Comments: The brown lemming was formerly referred to as Lemmus sibiricus, but the correct name for the North American population is Lemmus trimucronatus (Jarrell and Fredga 1993, Jones et al. 1997; also see following information). Batzli (in Wilson and Ruff 1999) used the name Lemmus sibiricus but acknowledged that Lemmus trimucronatus may be the correct name. The North American mammal checklist by Baker et al. (2003) listed this species as Lemmus trimucronatus, following Jarrel and Fedga (1993). Musser and Carleton (in Wilson and Reeder 2005) also recognized L. trimucronatus and L. sibiricus as distinct species, with only the former occurring in North America.
Pokrcvski et al. (1984) concluded that the brown lemmings in Siberia comprise two species, Lemmus sibiricus in the west and L. chrysogaster in the east. If the eastern Siberian form is conspecific with the North American form (see Rausch and Rausch 1975), then the correct name for the North American-eastern Siberian brown lemming is Lemmus trimucronatus (due to priority). If the North American form is not conspecific with L. chrysogaster, the correct name for the North American form is still Lemmus trimucronatus. North American brown lemmings can be called Lemmus sibiricus only if they are regarded as conspecific with the western Siberian population. See Musser and Carleton (in Wilson and Reeder 1993, 2005) for further taxonomic discussion.
Studies by Rausch and Rausch (1975) indicated that the population on St. George Island (L. t. nigripes) is best regarded as a subspecies, but some recent authors (but not Jones et al. 1992 or Musser and Carleton [in Wilson and Reeder 1993, 2005]) have continued to recognize nigripes as a distinct species.