and channel them into a relatively narrow corridor, large numbers can build up, leading to social friction, distress, and eventually a mass panic can follow, where they flee in all directions. Lemmings do migrate, and in vast numbers sometimes, but notion of a deliberate march into the sea is false. According to genetic research, the Norwegian lemming survived the Pleistocene glaciation in western Europe, inhabiting various refugia which were not covered by ice. Alternatively, some researchers have contended the Norwegian lemming populations had arisen from ancestors of the present-day brown lemming (Lemmus sibiricus), moving in after glaciers receded. The Novaya Zemlya lemming, which could represent either a subspecies of L. lemmus, or a population of L. sibiricus with mtDNA introgression from ancient hybridization with L. lemmus, supports the former theory. Despite their diminutive size, when confronted at close quarters by a potential predator, mainland Norway lemmings characteristically become highly aggressive. They have also been known to attack approaching humans. It has been suggested that they may be considered an aposematic subspecies, in that they appear to deter predation by using their prominent coloration, loud calls, and aggressive behavior to advertise their ability to harm small predators (in contrast to the less conspicuous voles). On the other hand, when viewed from a distance, their coloration may also facilitate a cryptic defence option by helping them to fade into the background. The "Novaya Zemlya lemming" In 2021, a taxonomic study analyzing a distinct population of lemmings on Novaya Zemlya, previously thought to be Siberian brown lemmings (Lemmus sibiricus), found them to be more closely related to L. lemmus, and reclassified them as a new subspecies L. lemmus chernovi, or the Novaya Zemlya lemming, named after zoologist and academician of the Russian Academy of Sciences, Yury I. Chernov. It is currently only known from the southern island of the archipelago. It is thought that prior to the Eemian Interglacial, L. lemmus was distributed widely throughout the Arctic Shelf from Western Europe east to Novaya Zemlya, and sea level rise during the Eemian left the species in its present day disjunct distribution, with populations only on Fennoscandia and Novaya Zemlya. Novaya Zemlya may have served as a refugium for cold-adapted terrestrial fauna such as L. lemmus during the Pleistocene interglacial periods. The Novaya Zemlya lemming lacks the aposematic coloration of the Norway lemming, being dull in color and lacking antipredator adaptations. It is thought