The Wrangel Island Lemming or Lemmus portenkoi, is a common species of lemming endemic to Wrangel Island in Russia. It was included as a subspecies of L. sibiricus by Jarrell and Fredga in 1993, while Chernyavskii (also in 1993) regarded it as a separate species. Lemmings are small rodents, usually found in or near the Arctic, in tundra biomes. They are subniveal animals and together with the voles and muskrats, they make up the subfamily Arvicolinae (also known as Microtinae), which forms part of the largest mammal radiation by far, the superfamily Muroidea, which also includes the rats, mice, hamsters, and gerbils.