This animal has been historically considered a member of genus Arvicola, but molecular evidence demonstrates that it is more closely related to North American Microtus species.

[2][3] Water voles are on the USDA Forest Service Region 2 sensitive species list because they maintain very small populations and there is high concern that their required habitat may be declining.

[9] Although this animal has been historically considered a member of genus Arvicola, molecular evidence demonstrates that it is more closely related to North American Microtus species.

Paleontological evidence suggests that M. richardsoni diverged from a Mimomys ancestral form in Siberia approximately 1.5 million years before Arvicola evolved in Europe.

Water voles live in two distinct bands through the western United States and Canada, extending from British Columbia and Alberta through parts of Oregon, Washington, Montana, Idaho, Wyoming, and Utah.

The distribution of habitats is found to be extremely variable, due to the geographical barriers of large coniferous forests, mountains, and expansive valleys without readily available waterways.

[4] Because water voles live in such small isolated patches it is necessary for them to form such a metapopulation structure, in which dispersal can balance out local extinction.

[10] Their main source of food is vegetation, including leaves, stems, grasses, sedges, willows, and sometimes seeds or insects.

[4] Water voles are most active at night, and they travel between tunnels, nests and waterways by means of surface runways 5–7 cm wide through the vegetation.

They construct these tunnels and nests just below the roots of the vegetation (about 4–6 cm below ground) during the breeding season (June through late September).

[5] Both males and females have rather large flank glands, which serve to mark territories so that nests are not invaded by others, as well as signaling to mates during the breeding season.

[10] Although water voles appear to have the ability to reproduce in large numbers, as do many other rodents, their population densities are actually kept very low and live in colonies of 8-40 individuals.

[5] Approximately 26% of young males and females begin to reproduce during the breeding season of their birth,[6] but overwintered adults are responsible for most of the reproduction.

[11] The presence of livestock presents numerous detrimental changes to the water vole's habitat: altered abiotic characteristics, compacted soil, increased runoff, fractured stream banks, erosion, as well as loss of vegetation as protective cover and a food source.