Voles are small rodents that are relatives of lemmings and hamsters, but with a stouter body; a longer, hairy tail; a slightly rounder head; smaller eyes and ears; and differently formed molars (high-crowned with angular cusps instead of low-crowned with rounded cusps). They are sometimes known as meadow mice or field mice. Vole species form the subfamily Arvicolinae with the lemmings and the muskrats. There are approximately 155 different vole species.
Description Voles are small rodents that grow to 8–23 cm (3–9 in), depending on the species. Most voles do not exceed 16 months in age in the wild, though in captivity they may live as long as three years. The vole mating season spans about half the year (from spring to fall) with litters produced monthly. Each litter is usually made up of two to nine offspring. Gestation lasts for three weeks and the young voles reach sexual maturity in a month. As a result of this biological exponential growth, vole populations can grow very large within a short time. One mating pair can produce 100 offspring every year. Voles outwardly resemble several other small animals. Moles, gophers, mice, rats and even shrews have similar characteristics and behavioral tendencies. Voles thrive on small plants yet, like shrews, they will eat dead animals and, like mice and rats, they can live on almost any nut or fruit. In addition, voles target plants more than most other small animals, making their presence evident. Voles readily girdle small trees and ground cover much like a porcupine. This girdling can easily kill young plants and is not healthy for trees and other shrubs. Voles consume their own body weight in plant material every 24 hours. Their most noticeable activity is burrowing under plants where they can access nutritious bulbs and root systems. They also eat herbaceous material and may eat away until the plant is dead. The presence of large numbers of voles is often identifiable only after they have destroyed a number of plants. However, like other burrowing rodents, they also play beneficial roles, including dispersing nutrients throughout the upper soil layers.
Predators Many predators eat voles, including martens, owls, hawks, falcons, coyotes, bobcats, foxes, raccoons, squirrels, snakes, weasels, domestic cats and lynxes. Vole bones are often found in the pellets of the short-eared owl, the northern spotted owl, the saw-whet owl, the barn owl, the great gray owl, and the northern pygmy owl. In the summer of 2024, biologists and other scientists at UC Davis first observed California ground squirrels actively hunting voles.
Lifespan
The average lifespan for smaller species of vole is three to six months, and they rarely live longer than 12 months. Larger species, such as the European water vole, live longer and usually die during their second, or rarely their third, winter. As many as 88% of voles are estimated to die within the first month of life.
Genetics and sexual behavior The prairie vole is a notable animal model for its monogamous social fidelity, since the male is usually socially faithful to the female, and shares in the raising of pups. The woodland vole is also usually monogamous. Another species from the same genus, the meadow vole, has promiscuously mating males, and scientists have changed adult male meadow voles' behavior to resemble that of prairie voles in experiments in which a viral vector was used to increase a single gene's expression within a particular brain region. The behavior is influenced by the number of repetitions of a particular string of microsatellite DNA. Male prairie voles with the longest DNA strings spend more time with their mates and pups than male prairie voles with shorter strings. However, other scientists have disputed the gene's relationship to monogamy, and cast doubt on whether the human version plays an analogous role. Physiologically, pair-bonding behavior has been shown to be connected to vasopressin, dopamine, and oxytocin levels, with the genetic influence apparently arising via the number of receptors for these substances in the brain; the pair-bonding behavior has also been shown in experiments to be strongly modifiable by administering some of these substances directly. Voles have a number of unusual chromosomal traits. Species have been found with 17 to 64 chromosomes. In some species, males and females have different chromosome numbers, a trait unusual in mammals, though it is seen in other organisms. Additionally, genetic material typically found on the Y chromosome has been found in both males and females in at least one species. In another species, the X chromosome contains 20% of the genome. All of these variations result in very little physical aberration; most vole species are virtually indistinguishable. In one species, the creeping vole Microtus oregoni, it was discovered the Y chromosome has been lost entirely; the male-determining chromosome is actually a second X that is largely identical to the female X, and both the maternally inherited and male-specific sex chromosomes carry vestiges of the ancestral Y. This is quite unusual in mammals, as the XY system is fairly stable across a number of mammal species.
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