Voles are small, stout-bodied rodents often mistaken for mice or shrews. They are distinguishable by their short tails, small eyes, barely visible ears, and a blunt muzzle. The United States is home to approximately 23 native species of voles, which belong to the genus Microtus. These herbivores are found across North America and play a role in various ecosystems due to their high reproductive rate.
Widespread Species and Their General Range
The Meadow Vole, Microtus pennsylvanicus, has the most extensive range, covering the northern half of the US from the Atlantic coast westward. This distribution continues through much of Canada and extends into Alaska. The western boundary of its continuous territory is generally marked by the Rocky Mountains, though isolated populations can be found further west.
The Prairie Vole, Microtus ochrogaster, primarily inhabits the central region of the country. This species is found across the Midwest, reaching from northeastern New Mexico up to northern Alabama. Its range encompasses the Great Plains, making it the most frequently encountered vole in prairie ecosystems. The Prairie Vole’s territory often overlaps with the Meadow Vole, but it typically occupies the drier habitats within this shared area.
Specialized Voles of Specific US Regions
Many voles are restricted to specific ecological zones. The Montane Vole, Microtus montanus, is confined to the mountainous regions of the western US. Its range spans high-elevation areas, including the eastern Sierra Nevada slopes in California, the mountain meadows of Oregon, and the western half of Colorado. This species is adapted to alpine and dry grasslands that characterize the high-altitude terrain.
In the far north, the Tundra Vole, Microtus oeconomus, occupies the extreme northwestern part of the continent, predominantly throughout Alaska. This species has a circumpolar distribution and is the northernmost vole in North America, found in the Arctic coast regions and certain Aleutian Islands.
The Pine Vole, now often called the Woodland Vole (Microtus pinetorum), is concentrated in the eastern United States. This small species is most common across the Southeast and East, generally found in deciduous or mixed forests. Its range extends through most of the eastern states, associated with forested, often agricultural, areas. The California Vole (Microtus californicus) is the most common vole throughout the Central and Owens valleys and the coastal ranges of California.
Defining Vole Habitats
Vole distribution is strongly influenced by the specific environmental characteristics of a location. All species prefer areas with dense ground cover, which provides protection from predators and facilitates movement. This cover often consists of tall grasses, sedges, thick leaf litter, or weeds.
Moisture content in the soil is another defining factor, as voles construct extensive burrow systems for nesting, food storage, and travel. Species like the Meadow Vole are considered semi-fossorial, creating conspicuous surface runways beneath the vegetation, especially in low-lying wetlands and open grasslands. These surface trails are about one to two inches wide.
Other species, such as the Pine Vole, are primarily fossorial, living underground in complex tunnel networks. These tunneling voles prefer loose, sandy, or loam soils that are easier to excavate than heavy, wet clay. The specific habitat requirements, such as a deep humus layer or dense perennial grasses, often determine which species can successfully establish a stable population in a given locale.