138.

California Vole

Microtus californicus

French: Campagnol de Californie / German: Kalifornien-Wihlimaus / Spanish: Topillo de California

Other common names: Amargosa Vole, California Meadow Mouse

Taxonomy. Arvicola californica [sic] Peale, 1848, vicinity of San Francisco Bay, California, USA. Restricted by R. Kellogg in 1918 to “ probably at San Francisquito Creek, near Palo Alto.”

Seventeen subspecies are recognized.

Subspecies and Distribution.

M.c.californicusPeale,1848—knownfromafewlocalitiesfromWalnutCreekStoPozo,WCCalifornia,USA.

M.c.aequivocatusOsgood,1928—knownfromafewlocalitiesfromSanTelmoStothevicinityofElRosario,NWBajaCalifornia,Mexico.

M.c.aestuarinusKellogg,1918—mostofCentralValleyofCalifornia,USA.

M.c.constrictusBailey,1900—NWCalifornia,withdistributionallimitsnearEureka,FairOaks,Cuddeback,andCapetown.

M.c.eximiusKellogg,1918—fromWCOregonSthroughNCCaliforniatonearlytheSanFranciscoBay,USA.

M.c.grinnelliHuey,1931—knownonlyfromthetypelocalityatSangredeCristoinValleSanRafael,ontheWbaseoftheSierraJuarez,NCBajaCalifornia,Mexico.

M.c.halophilusvonBloeker,1937—verysmallrangenearthemouthofElkhornSlough,MossLanding,andSeaside,WCCalifornia,USA.

M.c.huperuthrusElliot,1903—knownfromafewlocalitiesintheSierradeSanPedroMartir,NCBajaCalifornia,Mexico.

M.c.kernensisKellogg,1918—extremeSCentralValleyMts,extremeSSierraNevada,andfloorofWMojaveDesert,SECalifornia,USA.

M.c.mariposaeKellogg,1918—WfoothillsofSierraNevada,ECalifornia,USA.

M.c.mohavensisKellogg,1918—knownonlyfromnearOroGrandeandVictorvilleinSanBernadinoCounty,SCCalifornia,USA.

M.c.paludicolaHatfield,1935—arestrictedrangeborderingtheSedgeofSanFranciscoBay,WCCalifornia,USA.

M.c.sanctidiegiKellogg,1922—SWCalifornia,fromLosPinosStotheborderwithMexico,andextremeNBajaCalifornia,Mexico;alsointroducedontoSanClementeI.

M.c.sanpabloensisThaeler,1961—averysmallrangelimitedtonearthesaltmarshSanPabloCreekontheWsideofSanFranciscoBay,WCCalifornia,USA.

M.c.scirpensisBailey,1900—Tecopa,InyoCounty,SECalifornia,USA.ExtinctfromtypelocalityontheAmargosaRivernearshoshone.

M.c.stephensivonBloeker,1932—alimitedrangenearPointMugu,SunsetBeach,andPlayadelRey,SWCalifornia,USA.

M. c. vallicola Bailey, 1898 — Owens and Deep Springs valleys, E California, USA.

Descriptive notes. Head-body 111-138 mm, tail 38-58 mm, hindfoot 18-24 mm; weight 47-1 g (males) and 43-4 g (females). Males average 6% longer and 11% heavier than females, and individuals in northern populations tend to be smaller than those in southern populations. The California Vole is medium-sized, with tawny olive to cinnamon brown dorsum and long dark overhairs. Venteris gray, often with white-tipped hair. Tail is bicolored, brown or black above and grayish below. M* has four closed triangles. Incisive foramina are widest in middle and rounded at both ends. Six plantar tubules are on feet, and males have side glands on their hips (instead of on their sides as in several other species of Microtus). Diploid number is 2n = 52-54.

Habitat. Grass-dominated habitats, including grasslands with mix of forbs and short woody shrubs, fresh-water and coastal salt marshes, arid uplands, and oak ( Quercus, Fagaceae) savanna. Perennial grasslands (e.g. Elymus cinereus, Poaceae) are favored over annual grasslands (e.g. Bromus rigidus, Poaceae). California Voles occur in wet meadows at sea level to the high-elevation meadows of the Sierra de San Pedro Martir at the southern extreme of its distribution in Mexico.

Food and Feeding. Wild California Voles eat grasses, sedges, and forbs and subsist primarily on seeds and roots during dry summers. They prefer grasses (e.g. Avena fatua, Lolium multiflorum, and B. nigidus, Poaceae), feeding especially on grass seed heads and upper stems in summer. In captivity, they ate up to ¢.85% of their body mass daily in fresh alfalfa ( Medicago sativa, Fabaceae) and A. fatua. California Voles can damage crops including artichokes, alfalfa, potatoes, wheat, and asparagus.

Breeding. California Voles can breed almost year-round (270-320 days), but most breeding occurs during middle of the wet season in March-April, because green vegetation stimulates breeding. They are thought to be less polygynous than other voles. Gestation lasts ¢.3 weeks. Litters usually have 4-5 young, butlittersizes vary geographically, seasonally, and with female age and density. Young average 2-8 g at birth and are blind, deaf, and hairless; they are weaned at 2-3 weeks.

Activity patterns. California Voles are active primarily at night but also in early morning and evening. They build burrows and use abandoned gopher burrows, with much of their daily activity underground, except when foraging and defecating aboveground.

Movements, Home range and Social organization. Excursions by California Voles aboveground averaged seven minutes during the day and one minute at night. Burrows can have grass-lined nests, and burrow entrances can be connected to each other, old gopher burrows, or other safe places via aboveground runways. These runways are typically used by one family group. Average home ranges of males are larger (103 m?) than females (68 m*). Male home ranges tend to overlap home ranges of multiple females. California Voles often form family groups of a single male, one or more females, and young. In these groups, the male might assist the female in construction of her nest before she gives birth. Populations in environments with less seasonal variability have relatively stable densities over time, but populations in regions that experience greater seasonality have 3-5 year population fluctuations.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Subspecies grinnelli, huperuthrus, and scirpensis are of conservation concern.

Bibliography. Batzli & Pitelka (1971), Conroy & Neuwald (2008), Cudworth & Koprowski (2010), Heske (19874, 1987b), Heske & Lidicker (1999), Heske & Ostfeld (1990), Kellogg (1918), Lidicker & Ostfeld (1991), Patton & Conroy (2017), Pearson (1960).