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Microtus montanus

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Montane Vole
(Microtus montanus)
Range
Taxonomic classification
Order:Rodentia
Suborder:Supramyomorpha
Infraorder:Myomorphi
Superfamily:Muroidea
Family:Cricetidae
Subfamily:Arvicolinae
Tribe:Microtini
Genus:Microtus
Subgenus:Pitymys
Binomial details
Microtus montanus (Peale, 1849)
Other resources
Full taxonomic details at MDD

Description

From Sera & Early (2003): "Upper body is some shade of brown, often with a buffy or gray wash, with a mixture of black-tipped hairs. Sides are paler and more buffy than upper body, and venter is white to gray, sometimes washed with buffy. Tail is bicolored, with blackish brown to black above and gray or white below (Hall 1981). Darker pelage is more pronounced in southwestern part of range and is more diluted with paler hair or other colors of hair (including red, gray, or brown) to north and east (Anderson 1959). Grayest individuals are generally in northern part of range. Female pelage color varies more than does that of males (Howell 1924)."

From Armstrong et al. (2010): "The montane vole is a medium-sized vole with a tail less than 40 percent of the length of the head and body. The dorsal color is grayish brown to brownish yellow. The venter is silver-gray with white-tipped, black hairs. The tail is indistinctly bicolored."

External measurements

Length measurements are in millimeters (mm) and weight measurements are in grams (g), unless stated otherwise. If available, the sample size (n=) is provided. If a range is not provided and n= is not given, then the listed measurement represents an average.

Part of range Reference Total length Tail length Hindfoot length Ear length Mass
Arizona (White Mountains) Hoffmeister (1986) 124–180 (n=58) 34–48 (n=58) 18.5–22 (n=58)
California Jameson & Peeters (2004) 169–189 39–54 20–27 11–14 30–65
Colorado Armstrong et al. (2010) 140–182 34–62 17–22 11–18 35–60


Variation

This section shows some of the color variation present in Microtus montanus. The location is provided for reference only. The individual shown does not necessarily represent the only color variant within the local population.

  • California, Fresno County
    California, Fresno County
  • Wyoming, Park County
    Wyoming, Park County

Skull

From Armstrong et al. (2010): "The skull is stout with a square braincase. The last upper molar has 5 dentine lakes, the second molar has 4, and the incisive foramina are narrow and constricted posteriorly. The posterior edge of the premaxillaries does not extend beyond the posterior margins of the nasals."

From Naughton (2012): "incisive foramina ≤ 5mm and constrict sharply to points posteriorly; upper incisors of adults protrude beyond the nasal bones when viewed from directly above; M3 has 3 closed triangles and a closed recurved posterior loop; m1 has 4 re-entrant angles on each side."

  • Lateral view of the skull of Microtus montanus.
  • Dorsal view of the skull of Microtus montanus. The upper incisors of adults protrude beyond the nasal bones when viewed from directly above (Naughton, 2012).
  • Ventral view of the skull of Microtus montanus.
  • Upper incisors of Microtus montanus.
  • Lower jaw of Microtus montanus.
  • Upper molars of Microtus montanus.
  • Lower molars of Microtus montanus.
  • Enamel pattern of Microtus montanus. The left pair are the upper molars (top to bottom are M1, M2, M3) and right pair are the lower molars (top to bottom are m1, m2, m3).

Similar species

Comparison with Microtus drummondii

Comparison with Microtus canicaudus

From Sera & Early (2003): "M. montanus is distinguished from allopatric Microtus canicaudus (formerly considered a geographic race of M. montanus-Hall and Kelson 1951) by a distinctive karyotype (Hsu and Johnson 1970; Modi 1986) and different globulin- and hemoglobin-banding patterns (Johnson 1968). In addition, M. canicaudus has a more yellow upper body (Hall 1981)."

Comparison with Microtus longicaudus

From Smolen & Keller (1987): "The relatively long tail in relation to head and body length and hindfoot length separates Microtus longicaudus from most other species of Microtus."

  • Microtus montanus
  • Long-tailed Vole (Microtus longicaudus)
  • Dorsal view of the skull of Microtus montanus. The upper incisors of adults protrude beyond the nasal bones when viewed from directly above (Naughton, 2012).
  • Dorsal view of the skull of Microtus longicaudus. The nasals usually hide the incisors completely when viewed from above (Naughton, 2012).
  • Ventral view of the skull of Microtus montanus. The incisive foramina are narrow and constrict abruptly (Naughton, 2012).
  • Ventral view of the skull of the Long-tailed Vole (Microtus longicaudus). The incisive foramina taper gradually if at all (Naughton, 2012).

Comparison with Microtus mogollonensis

Microtus montanus can be easily confused with M. mogollonensis unless the skull is examined carefully (Armstrong, 2010). From Armstrong et al. (2010): "M. mogollonensis differs from M. montanus in having incisive foramina broad and rounded posteriorly rather than narrow or abruptly constricted posteriorly. The jugal bone of the zygomatic arch is expanded and the posterior margin of the palate is notched or grooved."

  • Ventral view of the skull of the Mogollon Vole (Microtus mogollonensis). The incisive foramina are broad and rounded.
  • Ventral view of the skull of Microtus montanus. The incisive foramina are narrow and constrict abruptly.
  • Lateral view of the skull of the Mogollon Vole (Microtus mogollonensis) showing the jugal bone of the zygomatic arch, which is expanded.
  • Lateral view of the skull of Microtus montanus showing the jugal bone of the zygomatic arch, which is not expanded.

Comparison with Microtus ochrogaster

From Sera & Early (2003): "M. montanus has 3 closed triangles on M3 and 8 mammae, whereas the potentially sympatric M. ochrogaster has only 2 closed triangles on M3 and 6 mammae."

Comparison with Microtus townsendii

From Sera & Early (2003): "Upper body of sympatric M. townsendii has more dark brown or black with a heavier mixture of black-tipped guard hairs than M. montanus, which has a more buffy and grayish wash where these 2 species overlap (Hall 1981)."

Comparison with Phenacomys intermedius

From Armstrong et al. (2010): In Phenacomys intermedius, "the molars of the lower jaw have inner (lingual) reentrant angles that are much deeper than the outer (buccal) reentrant angles, extending more than halfway across the tooth surface. The first lower molar has a variable number (3 to 7) of closed occlusal triangles (McAllister and Hoffman 1988)."

  • Microtus montanus
  • Western Heather Vole (Phenacomys intermedius)
  • Lower molars of Microtus montanus.
  • Lower molars of Phenacomys intermedius. Yellow arrow points to one of the many lingual re-entrant angles of lower cheek teeth, which are disproportionately large (more than halfway through the tooth; Naughton, 2012). The first lower molar (m1) has a variable number of closed triangles (3-7; Naughton, 2014). Black arrows point to the 5 closed triangles on the first lower molar (m1) in this individual.

References

Anderson S. 1959. Distribution, variation, and relationships of the montane vole, Microtus montanus. University of Kansas Publications, Museum of Natural History 9:415-511.

Armstrong DM, Fitzgerald JP, Meaney CA. 2010. Mammals of Colorado, Second Edition. Denver (CO, USA): University Press of Colorado.

Hall ER. 1981. The mammals of North America. Second ed. John Wiley and Sons, New York, 2:601-1181 + 90.

Hall ER, Kelson KR. 1951. A new subspecies of Microtus montanus from Montana and comments on Microtus canicaudus Miller. University of Kansas publications, Museum of Natural History 5: 73-79.

Hoffmeister DF. 1986. Mammals of Arizona. Tucson (AZ, USA): University of Arizona Press.

Howell AB. 1924. Individual and age variation in Microtus montanus yosemite. Journal of Agricultural Research 28:977-1017.

Hsu TC, Johnson ML. 1970. Cytological distinction between Microtus montanus and Microtus canicaudus. Journal of Mammalogy 51:824-826.

Jameson EW, Peeters HJ. 2004. Mammals of California (No. 66). Berkeley (CA, USA): University of California Press.

Johnson ML. 1968. Application of blood protein electrophoretic studies to problems in mammalian taxonomy. Systematic Zoology 17:23-30.

Modi WS. 1986. Karyotypic differentiation among two sibling species pairs of new world microtine rodents. Journal of Mammalogy 67:159-165.

Naughton D. 2012. The natural history of Canadian mammals. Toronto (ON, CA): University of Toronto Press.

Peale TR. 1848. United States Exploring Expedition during the Years 1838, 1839, 1840, 1841, 1842 under the Command of Charles Wilkes, U.S.N. Volume 8, Mammalia and Ornithology. C. Sherman, Philadelphia, 44.

Sera WE, Early CN. 2003. Microtus montanus. Mammalian Species 2003(716): 1-10.

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