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The water vole (''Microtus richardsoni'') is the largest North American vole. It is found in the northwestern United States and southern parts of western Canada. 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.〔 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.〔Klaus, M., Moore, R., & Vyse, E. (2001, July). Microgeographic variation in allozymes and mitochondrial DNA of Microtus richardsoni, the water vole, in the Beartooth Mountains of Montana and Wyoming, U.S.A. Canadian Journal of Zoology, 79(7), 1286-1295. Retrieved March 20, 2015, from http://www.nrcresearchpress.com.ezproxy.lib.utah.edu/doi/abs/10.1139/z01-082#.VQxqjHzF-Sp〕 These animals have gray-brown or red-brown fur with gray under parts. Their large hind feet help make them excellent swimmers, and they are found in alpine or semi-alpine meadows near water. They feed on grasses, leaves, roots and seeds, also eating small invertebrates. Water voles dig subterranean burrows that are connected to water sources, and are considered a semi-aquatic species.〔 They are active year-round, tunneling through snow during the winter. Their burrows often have entrances at the water's edge or under water,〔Ludwig, D. (1984, November 14). Microtus richardsoni. Mammalian Species, 223, 1-6. Retrieved March 20, 2015, from http://www.science.smith.edu/msi/〕 and they usually live in colonies of 8-40 individuals along the waterway.〔Ludwig, D. (1988). Reproduction and population dynamics of the water vole, Microtus richardsoni. Journal of Mammalogy, 69(3), 532-541. Retrieved March 20, 2015, from http://www.jstor.org/stable/1381345〕 == Etymology == Vole originated in approximately 1805, and is short for vole-mouse, which means field mouse. Vole originated from the Norwegian word vollmus; voll, meaning field, and mus, meaning mouse. It is also possible that there were influences from Swedish vall, which translates to mean field.〔Vole. (2014, March 25). Retrieved March 20, 2015, from http://www.wordsmith.org/words/vole.html〕 Microtus richardsoni is also known as: Richardson's Water Vole, Richardson Vole, Richardson's Meadow Vole, Richardson Meadow Mouse, Water Rat, Big-footed Mouse, Giant Water Vole, and Water Vole.〔North American Mammals: Microtus richardsoni. (n.d.). Retrieved March 20, 2015, from http://www.mnh.si.edu/mna/image_info.cfm?species_id=176〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Water vole (North America)」の詳細全文を読む スポンサード リンク
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