Lake Baikal mountain vole

The Lake Baikal mountain vole or Olkhon mountain vole (Alticola olchonensis) is a species of rodent in the family Cricetidae. It is found principally on the Olkhon and Ogoi islands on Lake Baikal, in southern Siberia. It is also found in a small part of the bordering mainland Russia, on the Baikal coast of the Irkutsk Oblast. It was originally described as a subspecies of the silver mountain vole. Since then, it has been synonymized with A. roylei in 1978, A. tuvinicus, and A. macrotis before reinstating it as a species. It is likely a sister species to A. tuvinicus.