A New Subspecies of Microtus montanus from Montana and Comments on Microtus canicaudus Miller

In the early 1950s, field biologists revisited a pair of meadow vole specimens collected in Montana’s Bitterroot Valley, only to discover that they did not match any known subspecies. By comparing these samples with additional material from the United States National Museum, the researchers identified a distinct population inhabiting the Flathead and Bitterroot valleys, prompting the formal description of a new subspecies of Microtus montanus.

The new form is modestly smaller than its close relatives, with a notably inflated tympanic bullae, a subtly different skull shape, and a shorter tail and hind foot. Detailed measurements set it apart from the nearby M. m. nanus, highlighting subtle geographic variation within the species. This work not only refines the taxonomy of North American voles but also underscores how careful examination of museum collections can reveal hidden biodiversity in familiar landscapes.