Creeping vole
Template:Short description Template:Speciesbox
The creeping vole (Microtus oregoni), sometimes known as the Oregon meadow mouse, is a small rodent in the family Cricetidae. Ranging across the Pacific Northwest of North America, it is found in forests, grasslands, woodlands, and chaparral environments. The small-tailed, furry, brownish-gray mammal was first described in the scientific literature in 1839, from a specimen collected near the mouth of the Columbia River. The smallest vole in its range, it weighs around Template:Cvt. At birth, they weigh Template:Cvt, are naked, pink, unable to open their eyes, and the ear flaps completely cover the ear openings. Although not always common throughout their range, there are no major concerns for their survival as a species.
Taxonomy
The animal was described in 1839 by John Bachman.Template:Sfn The original scientific name was Arvicola oregoni with a common name of the Oregon meadow mouse.Template:Sfn The type specimen was an older male collected November 2, 1836 near the mouth of the Columbia River in Oregon.Template:Sfn The specimen had been submitted to Bachman for review by John Kirk Townsend.Template:Sfn Subsequent authorities state that it was collected at Astoria, Oregon, which is at the mouth of the Columbia River.Template:Sfn In 1857, Baird placed Arvicola oregoni in a section Chilotus of the subgenus Arvicola of the genus Arvicola.Template:Sfn In 1874, PNAS paper, Coues reclassified Chilotus as a subgenus and refers to the animal as Arvicola (Chilotus) oregonus.Template:Sfn[1] Miller subsequently reclassified the animal in the genus Microtus and maintained the subgenus Chilotus.Template:Sfn This was the first reference to the animal under its current scientific name Microtus oregoni.Template:Sfn It was subsequently reclassified to the subgenus Mynomes,Template:Sfn though the American Society of Mammalogists lumps that subgenus's species in with subgenus Pitymys.[2]
Description
| Skull dimensionsTemplate:Sfn | ||
|---|---|---|
| Minimum | Maximum | |
| Basal length | Template:Cvt | Template:Cvt |
| Nasal length | Template:Cvt | Template:Cvt |
| Zygomatic breadth | Template:Cvt | Template:Cvt |
| Mastoid breadth | Template:Cvt | Template:Cvt |
| Upper molar alveolus | Template:Cvt | Template:Cvt |
On average, creeping voles weigh around Template:Cvt with a reported range of Template:CvtTemplate:Sfn The average length is around Template:Cvt, with a range of around Template:CvtTemplate:Sfn Compared to other voles within their geographic range, they are the smallest.Template:Sfn They have smaller eye opening (around Template:Cvt in diameter) compared to other voles that share the same geographic range (sympatric) or have adjacent ranges (parapatric).Template:Sfn There are other distinguishing features of the roots and enamel of the molar teeth that help in differentiation.Template:Sfn Unlike other voles in the range, only the creeping vole and the (much larger) water vole have five plantar tubercles on the hindfeet.Template:Sfn
They are Pentadactyl, although the pollex is reduced in size and lack a claw.Template:Sfn They walk with their feet planted firmly on the ground (plantigrade locomotion).Template:Sfn The foot pads have a moderate amount of fur.Template:Sfn
The fur markings are plumbeous to a dark brown or black.Template:Sfn There are sometimes yellowish hair markings as well.Template:Sfn The underside fur markings tend to be lighter beige to whitish.Template:Sfn The tail may be gray to black and often lighter below.Template:Sfn
Creeping voles have a relatively short tail, measuring less than 30% their total body length.Template:Sfn They have short ears, which are nearly hairless, though a few black hairs present.Template:Sfn They protrude just slightly from the fur around the head.Template:Sfn They have eight mammae, with two pairs present in each of the pectoral and inguinal regions.Template:Sfn
The skull of the creeping vole has a low, flat profile, with a long and slender snout.Template:Sfn The zygomatic arches are somewhat delicate.Template:Sfn The incisive foramen is short and wide, but not so much as to be a distinguishing feature.Template:Sfn They have small molars.Template:Sfn
Distribution and habitat
Creeping voles are found in British Columbia in Canada and in Washington, Oregon and northern California, in the United States.Template:Sfn They are found as far north as Port Moody, British Columbia and as far south as Mendocino City, California.Template:Sfn The western range in Washington extends east to Mount Aix, Lake Chelan, and Signal Peak.Template:Sfn The range in Oregon extends east to the north base of Three Sisters and to Crater Lake.Template:Sfn There are variable reports as to their occurrence in the Willamette Valley of Oregon.Template:Sfn In California, they are found as far east as Beswick and South Yolla Bolly Mountain.Template:Sfn
They are found in coniferous forests and woodlands, grasslands, and chaparral.Template:Sfn They are found at sea level through altitudes of nearly Template:Cvt.Template:Sfn They are more populous in areas of disturbance than virgin forests.Template:Sfn They are burrowing animals and will also use fallen logs, other debris, and patches of grass for cover.Template:Sfn The burrows are shallow.Template:Sfn They are found in moist forests along the coast, but may do well in drier areas.Template:Sfn
It is suspected that ancestral voles migrated from Eurasia 1.2 million years ago.Template:Sfn However, no Pleistocene-era fossils of creeping voles have been identified.Template:Sfn
Behavior and ecology
Creeping voles establish nests of dry grass in protected areas, such as under logs.Template:Sfn The breeding season varies by latitude, but is mainly March to September in Oregon and British Columbia.Template:Sfn Gestation lasts around 23 days. Each litter bears three to four young and the females may produce four or five litters a year.Template:Sfn The naked, pink newborn young weigh around Template:Cvt.Template:Sfn Their eyes are closed and skin flaps cover the ear openings.Template:Sfn
Creeping voles are primarily nocturnal, though they are sometimes active during the day.Template:Sfn They are herbivorous, probably eating forbs and grasses, as well as fungi.Template:Sfn
Genetics
Creeping vole females have XO sex chromosomes, while males have XY. Evolutionary geneticists have investigated these sex chromosomal features of creeping voles. A models for the evolution of creeping vole sex chromosomes was published by researchers from the University of Edinburgh in 2001.Template:Sfn Recently, it was discovered the Y chromosome has been lost, the male-determining chromosome is a second X that is largely homologous 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.[3]
Conservation status
Although it is not widely distributed and not always common, the creeping vole is listed as "Least Concern" by the IUCN Red List.Template:Sfn The justifications for the listing are the lack of major threats, the stability of populations, and the adaptability of the animal to environmental changes.Template:Sfn Treatment of Douglas-fir plantations with herbicides in British Columbia did not affect creeping vole populations.Template:Sfn No conservation concerns are raised, since there are thought to be sufficient areas of protected habitat within its range.Template:Sfn NatureServe lists the species as secure within its range.Template:Sfn
References
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Footnotes:
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