(Micotus pennsylvanicus Ord)
From: Saunders, D. A. 1988. Adirondack Mammals. State University of New York, College of Environmental Science and Forestry. 216pp.
Description: Voles are small mammals that tend to have large heads, compact bodies, and short noses. Microtus means “small ear” and the voles of this genus have short ears that barely protrude from the fur surrounding them. The meadow vole is a typical representative of this group and has dull fur that is grizzled chestnut to yellowish brown on the upper parts of the body, silvery gray on the lower parts. The tail, about one-third of the total body length, is sparsely haired and scaly. Adults are 162-181 mm (6.4-7.1 in) in total length, and weigh approximately 46 g (1.6 oz).Range and Habitat: The meadow vole occurs throughout Alaska, Canada, the northern and eastern U.S., and into parts of Mexico. It prefers, as it name suggests, meadows containing grasses, sedges, and shrubs such as alders. Grassy openings within forests, abandoned fields, bogs, alpine tundra, and swamp edges also harbor populations. This species may occupy deciduous and mixed, coniferous-deciduous forests, but the use of these marginal habitats depends to some extent on population levels and the relative abundance of other small mammals. Even Merriam mentions the meadow vole’s scarcity in coniferous forests (p 272). This rodent resides in suitable areas at all elevations in the Adirondacks. Meadow voles may exclude other rodents such as deer and white- footed mice, bog lemmings, and red-backed voles from areas where they would otherwise be found, and in turn, meadow voles are seldom numerous in the places where short- tailed shrews are common.
Meadow voles construct surface runways and underground tunnels that may honeycomb an area. They build roughly globe-shaped nests from dried plants 15-20 cm (6-8 in) in diameter. These nests have on or more openings leading to tunnels and runways. The nests may be on the surface of the ground, in the open, against or within a log or stump, in a clump of grass, or underground.
Food and Feeding Behavior: Like many small herbivores, the meadow vole occasionally eats insects or other invertebrates but, grasses, sedges, seeds, tubers, and roots comprise most of the diet. Under the cover of snow, the meadow vole may girdle trees and shrubs, consuming the inner bark. Where meadow voles inhabit orchards or yards, the damage to woody vegetation may be extensive. Seeds and tubers stored underground in autumn are alternative winter foods. By cutting the stems of small plants for food or to reach seed heads, the meadow vole creates its maze of 2.5- 5.0 cm (1-2 in) wide runways.
Activity and Movement: As might be expected of a sometime resident of marshy areas, the meadow vole swims well, even diving briefly when pursued. The normal gait is running, punctuated with frequent sudden stops and starts. Activity peaks at dawn and dusk, but is modified by conditions such as bright moonlight, temperature, and the amount of vegetation cover; and continues during the winter under snow. Periods of rest alternate with other behavior.
Reproduction: The meadow vole is well known for its fecundity. One female, kept in a laboratory, gave birth to 17 litters in one year. With a life span averaging less than a year in the wild, most females produce only 1-2 litters. Females may bear litters during any month of the year that food is readily available, but more litters are born in spring and autumn, the fewest in winter. Winter breeding is most likely at high population densities. The gestation period is 21 days. Females give birth to 1-11 (average 4-6) young. The newborn voles are pink, hairless, and weigh about 2.3 g (0.1 oz) each. Their eyes open by 8 days, and they are weaned at 12-14 days. By their third week, they are independent. Young females mature sexually by 28 days, and they may begin breeding immediately. Males may commence breeding when 35 days of age. Potential longevity is 2.7 years.
Predators: The usual predators of small mammals eat meadow voles. Some of these are weasels, foxes, hawks, owls, the coyote, bobcat, and short-tailed shrew.
- Social system - During the breeding season, reproductively active females maintain territories from which they exclude other females. Males occupy home ranges of 0.08-0.3 ha (0.2 0.75 acre), about 3 times the size of a female’s territory. Males do not defend territories, but avoid others or fight during encounters. Their home ranges overlap, and include the territories of several females. Meadow voles are promiscuous. Males seek out estrous females, entering their territories, and if not rejected, mate quickly before being driven away. Several males may compete for the same estrous female. Competition among males may lead to intense hostile encounters, wounding, and possibly the establishment of temporary hierarchies. During the non-breeding season, both sexes have overlapping home ranges, and perhaps to conserve body heat, up to 7 may nest communally during the winter. Meadow vole populations peak at 2-5 year intervals. Climate, behavior, density, predators, and food quality are factors determining population levels. Population studies in various parts of the range indicate typical densities of 100-200 per ha (40-80 acre); in one study, 625 per ha (250 per acre).
- Communication - Chemical signs play a dominant role in the lives of these small rodents. Accumulations of droppings and urine traces in runways are likely clues about the identity, proximity, and sexual status of neighbors. Posturing and vocalizations during encounters are other signals. Newborn young emit 4 types of ultrasonic signals. Adults squeal, growl, and tooth chatter when threatened.
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