field mouse

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Meadow Vole
Conservation status
Least Concern (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Rodentia
Family:	Cricetidae
Genus:	Microtus
Subgenus:	Mynomes
Species:	M. pennsylvanicus
Binomial name
Microtus pennsylvanicus (Ord, 1815)

The Meadow Vole (Microtus pennsylvanicus), sometimes called the Field Mouse or Meadow Mouse, is a small North American vole found across Canada, Alaska and the northern United States. Its range extends further south along the Atlantic coast. One subspecies, the Florida Salt Marsh Vole (M. p. dukecampbelli), is found in Florida, and is classified as endangered. It is also found in Chihuahua, Mexico.

The Meadow Vole is active year-round, usually at night. It also digs underground burrows where it stores food for the winter and females give birth to their young. Although these animals tend to live close together, they are aggressive towards one other. This is particularly evident in males during the breeding season. It can cause damage to fruit trees, garden plants and commercial grain crops.

Taxonomy

The Meadow Vole is a small mammal and is one of twenty six other rodent species native to North America which is called a vole.^[1] The meadow vole's scientific name is Microtus pennsylvanicus or M. pennsylvanicus. It is classified in Kingdom Animalia, phylum chordata, class mammalia, order rodentia, and family muridae.^[2] M. pennsylvanicus is sometimes alternatively called the Field Mouse or Meadow Mouse.^[3]

Physical characteristics

The Meadow Vole has a long, cylindrical, fur-covered body with chunky build and a short tail. It has a rounded nose and ears that are partially buried in its black or brown fur. Their fore and hind paws differ in that the front paws have four toes whereas their hind paws have five.^[4] On average, they are 16 cm in length and weigh about 50 grams.^[5]

Habitat and niche

A Meadow Vole

M. pennsylvanicus is the most widespread of any other rodent group, ranging from Mexico to the Arctic.^[6] They can be found throughout Northern and Eastern United States and right across Canada, from Newfoundland and Labrador to British Columbia, including the Yukon Territory and Alaska. Because of the broad range of climates found within these areas, M. pennsylvanicus has varying phenotypic characteristics depending on the environment, having a larger body size in cold climates and a smaller body size in warmer climates.^[7] They often live in open fields as opposed to heavily wooded areas, and are abundant in areas with a high degree of plant cover. If an area experiences an event which results in a decrease in its amount of plant cover, such as the activity of grazing animals, it will result in a decrease in the abundance of meadow voles in that area. The meadow voles prefer the areas of increased plant cover because it allows them to hide from predators.^[8][9] The meadow vole is so strongly attracted to areas of dense plant cover that even the presence of the scent of a predator will not discourage the meadow voles from remaining in that area.^[10] During the winter, M. pennsylvanicus tends to remain below the surface in snowy tunnels. They make their winter nests under the snow yet still above the surface of the ground. In the spring, they will move from their above-ground snow tunnels to an underground network of burrows and will build a globular summer nest from dry grass.^[11]

Diet

The Meadow Vole is a herbivore, feeding mainly on the grasses that are abundant in its environment. When grass is not readily available, such as during the winter months, the meadow vole may often gnaw on tree bark as a source of nourishment.^[12] They often will eat nuts and seeds when available. In captivity, they will frequently feed on lettuce and sunflower seeds as supplements to their diets.^[13] The parts of the plant which the meadow vole will most likely feed on depends on the nutritional value of the part of the plant. They prefer parts of plants with high amounts of digestible energy and nutrients, while they tend to avoid the parts containing large quantities of fiber. This is because fiber is difficult to digest and will therefore be an inefficient source of calories. Though if poorly digestible food is all that is available to the meadow vole, it will compensate for the low nutritional value of the food by increasing the quantity of it that it ingests. This increase in food intake causes the gastrointestinal tract of the meadow vole to become larger, allowing the food to remain for a longer time in the animal's digestive system and giving it a longer period of time to absorb the few nutrients that are present.^[14] Being deprived of food for long periods of time can influence the meadow vole's reproductive rate, as the starved animals will not mate as often as well fed animals would.^[15]

Reproduction

A young Meadow Vole in the open.

The meadow vole can reproduce multiple times each year. Average females have between one and five litters in a year, producing about five pups in each litter.^[16] They become reproductively active only during a specific time of the year based on the length of the photoperiod. Meadow voles experience the greatest degree of reproductive activity during times when they are exposed to a long photo period of fourteen hours of light to ten hours of darkness.^[17] Their reproductive rates can also be reduced if they are deprived of food for long periods of time.^[18] Though meadow voles reproduce very frequently and produce many offspring, they have a relatively short life compared to other mammals. On average, a meadow vole living in its natural environment will live 154 days, less than one year.^[19] This short life span is not due to the results of natural aging or disease. In many cases, this early death is caused by predation. The small size of M. pennsylvanicus makes it an appropriate prey to many larger mammals. Common predators to the meadow vole are the red fox, Vulpes vulpes; the bob cat, Lynx rufus; and the coyote, Canis latrans^[20][21].^[22][23] The meadow vole has very few defenses against those animals which prey on them. The main method of escaping predators used by the meadow vole is to burrow into its underground tunnels or to hide among the dense grass in which it lives. Even if it picks up the scent of a predator, the meadow vole will remain in the same location if it has adequate plant cover.^[24] In environments where larger predators are present, meadow voles generally have a larger body size than meadow voles living in environments with predominantly smaller predators.^[25] Although meadow voles rarely live longer than a year in the wild, if taken into captivity—for reasons such as being kept as a lab test subject or as a pet—they can live for as long as three years^[26]).

Ecological importance

Similar to other small mammals, M. pennsylvanicus is very important to the environments in which they live.^[27] As previously mentioned, the meadow vole is prey for many larger animals and therefore it acts as a food source for those animals and an indirect food source for secondary predators.^[28] In addition to this important role, the meadow vole is also vital for dispersing mycorrhizal fungi. The meadow vole is also a major consumer of grass which enables it to disperse the nutrients contained within the grass by their feces.^[29] When an area experiences a major disturbance, such as a forest fire or a clear cutting project, the meadow vole is important to helping the ecosystem recover from these events.^[30] Due to the fact that the meadow vole lives in open areas,^[31] when large quantities of trees are removed it creates an environment that is favorable for the meadow vole. In the forest adjacent to an area that has been clearcut, very few meadow voles are found. In the newly opened area, the meadow vole is quite abundant.^[32] Because the meadow vole moves into these areas, it allows for a food source for other animals who otherwise would not be able to remain in the disturbed ecosystem.^[33]

The Meadow Vole has previously been used as a bioindicator to monitor chemical leakage around Love Canal and radiation releases in the aftermath of the Three Mile Island Accident.^{[citation needed]}

See also

• Gull Island Vole

Notes

References