BIOLOGICAL DATA AND HABITAT REQUIREMENTS
WILDLIFE SPECIES: Microtus pennsylvanicus | Meadow Vole 



TIMING OF MAJOR LIFE HISTORY EVENTS : 
Meadow voles are active year-round [4,31].

Diurnal Activity:  Meadow voles are active day or night, with no clear
24-hour rhythm in many areas [66].  Most changes in activity are imposed
by season, habitat, cover, temperature, and other factors.  Meadow voles
have to eat frequently, and their active periods (every 2 to 3 hours)
are associated with food digestion [4,31].  In Canada meadow voles are
active the first 3 hours after dawn and during the 2- to 4-hour period
before sunset.  Most of the nonactive period is spent in the nest [31].

Gestation and Development of Young:  Gestation lasts 20 to 23 days [31].
Neonates are pink and hairless, with closed eyes and ears.  Fur begins
to appear by 4 days, and young are completely furred except for the
belly by 7 days.  Eyes and ears open by 8 days.  Weaning occurs from 12
to 14 days.  Young born in spring and early summer attain adult weight
in 12 weeks, but undergo a fall weight loss.  Young born in late summer
continue growing through the fall and maintain their weight through the
winter.  Maximum size is reached between 2 and 10 months [31,48].

Litter Size and Productivity:  Typical meadow vole litters consist of 4
to 6 young, with extremes of 1 and 11 young.  On average 2.6 young are
successfully weaned per litter.  Litter size is not significantly
correlated with latitude, elevation, or population density.  Fall,
winter, and spring litters tend to be smaller than summer litters.
Reich [48] found that litter size was positively correlated with body
size, and is not significantly different in primaparous and multiparous
females.  Another report stated that primaparous females had fewer young
per litter than multiparous females [31].  Litter size was constant in
summer breeding periods at different population densities [48].  Female
meadow voles reach reproductive maturity earlier than males; some
ovulate and become pregnant as early as 3 weeks.  Males are usually 6 to
8 weeks old before mature sperm are produced [31].  One captive female
meadow vole produced 17 litters in 1 year for a total of 83 young.  One
of her young produced 13 litters (totalling 78 young) before she was 1
year old [3].  If breeding began in April, it was estimated that 100
pairs of montane voles (Microtus montanus) in 40 acres could create a
density of 8,900 voles by September [43].

Mortality and Longevity:  Patterns of mortality apparently vary among
meadow vole populations.  According to Banfield [4] the average meadow
vole lifespan is less than 1 month because of high nestling and juvenile
mortality.  The average time that adults are recapturable in a given
habitat is about 2 months, suggesting that the average extended lifespan
(i.e. how much time adult meadow voles have left) is about 2 months, not
figuring in emigration [4].  Getz [23] reported mortality of 88 percent
for the first 30 days after birth.  Golley [25] reported that
postnestling juveniles had the highest mortality rate (61%), followed by
young adults (58%) and older age groups (53%).  He estimated that
nestlings had the lowest mortality rate (50%).  Estimated mean longevity
ranges from 2 to 3 months to 10 to 16 months [48].  Banfield [4]
reported that the maximum lifespan in the wild is 16 months, and Johnson
and Johnson [31] stated that few voles live more than 2 years.

Population Density and Population Cycles:  Meadow vole populations
fluctuate annually and also tend to reach peak densities at 2- to 5-year
intervals, with population declines in intervening years [4,31,35].
Breeding often ceases in January and starts again in March [31].  Over
the course of a year, meadow vole populations tend to be lowest in early
spring; the population increases rapidly through summer and fall [31].

In years of average population sizes, typical meadow vole population
density is about 15 to 45 meadow voles per acre in old-field habitat.
In peak years meadow vole population densities may reach 150 meadow
voles per acre in marsh habitat (more favorable for meadow voles than
old fields) [4].  Fritzell [20] stated that peak meadow vole abundance
can exceed 1,482 meadow voles per acre (600/ha) in northern prairie
wetlands.  Meadow voles in optimal habitats in Virginia (old fields with
dense vegetation) reached densities of 983 per acre (398/ha);
populations declined to 67 per acre (27/ha) at the lowest point in the
cycle [38].  Different factors influencing population density have been
assigned primary importance by different authors.  Reich [48] listed the
following factors as having been suggested by different authors:  food
quality, predation, climatic events, density-related physiological
stress, and the presence of genetically determined behavioral variants
among dispersing individuals.

Normal population cycles do not occur when dispersal is prevented; under
normal conditions dispersers have been shown to be behaviorally,
genetically, and demographically different from residents [48].  Birney
and others [7] hypothesized that there is a threshold density of cover
needed for meadow vole populations to increase.  Above the threshold
amount the quantity of cover influences the amplitude and possibly the
duration of the population peak.  Local patches of dense cover could
serve as source populations or reservoirs to colonize less favorable
habitats with sparse cover [7].

Social Interaction:  Meadow voles form extensive colonies and develop
communal latrine areas.  They are socially aggressive and agonistic;
females dominate males and males fight amongst themselves [4].


PREFERRED HABITAT : 
Optimal meadow vole habitat consists of moist, dense grassland with
substantial amounts of plant litter.  Habitat selection is largely
influenced by relative ground cover of grasses and forbs; soil
temperature, moisture, sodium, potassium, and pH levels; humidity; and
interspecific competition [17,50].  Meadow voles are most commonly
associated with sites having high soil moisture [46].  They are often
restricted to the wetter microsites when they occur in sympatry with
prairie voles (Microtus ochrogaster) or montane voles [17].  In an Iowa
prairie restoration project, meadow voles experienced an initial
population increase during the initial stage of vegetation succession
(old field dominated by foxtail grass [Setaria spp.], red clover
[Trifolium pratense], annual ragweed [Ambrosia artemisiifolia], alfalfa
[Medicago sativa], and thistles [Cirsium spp.]).  However, meadow vole
populations reached their peak abundance during the perennial grass
stage of succession from old field to tallgrass prairie [53].  Geier and
Best [22] found meadow voles in habitat devoid of tree cover in which
grasses dominated the herb layer.  They listed the meadow vole as a
species with low tolerance for habitat variation (i. e., a species that
is intolerant of variations in habitat, is restricted to few habitats,
and/or uses habitats less evenly than tolerant species) [22].
 
In most areas meadow voles clearly prefer habitat with dense vegetation.
In tallgrass prairie at Pipestone National Monument, meadow voles were
positively associated with dense vegetation and litter [57].  Conley and
others [11] reported that variables important to meadow vole habitat in
Virginia include vegetative cover reaching a height of 8 to 16 inches
(20-41 cm) and presence of litter.  Meadow voles appeared to be randomly
distributed within a grassland habitat in southern Quebec [26].  Grant
and Morris [26] were not able to establish any association of meadow
vole abundance with particular plant species.  They were also unable to
distinguish between food and cover as the determining factor in meadow
vole association with dense vegetation.

In eastern Massachusetts meadow vole density on a mosaic of grassy
fields and mixed woods was positively correlated with decreasing
vertical woody stem density and decreasing shrub cover.  Meadow vole
density was highest on plots with more forbs and grasses and less woody
cover; meadow voles preferred woody cover over sparse vegetation where
grassy cover was not available [1].

In West Virginia the only forested habitats in which meadow voles were
captured were seedling stands [9].  In South Dakota meadow voles prefer
grasslands to Rocky Mountain juniper (Juniperus scopulorum) woodlands
[55].  In New Mexico meadow voles were captured in stands of grasses,
wild rose (Rosa spp.), prickly-pear (Opuntia spp.), and various forbs;
meadow voles were also captured in wet areas with tall marsh grasses
[18].

Open habitat with a thick mat of perennial grass favors voles [39].  In
west-central Illinois meadow voles were the most common small mammals on
Indian grass (Sorghastrum nutans)-dominated and switchgrass (Panicum
virginicus)-dominated study plots.  They were present in very low
numbers on orchard grass (Dactylis glomerata)-dominated plots.  The most
stable population of meadow voles occurred on unburned big bluestem
(Andropogon gerardii)-dominated plots [42].  In Ontario meadow voles and
white-footed mice (Peromyscus leucopus) occur together in ecotones.
Meadow voles were the most common small mammals in oak savanna/tallgrass
prairie dominated by northern pin oak (Quercus palustris) and grasses
including bluejoint reedgrass (Calamagrostis canadensis), prairie
cordgrass (Spartina pectinata), big bluestem, switchgrass, and Indian
grass.

Effect of Habitat Alteration:  In Michigan strip clearcuts in a conifer
swamp resulted in an increase in the relative abundance of meadow voles.
Meadow voles were most abundant in clearcut strip interiors and least
abundant in uncut strip interiors.  Slash burning did not appear to
affect meadow vole numbers about 1.5 years after treatment [64].

Dispersal Distance:  In Pennsylvania three subadult meadow voles were
captured at least 1.6 miles (2.6 km) from the nearest appreciable
suitable meadow vole habitat, suggesting that meadow voles are adapted
to long-distance dispersal [34].

Habitat Patch Shape:  In Ohio the effects of patch shape and proportion
of edge were investigated by mowing strips between study plots.  The
square plots were 132 feet per side (40 m x 40 m), and the rectangular
patches were 52.8 feet by 330 feet (16 m x 100 m).  Square habitat
patches were not significantly different than rectangular patches in
meadow vole density.  There were no apparent edge effects in patches of
this size, suggesting that meadow voles are edge-tolerant.  Habitat
patch shape did affect dispersal and space use behaviors.  In
rectangular patches home ranges were similar in size to those in square
patches, but were elongated [29].

Home Range:  Meadow voles tend to remain in home ranges and defend at
least a portion of the home range from conspecifics.  Home ranges
overlap and have irregular shapes [31].  Meadow vole home range size
depends on season, habitat, and population density:  ranges are larger
in summer than winter, ranges in marshes are larger than ranges in
meadows, and ranges are smaller at higher population densities [48].
Home ranges vary in size from 0.08 to 2.3 acres (0.32-0.9 ha).  Females
have smaller home ranges than males, but are more highly territorial
than males; there is often a period when juveniles from one litter are
still present in the adult female's home range when the next litter is
borne [4,31].  Female territoriality tends to determine density in
suboptimal habitats; the amount of available forage has been suggested
as the determining factor in female territory size and therefore also
determines reproductive success [32].


COVER REQUIREMENTS : 
Nests are used as nurseries, resting areas, and as protection against
weather.  They are constructed of woven grass.  Nests are usually
subterranean or are constructed under boards, rocks, logs, brush piles,
hay bales, fenceposts, or in grassy tussocks.  Meadow voles dig shallow
burrows [31], and in burrows, nests are constructed in enlarged
chambers.  In winter nests are often constructed on the ground surface
under a covering of snow, usually against some natural formation such as
a rock or log [4,31].

Meadow voles form runways or paths in dense grasses [4,31].


FOOD HABITS : 
Meadow voles eat most available species of grasses, sedges, and forbs
including many agricultural plant species [31,48].  In summer and fall
grasses are cut into match-length sections to reach the succulent
portions of the leaves and to reach seedheads.  Leaves, flowers, and
fruits of forbs are also typical components of the summer diet.  Fungi,
primarily endogones (Endogone spp.), have been reported in meadow vole
diets.  Meadow voles occasionally consume insects and snails.  Meadow
voles occasionally scavenge on animal remains, and cannibalism is
frequent in periods of high population density.  Meadow voles may damage
woody vegetation by girdling when population density is high [48].

In winter meadow voles consume green basal portions of grass plants,
often hidden under snow.  Other winter diet components include seeds,
roots, and bulbs.  Meadow voles occasionally strip the bark from woody
plants.  Seeds and tubers are stored in nests and burrows [4,31].
Evidence of coprophagy is sparse but it is thought to occur [31].

In an old-field community in Quebec, plants preferred by meadow voles
included quackgrass (Elytrigia repens), sedges, fescues (Festuca spp.),
wild strawberry (Fragaria virginiana), timothy (Phleum pratense),
bluegrasses (Poa spp.), and bird vetch (Vicia cracca) [5].


PREDATORS : 
Meadow voles are an important prey for many hawks, owls, and mammalian
carnivores, and they are also taken by some snakes [48].  Almost all
species of raptors take microtine (Microtus spp.) rodents as prey.
Birds not usually considered predators of mice do take voles; examples
include gulls (Larus spp.), northern shrike (Larius borealis),
black-billed magpie (Pica pica), common raven (Corvus corvax), American
crow (C. brachyrhynchos), great blue heron (Ardea herodias), and
American bittern (Botaurus lentiginosus) [31].  In Ohio meadow voles
comprised 90 percent of the individual prey remains in long-eared owl
(Asio otus) pellets on a relict wet prairie [44], and in Wisconsin
meadow voles comprised 95 percent of short-eared owl (A. flammeus) prey
[14].  Most mammalian predators take microtine prey [31].  The
short-tailed shrew (Blarina brevicauda) is major predator; meadow voles
avoid areas frequented by short-tailed shrews [48].  Other major
mammalian predators include badger (Taxidea taxus), striped skunk
(Mephitis mephitis), weasels (Mustela spp.), marten (Martes americana),
and domestic cat (Felis cattus).  Other animals reported to have
ingested voles include trout (Salmo spp.), Pacific giant salamander
(Dicampton ensatus), garter snake (Thamnophis spp.), yellow-bellied
racer (Coluber constrictor), gopher snake (Pituophis melanoleucas),
rattlesnake (Crotalus viridis), and rubber boa (Charina bottae) [31].

In northern prairie wetlands meadow voles are a large portion of the
diets of red fox (Vulpes vulpes), mink (Mustela vison), short-eared owl,
and northern harrier (Circus cyaneus) [20].  Voles (Microtus spp.) are
frequently taken by racers (Coluber spp.); racers and voles often use
the same burrows [41].


MANAGEMENT CONSIDERATIONS : 
Meadow voles are abundant in agricultural habitats.  The list of crops
that are damaged by meadow voles is long and includes root and stem
crops (asparagus, kohlrabi), tubers, leaf and leafstalks, immature
inflorescent vegetables (artichoke, broccoli), low-growing fruits
(beans, squash), the bark of fruit trees, pasture, grassland, hay, and
grains [31].  Meadow voles are listed as pests on forest plantations
[2].  In forest plantations in British Columbia an apparently abundant
(not censused) meadow vole population was associated with a high rate of
"not sufficient regeneration"; damage to tree seedlings was attributed
to meadow voles and lemmings (Synaptomys spp.) [60].  In central New
York colonization of old fields by trees and shrubs was reduced due to
seedling predation by meadow voles, particularly under the herb canopy
[24].

Management of meadow vole abundance in agricultural areas includes
reduction of habitat in waste places such as roadsides and fencerows by
mowing, plowing, and herbicide application.  Predators, particularly
raptors, should be protected to keep meadow vole populations in check.
Direct control methods include trapping, fencing, and poisoning;
trapping and fencing are of limited effectiveness.  Poisons are
efficient. Repellents are largely ineffective at present [31].  Pauls
[45] reported that plastic mesh cylinders were effective in preventing
seedling damage by meadow voles and other rodents.  Properly timed
cultivation and controlled fires are at least partially effective in
reducing meadow vole abundance.

The cycle of meadow vole abundance is an important proximate factor
affecting the life histories of its major predators.  Meadow voles are
usually the most abundant small mammals in northern prairie wetlands,
often exceeding 40 percent of all individual small mammals present [20].
Numbers of short-eared owls, northern harriers, rough-legged hawks
(Buteo lagopus), coyotes (Canis latrans), and red foxes were related to
large numbers of meadow voles in a field in Wisconsin [14].  Other
authors have also stated that predator numbers are positively associated
with meadow vole abundance [31,65].

Ecto- and endoparasites have been reported for meadow voles by a number
of authors and include trematodes, cestodes, nematodes,
acanthocephalans, anoplura, siphonaptera, diptera, and acarina [31,48].

Human diesases transmitted by microtine rodents include cystic hydatid
disease, tularemia, bubonic plague, babesiasis, and giardiasis [31].


REFERENCES : 
NO-ENTRY

Related categories for Wildlife Species: Microtus pennsylvanicus | Meadow Vole