151.

Creeping Vole

Microtus oregoni

French: Campagnol de I'Oregon / German: Oregon-Wihimaus / Spanish: Topillo de Oregén

Other common names: Oregon Meadow Mouse, Oregon Vole

Taxonomy. Arvicola oregoni Bachman, 1839, Astoria, Clatsop County, Oregon, USA. Four subspecies are recognized.

Subspecies and Distribution.

M.o.oregon:Bachman,1839—WWashington,WOregon,andNWCalifornia,USA.

M.o.adocetusMerriam,1908—extremeSCOregonandNCCalifornia,USA.

M.o.bairdiMerriam,1897—SCOregonandextremeNCCalifornia,USA.

M. o. serpens Merriam, 1897 — SW British Columbia, Canada.

Descriptive notes. Head-body 97-112 mm, tail 32-42 mm, ear 9-10 mm, hindfoot 19-19 mm; weight averages 19 g. The Creeping Vole is one of the smallest species of Microtusin North America and has a very shorttail. Pelage is dense, soft, and sooty gray to yellowish brown on back; venter is dusky. Tail is indistinctly bicolored, and ears are small, blackish and lightly haired. Hindfeet have five plantar tubercles. Molars are small, M? has 2-3 closed triangles, M, has five closed triangles, and M, has three transverse loops.

Habitat. Dry short-grass habitats in coniferous forests. Clearcut disturbed sites and areas where timber slash has been burned support higher densities of Creeping Voles because of the herbaceous-dominated vegetation.

Food and Feeding. Diets of Creeping Voles primarily include herbaceous vegetation (forbs and grass) and fungi. Captive individuals have survived on bluegrass, clover, and apples.

Breeding. Breeding of Creeping Volesis reportedly year-round but mostly in March— September. Gestation is ¢.23 days, and 4-5 litters with 3-4 young each are produced annually. Young are born in nests of dry grass placed in cavities under logs or in similarly protected sites.

Activity patterns. Creeping Voles are terrestrial.

Movements, Home range and Social organization. It is unknown if Creeping Voles undergo large multiannual population fluctuations, as often recorded for other species of Microtus . They are known to tunnel but not exclusively, and they often use aboveground runways. Home ranges are 0-05-0-38 ha for males and 0-04—0-23 ha for females; they decrease in size through summer. Densities have been reported as high as 138 ind/ha at the northern edge of the distribution in British Columbia, but much lower in the south.

Status and Conservation. Classified as Least Concern on The IUCN Red List.

Bibliography. Bradley, Ammerman et al. (2014), Carraway & Verts (1985), Cowan & Arsenault (1954), Hall (1981), Hooven (1973), Musser & Carleton (2005), Verts & Carraway (1988).