney, the Isle of Man, the Peak District, Svalbard, Kerguelen Islands, Crozet Islands, and the Faroe Islands. In the Alps, the mountain hare lives at elevations from 700 to 3800 m, depending on geographic region and season. The mountain hare is a large species, though it is slightly smaller than the European hare. It grows to a length of 45–65 cm (18–26 in), with a tail of 4–8 cm (1.6–3.1 in), and a mass of 2–5.3 kg (4.4–11.7 lb), females being slightly heavier than males. They can live for up to 12 years. In summer, for all populations of mountain hares, the coat is various shades of brown. In preparation for winter most populations molt into a white, or largely white, pelage. The tail remains completely white all year round, distinguishing the mountain hare from the European hare (Lepus europaeus), which has a black upper side to the tail. The subspecies Lepus timidus hibernicus, the Irish mountain hare, stays brown all year and individuals rarely develop a white coat. The Irish hare may also have a "golden" variation, particularly those found on Rathlin Island. In the Faroe Islands, mountain hares turn grey in the winter instead of white. The winter-grey color may be caused by downregulation of the agouti hair cycle isoform in the autumn molt. The diet of the mountain hare varies from region to region. It seems to be somewhat dependent on the particular habitat in which the population under study lives.