Microtus pennsylvanicus
(Meadow Vole)

Description:
The genus name “microtus” literally mean “small ear”, so this vole and others in the genus Microtus have small ears. Meadow voles are quite dark, dark gray to almost blackish above, but this color is variable. Their feet are dark, and they have a slightly bicolored tail. The tail is about twice the length of the hind foot. They are difficult to distinguish from montane voles. Total length is 6.7 to 7.4 inches (160-185 mm), tail length is 1.8 to 2.4 inches (45-60 mm), and they weigh 1 to 2.3 ounces (30-65 g).

Range:
Most of Canada and Alaska, south through northern half of U.S. to Oregon, northern Utah, central New Mexico, northern Missouri, and Georgia. Has greatest distribution of any vole species in North America.

Habitat:
Found in variety of habitats, from dry pastures and weeded swamps to marshes and orchards. Needs loose organic soils for tunneling. In Idaho, prefers moist grasslands, woodlands, and meadows.

Diet:
Eats vegetable matter such as grasses, roots, and seeds.

Ecology:
The meadow vole and other voles exhibit a distinct population cycle of 2 to 4 years. During this cycle, population at the low point can be 1 to several per acre (0.4 ha) to nearly 100 per acre (0.4 ha) at the peak of the cycle. Since this is such a short term cycle ( 2 to 4 years), predators that rely on meadow voles as prey during the peak of the cycle, need to switch prey during the low of the cycle. Meadow voles are active during the day (diurnal), so they tend to be preyed on by diurnal predators such as coyotes, hawks, weasels and others. They do not hibernate, but are active all winter. They nest on the ground in clumps of dry grass that are usually concealed under brush or logs. They use shallow burrows during the winter. They create distinctive runways in the dense vegetation of their habitat. The voles clip the grass to form the runways and they leave piles of clipped grass along the runways. Males have larger home ranges of about 0.5 acres (0.2 ha) than females (0.25 acre; 0.1 ha) This species has been extensively studied by population biologists, but the cause of their drastic, cyclic, population fluctuations has not yet been clearly elucidated.

Reproduction:
Meadow voles can breed year around, although winter breeding may only be associated with the availability of snow cover or the peak of the population cycle. Peak breeding activity occurs curing April to October. Gestation lasts approximately 21 days, and litter size varies from 1 to 9 young (average is 4 to 5). litter size is smaller in fall than in spring or summer. Young develop rapidly and are weaned at 12 to 14 days. They are capable of breeding at 4 to 6 weeks of age. Females may produce more than 5 litters per year. Their huge reproductive potential is dampened by a very high mortality rate. About 90 % of the young die in their first month of life. It has been calculated that only about 1 in 50 reaches 100 days old, which only allows it enough time to produce 3 litters in their life.

Conservation:

Status:	Unprotected nongame species
Global Rank:	G5
State Rank:	S5

Important State References:
Hoffman, G.R. 1960. The small mammal components of six climax plant associations in eastern Washington and northern Idaho. Ecology 41:571-572.