Wood lemming (Myopus schisticolor) — a newcomer in Estonian mammal fauna?

The wood lemming (Myopus schisticolor, Lilljeborg 1844) is the only extant species of Myopus, and its closest relatives are found in the genus of the true lemmings (Lemmus). The range of the wood lemming, which is considered a monotypic species, stretches from the Fennoscandian Peninsula through Northern and Central Russia to the Pacific Coast of the Russian Far East. Historically, there have been no records of wood lemmings in the Baltic States. Unexpectedly, during 2019–2020, nine wood-lemmings were recorded with a surprisingly wide spread in Estonia. A DNA analysis carried out on six wood lemmings revealed two mtDNA haplotypes. One of the haplotypes was previously known haplotype H5, described as a basal haplotype for the Western lemming group. The second one was a novel haplotype, probably derived from haplotype H5. The origin of the species remains unclear. We propose three competing hypotheses: the wood-lemming was an unnoticed part of the local fauna, it arrived in Estonia during the peak abundance period and has spread throughout the country since then, or it was unintentionally brought to the country by human activities such as log import.