California Vole, Microtus californicus

The California vole (Microtus californicus) can be found throughout California, and in certain parts of Oregon. Another name for this vole is the California meadow mouse. It is not found in most of the desert regions of California or in the northwestern corners. It prefers to live in the dry uplands of the savannah and marshlands. There are seventeen subspecies of this vole.

The California vole is typical in appearance to its species. It is medium sized, and can reach a body length of up to 7.7 inches, with a tail length of up to 2.1 inches. The average weight of this vole varies with sex, with females weighing 1.3 to 2.2 ounces and males weighing 1.4 to 2.9 ounces. Sizes will vary between subspecies, depending on their location. The fur can be colored olive brown to a reddish brown and may have darker hairs peppered throughout. The underbelly fades to grey. The voles’ feet and whiskers are grey as well.

California voles are considered nocturnal or crepuscular, spending twilight hours awake.  Although they do spend time outside of their den, they use tunnels within the burrow to search for food above ground, and will also use paths above ground that are connected to entrances. Sometimes, the voles will use abandoned gopher burrows, but prefer to dig their own. Burrows can reach a size of up to thirty-nine feet in length. The nest is made from dried plant material, and has only one entrance. The depth of the nest can vary from 2.8 inches and 5.9 inches below the ground, and male voles may help the females construct this nest before birth. Groups of one male, one or more females, and their young will inhabit these burrows.

These voles do not store food or hibernate through the winter. Most of the time, they will gather food and take it back to the burrow to eat. The diet of the California vole consists mainly of grasses and sedge material, but they will also eat herbs and seeds. California voles are known to swim, and it is though that this is a defense tactic to avoid predators including snakes, owls, hawks, coyotes, and skunks.

Typically, breeding will occur between the months of March and April, although California voles are able to reproduce year round. Males are slightly polygamous and may breed with numerous females, but this does not occur as much as it does with other species of voles. Females can have a few litters within their lifetime, and each will usually consist of four to five young. Each baby can weigh a meager .09 ounces when born, and is blind and hairless. Within five days of age, they will start to grow fur and can see at nine days. Weaning occurs at approximately two weeks. The lifespan of the California vole is relatively short. They may live less than a year, even with limited predators.

Fossils of the California vole date back to around 1.2 million years ago. It is unknown whether the fossils are of modern voles or an extinct version of voles. Research asserts that the closest relative of the California vole may be the Mexican vole, which has been known to breed with highly similar subspecies of voles. Breeding between closely related species can cause infertile hybrids, but it has been suggested that the California vole may be a product of this type of breeding.

Image Caption: Microtus californicus, San Luis Obispo County, California. Credit: Jerry Kirkhart/Wikipedia(CC BY 2.0)