Microtus drummondii

Western Meadow Vole
(*Microtus drummondii*)
Western Meadow Vole (Microtus drummondii)
Range
Taxonomic classification
Order:	Rodentia
Suborder:	Supramyomorpha
Infraorder:	Myomorphi
Superfamily:	Muroidea
Family:	Cricetidae
Subfamily:	Arvicolinae
Tribe:	Arvicolini
Genus:	Microtus
Subgenus:	Mynomes
Binomial details
	Microtus drummondii (Audubon & Bachman, 1854)
Other resources
	Full taxonomic details at MDD

The Western Meadow Vole (Microtus drummondii) is fairly large vole. The species is widely distributed in the western United States and most commonly found in grasslands, preferring moister areas, but may also be found in woodlands (Burt and Grossenheider, 1976). This species was recently split from Microtus pennsylvanicus by Jackson & Cook (2020).

Description

The following description is from Armstrong et al. (2010), describing Microtus pennsylvanicus in Colorado, before the species was split by Jackson & Cook (2020): "This is a fairly large, dark-colored vole with a gray to silvery belly. Dorsal color is usually dark gray-brown to chestnut. The tail is bicolored and scantily haired. The tail is longer than that of most prairie voles [Microtus ochrogaster] but relatively shorter than in the long-tailed vole [Microtus longicaudus]. The ears are rounded and inconspicuous beneath the long fur on the head. Younger animals are typically darker in color than are older individuals."

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
Colorado	Armstrong et al. (2010)	155–192	35–67	20–24	11–18	35–75
Minnesota	Hazard (1982)	137–171	32–43	17–20	10–15	31.3–52.2
North Dakota	Seabloom et al. (2020)	155	39	19	12	40

Color variation

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

Adult, Denali Borough, Alaska
Adult, Morton County, North Dakota
Adult, Stutsman County, North Dakota
Adult, Stutsman County, North Dakota
Juvenile, Stutsman County, North Dakota
Subadult, Lincoln County, Wisconsin
Adult, Park County, Wyoming

Skull

The following characters identified by Naughton (2012) are for M. pennsylvanicus, before the species was split by Jackson & Cook (2020): "(a) M2 has 5 closed loops (3 triangles and an anterior loop plus a rounded, closed lingual posterior loop which may resemble an incipient 5th triangle in some individuals); (b) M3 usually has 3 re-entrant angles on either side but this trait is variable especially on the labial side, where a 4th incipient angle may occur; c) triangles on m1 are narrow and usually sharply pointed, especially on lingual side; d) m1 has 4 and sometimes 5 lingual and 4 labial re-entrant angles."

NEON06JK0. Microtus drummondii. Stutsman County, North Dakota. Dorsal view of the skull.
NEON06JK0. Microtus drummondii. Stutsman County, North Dakota. Lateral view of the skull.
NEON06JK0. Microtus drummondii. Stutsman County, North Dakota. Ventral view of the skull.
NEON06JK0. Microtus drummondii. Stutsman County, North Dakota. Dorsal view of the mandible.
NEON06JK0. Microtus drummondii. Stutsman County, North Dakota. Upper incisors.
NEON06JK0. Microtus drummondii. Upper molars. Black arrows point to the three closed triangles on the second upper molar (M2). The purple arrow points to the usually rounded, closed lingual posterior loop on the M2, which is found only in Microtus drummondii and Microtus pennsylvanicus.
NEON01IO2. Microtus drummondii. Stutsman County, North Dakota. Enamel pattern.. 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).
Enamel pattern of the upper molars in Microtus drummondii. Arrows point to a rounded, closed lingual posterior loop on the second upper molar (M2), which may resemble an incipient 5th triangle in some individuals. This anterior loop is only found in Microtus drummondii and the Eastern Meadow Vole (Microtus pennsylvanicus).

Similar species

Comparison with Clethrionomys

The Southern Red-backed Vole (Clethrionomys gapperi) and the Northern Red-backed Vole (Clethrionomys rutilus) are easily distinguished from Microtus drummondii by the broad, reddish mid-dorsal stripe extending from forehead to tail.

Dorsal view of the Southern Red-backed Vole (Clethrionomys gapperi) showing the broad, reddish mid-dorsal stripe extending from forehead to tail.
Dorsal view of Northern Red-backed Vole (Clethrionomys rutilus) showing the broad, reddish mid-dorsal stripe extending from forehead to tail.
Dorsal view of the Western Meadow Vole (Microtus drummondii)

Comparison with Microtus abbreviatus

In the field, the Singing Vole (Microtus abbreviatus) can be distinguished from Microtus drummondii by its much shorter tail.

Western Meadow Vole (Microtus drummondii)
Singing Vole (Microtus abbreviatus)
NEON06JK0. Dorsal view of the skull of the Western Meadow Vole (Microtus drummondii).
UAM:Mamm:64379. Dorsal view of the skull of the Singing Vole (Microtus abbreviatus).
NEON06JK0. Microtus drummondii. Upper molars. Black arrows point to the three closed triangles on the second upper molar (M2). The purple arrow points to the usually rounded, closed lingual posterior loop on the M2, which is found only in Microtus drummondii and Microtus pennsylvanicus.

Comparison with Microtus longicaudus

In the field, the Long-tailed Vole (Microtus longicaudus) can be distinguished from Microtus drummondii by its much longer tail. The tail of M. longicaudus is greater than one-third the length of the head and body.

Western Meadow Vole (Microtus drummondii)
Long-tailed Vole (Microtus longicaudus)
NEON06JK0. Microtus drummondii. Upper molars. Black arrows point to the three closed triangles on the second upper molar (M2). The purple arrow points to the usually rounded, closed lingual posterior loop on the M2, which is found only in Microtus drummondii and Microtus pennsylvanicus.

Comparison with Microtus montanus

Western Meadow Vole (Microtus drummondii)
Montane Vole (Microtus montanus)
NEON06JK0. Microtus drummondii. Upper molars. Black arrows point to the three closed triangles on the second upper molar (M2). Each purple arrow points to the usually rounded, closed lingual posterior loop on each M2, which is found only in Microtus drummondii and Microtus pennsylvanicus.
NEON01IA2. Upper molars of Montane Vole (Microtus montanus).

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."

Western Meadow Vole (Microtus drummondii)
Prairie Vole (Microtus ochrogaster)
NEON06JK0. Microtus drummondii. Upper molars. Black arrows point to the three closed triangles on the second upper molar (M2). The purple arrow points to the usually rounded, closed lingual posterior loop on the M2, which is found only in Microtus drummondii and Microtus pennsylvanicus.

Comparison with Microtus pennsylvanicus

Jackson & Cook (2020) proposed that the eastern clade of Microtus pennsylvanicus be referred to as Microtus pennsylvanicus (Ord 1815) and the western clade as Microtus drummondii (Audubon and Bachman 1853). The ranges published by Jackson & Cook (2020) represent hypothesized range limits of each clade based on a cytochrome b (Cytb) analysis. Further studies will be needed to fully understand new species boundaries. In areas where these two species may co-occur, it may not currently be possible to distinguish them using morphological characters.

Western Meadow Vole (Microtus drummondii)
Eastern Meadow Vole (Microtus pennsylvanicus)
Range of the Western Meadow Vole (Microtus drummondii) based on Jackson & Cook (2020).
Range of Microtus pennsylvanicus based on Jackson & Cook (2020).

Comparison with Microtus richardsoni

In the field, North American Water Vole (Microtus richardsoni) can be distinguished from Microtus drummondii by its much larger size. Additionally, the fur on the underparts of M. richardsoni is plumbeous, with white or silvery-white wash, instead of pale buff, grey, or silvery in M. drummondii.

Western Meadow Vole (Microtus drummondii)
Ventral view of the Western Meadow Vole (Microtus drummondii). The color of the underparts ranges from pale buff to grey or silvery.
North American Water Vole (Microtus richardsoni). Note the size of the scale bar. This is the largest vole in North America.
Ventral view of the North American Water Vole (Microtus richardsoni). The underparts are plumbeous with white or silvery-white wash.
NEON06JK0. Microtus drummondii. Upper molars. Black arrows point to the three closed triangles on the second upper molar (M2). The purple arrow points to the usually rounded, closed lingual posterior loop on the M2, which is found only in Microtus drummondii and Microtus pennsylvanicus.

Comparison with Phenacomys intermedius

Western Meadow Vole (Microtus drummondii)
Western Heather Vole (Phenacomys intermedius)

Taxonomy

Jackson & Cook (2020) proposed that the eastern clade of Microtus pennsylvanicus be referred to as Microtus pennsylvanicus (Ord 1815), the western clade as Microtus drummondii (Audubon and Bachman 1853), and the coastal Florida clade as Microtus dukecampbelli (Woods, Post, and Kilpatrick 1982). The work by Jackson & Cook (2020) is based on a cytochrome b (Cytb) analysis and the range map to the right represents the hypothesized range limit of Microtus drummondii. Further studies will be needed to fully understand new species boundaries.

References

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

Burt WH, Grossenheider RP. 1976. A field guide to the mammals. Boston (MA, USA): Houghton Mifflin.

Hazard EB. 1982. The mammals of Minnesota. Minneapolis (MN, USA): University of Minnesota Press.

Jackson DJ, Cook JA. 2020. A precarious future for distinctive peripheral populations of meadow voles (Microtus pennsylvanicus). Journal of Mammalogy 101(1):36-51.

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

Seabloom R, Hoganson JW, Jensen WF. 2020. The mammals of North Dakota. Fargo (ND, USA): North Dakota State University Press.