Fossil Record: The size of the incisive foramina is used to help distinguish California voles from other species. In M. californicus, the foramina is wider and unconstricted, and the teeth are slightly larger than other species of vole that occur near California. It is possible M. californicus could have first appeared 1.8 million years before present in North America at the beginning of the Pleistocene, making it possibly one the first occurring in the Microtus.
Humboldtian (Northwestern California), Diablian (Central California), Californian (Valley and Eastern California), and San Bernardinian (Southern California) provinces exist in California. There are seventeen subspecies of M. californicus that occur in its region.
California voles communicate mostly through scent by depositing urine in areas of its runways as a tracking device. This tells the vole where it has been and who else inhabits a runway. Squeaks are also heard from adults during distress and young when communicating to the parent(s).
As with most other mammals, there is likely some visual communication as well.
Communication Channels: visual ; tactile ; acoustic ; chemical
Other Communication Modes: scent marks
Perception Channels: visual ; tactile ; acoustic ; chemical
These voles are quite common and so are not a big conservation concern. Local abundances can vary from year to year, but overall the population cycle seems stable. However, because thes voles are so important to their ecosystem, it is worthwile to keep an eye on their population cycles and habitat availability, so that other species which depend upon them for food, and whose population status may be less secure, are safeguarded.
US Migratory Bird Act: no special status
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
During peak population times, numbers of voles are said to exceed to the hundreds per acre, and up to a thousand per hectare, causing crop problems in areas where farms coincide with vole habitat.
Negative Impacts: crop pest
Although there is apparently no direct benefit of this species for humans, it should be noted that without this keystone species, many of the larger animals that people enjoy watching, such as hawks, kestrels, coyotes and foxes, would not be able to exist at such high densities, and therefore would be a much less visible part of local ecosystems.
With their potential to reproduce rapidly, these voles are prey for many carnivore species. They form an important link in food webs. these voles also are hosts to many species of parasites.
Ecosystem Impact: keystone species
Commensal/Parasitic Species:
M. californicus is herbvivorous and eat mostly grasses and roots, but also relies on sedges, fruits and forbs in certain areas. In the winter, the vole eats mostly roots and underground plant parts. Grain will also be eaten when available.
Plant Foods: leaves; seeds, grains, and nuts; fruit
Primary Diet: herbivore (Folivore , Frugivore , Granivore ); coprophage
Microtus californicus occurs along the Pacific Coast of North America, from central Oregon southward to northern Baja California. It occurs in the woodlands, shrublands and grasslands of these areas.
Biogeographic Regions: nearctic (Native )
California voles inhabit areas of broad-leaved chaparral, oak woodlands, and grasslands along the Pacific Coast in northern Baja California to central Oregon. This species has a restricted distribution, which is possibly due to relic populations. It seems to utilize unusual habitats in California compared to other species of voles throughout the North American continent. Marshy ground, saltwater and freshwater locations, wet meadows, coastal wetlands and dry, grassy hillsides are the preferred macrohabitats of this species.
California voles are semifossorial. Their microhabitat consists of burrows, grass runways, and earth tunnels where piles of grass cuttings and fresh vegetation are often found. Piles of feces are also found in the runways.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: desert or dune ; savanna or grassland ; chaparral
Wetlands: marsh
Other Habitat Features: agricultural ; riparian
A successful lifespan for a vole will be up to a year, but the average lifespan is only a few months.
Typical lifespan
Status: wild: 1 to 12 months.
M. californicus present a lot of variation in size depending upon where they are found. Subspecies found in the south of the species range can be much larger than those found in the north.
In northern California, the total length veries between 139 ans 207 mm, of which only 39 to 68 mm is contributed by the tail. Males weigh between 33 and 81 g, averaging 52 g, and females can weigh between 30 and 68 g, averaging 47 g.
California voles are sexually dimorphic with the males being six percent longer and eleven percent heavier than females.
The coat of these animals is buffy brown, grayish brown or dark brown (blackish toward coast, reddish in desert) colored on top, with a reddish tinge down the middle of the back. The underside is blue-gray to white. The tail is bi-colored. The feet are pale, and the eyes are dark brown to black. M. californicus has 8 mammae.
This species can be distinguished from other voles by the following characteristics:
Microtus montanus occurs at higher elevations;
M. longicaudus is longer and its tail more bicolored;
M. townsendii has different cranial and dental features; and
M. oregoni is smaller and has only 5 toe pads.
Range mass: 38 to 108 g.
Range length: 139 to 214 mm.
Sexual Dimorphism: male larger
Other Physical Features: endothermic ; bilateral symmetry
Voles spend as little time exposed to the surface as possible. Underground tunnels are commonly used as are runways throughout tall grasslands. Unfortunately for the voles, the urine they use to communicate to each other is the way their diurnial predators track them and determine vole density. Through the raptors ability to see ultraviolet light, the florescent urine shows up in the runways and directs the predator to the prey's location. This could also explain how raptors are able to locate their vole prey even after population crashes.
There are a great number of vole predators, including coyotes, kestrels, hawks, weasles, kits, owls, snakes, herons, egrets, and ferrel cats. Because of their rapid reproduction and periody high population densities, these voles are a keystone prey species.
Known Predators:
California voles seem mostly monogomous when populations aren't too dense. Dense populations or populations with unbalanced sex ratios will display polygynous traits. In these populations, males defend territories where grass is the staple diet, and females defend areas where fruits and forbs are the primary food source.
When polygyny is the prevailing mating system, females tend to have neighboring territories with their sisters and dispersing males may have little or no contact with close relatives.
Suppression of sexual maturation on the natal home range by the presence of the mother occurs. Kin recognition has little influence on inhibiting inbreeding, even in monogamous populations.
Adult males will cannibalize young that are not theirs. Females will also abort their litters if exposed to the phermones produced by unfamiliar males.
Mating System: monogamous ; polygynous
Ovulation in M. californicus is induced by copulation. This species experiences a post-partum estrus, and breeding can occur within fifteen hours after young are born. This allows up to 4 or 5 litters a season.
The breeding season is somewhat variable throughout the range of this species. Germination of annual grasses in the fall seems to initiate reproduction in some popultions. In other populations, where the climate is very Mediterranean, reproduction begins near the time of the first rains, and ends when the hot summer dries out the vegetation. In coastal populations, where the grasses stay green all year, and temperatures are mild, breeding can occur thorughout the year.
The gestation is twenty-two days. Litters of 1 to 11 young can be roduced, but the average is 4 or 5 young. Perennial grassland populations average about two embryos less than those in annual and mixed annual-perennial grassland populations. Young are altricial and weigh approximately 2.5g at birth. The pups are quickly weaned at two weeks old.
Females reach reproductive maturity by three weeks old, and the male at five weeks. Under some conditions, males can mature more rapidly, reaching sexual maturity by about 25 days of age. Sexual maturity can be supressed by the presence of the parents on the natal range. This allows the species to rapidly colonize when population densities are low, but to limit reproduction somewhat when populations are very dense.
Microtus species in general, appear to have a fairly plastic reproductive biology where the emphasis seems to be on the ability to produce the correct response (phenotypic) given the ecological conditions in which the population finds itself. Populations experience cyclic and annual fluctuations. The population typically grows for three to four years then declines rapidly in mild, temperate areas. In strongly seasonal habitats, the growth phase is two to five years.
Breeding interval: These voles can breed every three weeks under good conditions.
Breeding season: The breeding season seems to heavily rely on the wet season in non-coastal parts of California. In coastal populations, breeding is aseasonal.
Range number of offspring: 1 to 11.
Range gestation period: 22 (high) days.
Average weaning age: 2 weeks.
Average time to independence: 2 weeks.
Range age at sexual or reproductive maturity (female): 21 (low) days.
Range age at sexual or reproductive maturity (male): 25 to 42 days.
Key Reproductive Features: iteroparous ; seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; induced ovulation ; fertilization ; viviparous ; post-partum estrous
As in all mammals, the female provides the young with milk for the duration of nursing. Although the young are altricial at birth, they grow quickly. Weaning occurs when the young are abut two weeks old.
In polygynous systems, females are the primary care givers, with neighboring territories being occupied by their sisters. In monogamous systems, males will participate in brood care. In these mating systems, males participate in parental care by gathering nesting materials and retreiving nestlings. Both males and females will display territorial traits, which helps to protect the young from intruders.
Nests are made with dried grasses and forbs and are located under logs or boards or under the earth's surface a few centimeters.
Parental Investment: altricial ; pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Male, Female)
The California vole (Microtus californicus) is a type of vole[2] which lives throughout much of California and part of southwestern Oregon. It is also known as the "California meadow mouse", a misnomer as this species is a vole, not a mouse. It averages 172 mm (6.8 in) in length although this length varies greatly between subspecies.
The California vole is a medium-sized vole, and a typical member of its group in appearance. Males range from 152 to 196 mm (6.0 to 7.7 in) in head-body length, with a 42 to 58 mm (1.7 to 2.3 in) tail. Females are significantly smaller at 149 to 182 mm (5.9 to 7.2 in) in length with a 38 to 53 mm (1.5 to 2.1 in) tail. Males weigh from 41 to 81 g (1.4 to 2.9 oz), and females from 36 to 63 g (1.3 to 2.2 oz).[3] Variation between different subspecies, though, is considerable, with the southern subspecies tending to be larger than those found further north.[4]
The body is covered with cinnamon to tawny olive fur, ticked with occasional darker hairs, and fading to a medium grey on the underside. The tail is black above and grey below. The whiskers and feet are grey in color, with a patch of white fur near the anus.[3] Between subspecies, those native to more highland habitats tend to be more reddish in color, and those in marshier environments tend to be darker. Males have a pair of scent glands on the hips, which are used to mark their trackways. Females have four pairs of teats, two in the chest, and two closer to the groin.[4]
The California vole is found from El Rosario in Baja California in the south, through much of California and as far as Eugene, Oregon in the north. It is, however, absent from most of the deserts of southeastern California and from the extreme northeastern and northwestern corners of the state. It inhabits a range of different grassland habitats, from wet coastal marshland to dry uplands and savannah.[5]
Seventeen subspecies are currently recognized,[4] some of which are protected.[6] They include:
The California vole is herbivorous, feeding mainly on grasses and sedges, supplemented by other flowering herbs. Preferred foods include wild oats, ryegrass, and brome grass, although all of these are introductions from Europe, and therefore cannot represent the animal's original diet.[7] They can become an agricultural pest, causing widespread damage especially to fields of artichokes, but also to crops such as alfalfa, potatoes, and asparagus.[4]
Because the California vole is relatively common and widespread, it has numerous natural predators, including hawks, owls, egrets, long-tailed weasels, coyotes, skunks, mountain lions and garter snakes.[4]
California voles are crepuscular or nocturnal. However, they spend much of their time below ground, using burrows connected by above-ground runways they use to find food. Home ranges are relatively small, with the animals rarely venturing far from their burrows; averages of 103 square metres (1,110 sq ft) for males and 68 square metres (730 sq ft) for females have been reported. The larger ranges of males overlap with the ranges of several nearby females, but they are generally aggressive only towards other nearby males, clawing and biting any intruders.[8] Although they also sometimes use abandoned gopher tunnels, burrows dug by the voles themselves are blind-ending and range from 1.5 to 12 m (4.9 to 39.4 ft) in length. The voles construct nests of dried grass within their burrows; these have a single entrance, and are typically between 7 and 15 cm (2.8 and 5.9 in) below the surface.[9]
The voles are active above ground primarily to find food, reaching the seeds on high grasses by standing on their hind legs and clipping the stems with their teeth. They often carry the food back to their burrow to eat it, although they do not hoard food or hibernate through the winter. California voles are often found in groups of a single male, one or more females, and a number of young, and the male may assist the female in construction of her nest before she gives birth. California voles are reasonably strong swimmers, and may use this tactic to attempt to escape from predators.[4]
California voles are able to breed almost year-round, although most breeding occurs during the middle of the wet season, from March to April. Males may breed with more than one female, although the species is not as strongly polygynous as some other voles. Copulation can be prolonged and repeated, and is followed by formation of a copulatory plug and by induced ovulation. Gestation lasts three weeks and results in the birth of up to 10 young, with four or five being most common. The female is ready to breed again with 15 hours of giving birth, and may give birth to several litters over the course of her life.[4]
The young are born hairless and blind, weighing an average of 2.8 g (0.099 oz). They begin to grow fur within five days of birth, and their eyes open at 9 days, although they are capable of sensing light before this. The young are weaned at around two weeks of age, and have a full set of adult teeth by three weeks. Females reach sexual maturity after as little as three weeks, while males become sexually mature after six weeks.[4] The lifespan is correspondingly short, with individuals living for less than a year, even in the absence of predators.
Fossils of members of the genus Microtus are known from California as far back as 1.2 million years ago, although it is unclear whether these represent California voles specifically, or a related, possibly extinct, species.[10] Genetic evidence suggests the closest extant relative of the California vole is most likely the Mexican vole, Microtus mexicanus, and the species is known to be able to produce infertile hybrids with other closely related species, such as the montane vole. Indeed, matings between northern and southern subspecies of California vole do not always produce fertile offspring, with male hybrids in particular typically being infertile. This may indicate some of the subspecies are in the process of diverging into separate species, and it has even been proposed that the California vole may already represent two different species.[11]
The California vole (Microtus californicus) is a type of vole which lives throughout much of California and part of southwestern Oregon. It is also known as the "California meadow mouse", a misnomer as this species is a vole, not a mouse. It averages 172 mm (6.8 in) in length although this length varies greatly between subspecies.
