Vole Biology

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Reproduction

Voles may breed throughout the year, but most commonly in spring and summer. Voles typically have 1 to 5 litters per year, though in laboratory settings, voles have produced up to 17 litters annually. Litter sizes range from 1 to 11, but average 3 to 6. The gestation period is about 21 days. Young are weaned by the time they are 21 days old. Females mature in 35 to 40 days. The lifespan of voles are short, ranging from 2 to 16 months.

Population levels generally peak every 2 to 5 years, though the cycles are not predictable. During population irruptions, densities of voles have risen to 4,000 voles per acre! Dispersal, food quality, climate, predation, physiological stress, and genetics influence the levels of the populations. Densities of long-tailed voles in California ranged from 2 to 7 voles per acre and in New Mexico ranged from 8 to 49 voles per acre. Prairie voles averaged 15 per acre in prairie, 52 per acre in bluegrass, and 99 per acre in alfalfa. Another population ranged from 1 to 14 per acre over 3 years in western mixed prairie. Variability in the densities of meadow voles was noted in Ontario, Canada where a population had 32 to 162 per acre while a population in Illinois had 2 to 6 individuals per acre. Other populations show similar variability.

Nesting Cover

Nests of voles vary among species and within the same species. Prairie voles establish nests aboveground or up to 18 inches belowground. Pine voles typically establish complex burrows up to 4 feet belowground.

Behavior

Voles are active day and night, year-round. They do not hibernate. Home ranges usually are ┬╝ acre or less but they vary with season, population density, habitat, food supply, and other factors. Voles are semi-fossorial and construct many tunnels and surface runways with numerous entrances to a burrow. A single burrow system may contain several adults and young. Many species of voles are excellent swimmers. The climbing ability of voles varies. Long-tailed voles, for example, climb well, while pine voles do not.

Habitat

Voles occupy a wide variety of habitats. They prefer areas with heavy ground cover of grasses, forbs, and litter. When 2 species are found together in an area, usually they occupy different niches. Voles use habitats modified by humans such as orchards, wind-breaks, and cultivated fields, especially when vole populations are high. Below is a discussion of the common habitats of the 7 species of voles described in this module.

  1. Prairie voles are the most common species of vole in the grasslands of the Great Plains. They are found in habitats such as old fields, marshlands, and grass prairies. When in association with meadow voles, prairie voles generally are in drier habitats.
  2. Meadow voles prefer wet meadows and grassland habitats in the northern US and Canada. When associated with prairie voles, meadow voles generally are in moister habitats.
  3. Long-tailed voles are found in a wide variety of habitats (sagebrush grasslands, forests, mountain meadows, and stream banks) in the western US and Canada.
  4. Pine voles prefer heavy ground cover in deciduous and pine forests, abandoned fields, and orchards in the eastern US. 
  5. Montane voles prefer alpine meadows, dry grasslands, and sagebrush grasslands in mountainous regions of the western US. They typically avoid forests. When in association with meadow voles, montane voles generally are in drier habitats.
  6. Oregon voles prefer forbs and grasses in burned or clear-cut areas in northern California, Oregon, and Washington.
  7. California voles inhabit chaparral woodland and shrub land of California. They are found in wet and well-drained areas.

Food Habits

Voles eat a variety of plants, most frequently grasses and forbs. In late summer and fall they store seeds, tubers, bulbs, and rhizomes. They primarily eat bark in fall and winter and eat crops during spring and summer, especially when densities of voles are high. Occasional food items include snails, insects, and remains of animals.