OCTOBER 1989 - City of Boulder

MEAD(KJ VOLE I
Micotus penns~lvanicus
Distribution--The meadow vole has the most extensive range of
any North American microtine, except the muskrat, occuring throughout
Canada, the northern and eastern United States, and southward into
Mexico. In Colorado, the species occurs in the valley of the South Platte
River and in the mountains on the Eastern Slope, eastward on the Platte-
Arkansas Divide at least to Ramah. On the Mountain arks, it has
been captured at the foot of the First Flatiron and in Skunk Canyon.
Description--The meadow vole is a medium-sized, robust-bodied
mouse with small eyes and ears and short legs. It is distinguishable
from other voles by its larger size and relatively short tail. Its
fur is long and soft, the summer pelage being sparser and coarser than
winter, and the color varies from gray faintly washed with brown to dark
brown, the belly being silvery to slightly buffy or dark gray. The tail
is bicolored.
Measurements of three males and two females from Larimer County
were: total length, 192, 180, 185, 187, 178; tail, 54, 44, 67, 56, 50;
hindfoot, 23, 21, 22, 23, 22; ear, 15, --, 13, 15, 14; weight, 73.61,
--, 68.49 gr. Condylobasal length ranges from 29.4 to 30.2, zygomatic
breadth from 16.3 to 17.7.
Natural History--Meadow voles seem to prefer moist grasslands or
wetlands, but are occasionally found in orchards or wooded areas with
little ground cover. Choice of habitat seems to be related to the
presence of sympatric species. The meadow vole is reported to be
subordinate to other Microtus species. Voles are inclhed to make.
surface runways in dense grass or sedge cover, and may burrow if the
soil-is not too waterlogged. They are good swimmers. Spherical nests
are constructed of leaves and coarse grasses with softer vegetation
as lining, and are usually found on the ground surface. The animals
may be active both day or night, depending on temperature and ground
cover; they do not hibernate. Meadow voles tend to be solitary, and
breeding is promiscuous.
Voles are said to eat their own weight in food each day. Diet
consists primarily of grasses, &, Panicum, and Muhlenbergia being
prominent, but the voles will also eat grain, seeds, bark, roots, fruits,
flowers, fungi, and sometimes insects. The animals may store food
against thin seasons.
Mating in meadow voles occurs throughout the year, with up to 17
litters of one to nine young being born per year. Young are altricial,
are weaned about two weeks, and are independent soon after. Females
begin reproducing in about a month, and males about two weeks later.
This vole is said to have more species of predators than any other
North American mammal. Owls, hawks, snakes, weasels, foxes, and most
other carnivores will prey on them. Densities of vole populations tend
to tun in cycles of two to five years. At high densities, this may
cause serious damage, especially in orchards, due to girdling.
--
Selected References-Brown (1977), Jones et al.(in press);
Reich (1981).
S.T.G. .