Microtus pennsylvanicus
| Eastern Meadow Vole
(Microtus pennsylvanicus) | |
|---|---|
| Range | |
 | |
| Taxonomic classification | |
| Order: | Rodentia |
| Suborder: | Supramyomorpha |
| Infraorder: | Myomorphi |
| Superfamily: | Muroidea |
| Family: | Cricetidae |
| Subfamily: | Arvicolinae |
| Tribe: | Microtini |
| Genus: | Microtus |
| Subgenus: | Pitymys |
| Binomial details | |
| Microtus pennsylvanicus (Ord, 1815) | |
| Other resources | |
| Full taxonomic details at MDD | |
Jackson & Cook (2020) proposed that the eastern clade of Microtus pennsylvanicus now 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 pennsylvanicus. Further studies will be needed to fully understand new species boundaries.
Description
From Best & Hunt (2020): "The meadow vole is a large vole with a bicolored tail that is twice as long as the hind foot. The dorsum varies from yellowish-chestnut to dark chestnut-brown to blackish or grayish with slightly paler sides and a grayish or silvery venter. Pelage is somewhat grayer in winter. Feet and tail are dark on top and paler on the bottom. Ears are round and may be inconspicuous beneath the fur. Meadow voles in the southern parts of their range sometimes are darker."
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 |
|---|---|---|---|---|---|---|
| Carolinas, Virginia, Maryland | Webster et al. (1985) | 139–190 | 39–54 | 34–54 | ||
| Georgia | Woods et al. (1982) | 128–173 (n=14) | 27–43 (n=14) | 18–25 (n=14) | 12–18 (n=7) | 29–75 (n=14) |
| Maryland | Woods et al. (1982) | 146–203 (n=13) | 33–56 (n=13) | 21–25 (n=13) | 13–16 (n=13) | 37–62 (n=13) |
| Nebraska | Johnsgard (2020) | 140–190 | 32–52 | 30–75 |
Skull
From Naughton (2012): "(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 (arrows) 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."
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Lateral view of the skull of Microtus pennsylvanicus -
Dorsal view of the skull of Microtus pennsylvanicus -
Ventral view of the skull of Microtus pennsylvanicus -
Dorsal view of the lower jaw of Microtus pennsylvanicus -
Skull of Microtus pennsylvanicus showing the upper incisors, which lack grooves. Note: one of the upper incisors is chipped. -
Upper molars of Microtus pennsylvanicus.The second upper molar (M2) has 5 closed loops (black arrows; 3 triangles and an anterior loop plus a usually rounded, closed lingual posterior loop which may resemble an incipient 5th triangle in some individuals (Naughton, 2012). Naughton (2012) also notes that "M3 usually has 3 re-entrant angles (yellow arrows) on either side but this trait is variable especially on the labial side, where a 4th incipient angle may occur." -
Lower molars of Microtus pennsylvanicus. From Naughton (2012): "m1 has 4 and sometimes 5 lingual and 4 labial re-entrant angles". Yellow arrows point to the re-entrant angles in the first lower molar (m1) on the right side of the lower jaw.
Similar species
Comparison with Microtus chrotorrhinus and M. pinetorum
The Rock Vole (Microtus chrotorrhinus) and the Woodland Vole (Microtus pinetorum) are easily recognized by their unique habitats (deciduous forests and rocky areas, respectively) and by the short tail length of M. pinetorum and the yellow rostrum of M. chrotorrhinus (Everson et al., 2023).
Comparison with Microtus drummondii
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.
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Microtus pennsylvanicus. -
Western Meadow Vole (Microtus drummondii). -
Range of Microtus pennsylvanicus based on Jackson & Cook (2020). -
Range of Microtus drummondii based on Jackson & Cook (2020).
Comparison with Microtus ochrogaster
From Everson et al. (2023): "Microtus ochrogaster and M. pennsylvanicus, on the other hand, often occupy the same habitats and are exceptionally difficult to distinguish based on external characteristics (Adams et al. 2017). While mammalogists often rely on external measurements and pelage coloration to distinguish between species, our results suggest that these characteristics do not reliably distinguish the vole species M. ochrogaster and M. pennsylvanicus in our study region [Kentucky] where they occur in sympatry. Despite statistical differences between six external traits, too much measurement range overlap occurred for reliable field identification. Ventral fur coloration was also not a reliable field trait for distinguishing these two species in our study region. While M. ochrogaster is described as having yellow or buffy ventral fur and M. pennsylvanicus as having gray or silvery ventral fur, we found most individuals in Kentucky to have intermediate buffy-gray coloration. Thus, while ventral fur color might be a useful character in other parts of the their ranges, it cannot effectively be used to identify the two species where they co-occur in Kentucky. Our results align with previous studies that demonstrated limited utility of these external morphological characteristics in distinguishing the two species (DeCoursey 1957; Henterly et al. 2011). However, we acknowledge that this study did not consider mammae count, another external trait often used in species identification; M. ochrogaster is known to have six mammae, whereas M. pennsylvanicus has eight. This character may well be useful for species identification in our study region. [Additionally] our results suggest that molar cusp pattern is the most accurate morphological character used to distinguish M. ochrogaster and M. pennsylvanicus. We found that 94% of individuals that were assigned to species based on dentition were also recovered within their respective mitochondrial clade."
Best & Hunt (2020) provides: "They [Microtus pennsylvanicus] are difficult to distinguish from other members of the genus except by characteristics of their teeth. Prairie voles [Microtus ochrogaster] have relatively shorter tails, and they have cusps on the third upper molar that form two closed triangles between the anterior and posterior loops, while meadow voles [Microtus pennsylvanicus] have three such triangles."
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Microtus pennsylvanicus. -
Prairie Vole (Microtus ochrogaster).
Molecular identification
Form Henterley et al. (2011): For differentiation of Microtus ochrogaster and Microtus pennsylvanicus: "Genomic DNA was extracted using DNeasy kits (Qiagen, Valencia,CA) and the avpr1a genotypes of voles were determined by polymerase chain reaction (PCR), with primers specifically designed to amplify the microsatellite region of the avpr1a gene in prairie voles (Hammock and Young, 2005). Our avpr1a genotyping procedure was identical to that followed by Solomon et al. (2009), who confirmed that these primers amplified the targeted region of the avpr1a gene by sequencing the resulting PCR product and comparing the sequence to the prairie vole avpr1a gene sequence published in GenBank. Previous studies using the same primers as in our investigation have demonstrated that PCR amplification of this microsatellite region of the avpr1a gene in known Microtus pennsylvanicus yields PCR fragments that are 200–300 bp, while in known M. ochrogaster the resultant PCR fragments are 600–800 bp (Young et al., 1999; Fink et al., 2006).
References
Adams NE, Inoue K, Solomon NG. 2017. Range-wide microsatellite analysis of the genetic population structure of prairie voles (Microtus ochrogaster). The American Midland Naturalist 177(2):183-199.
Best TL, Hunt JL. 2020. Mammals of the southeastern United States. Tuscaloosa (AL, USA): University Alabama Press.
DeCoursey Jr GE. 1957. Identification, ecology and reproduction of Microtus in Ohio. Journal of Mammalogy 38(1):44-52.
Everson KM, McGinnis RC, Burdine OP, Huddleston TR, Hylick TM, Keith AL, Moore SC, O’Brien AE, Vilardo AL, Krupa JJ. 2023. Disentangling morphology and genetics in two voles (Microtus pennsylvanicus and M. ochrogaster) in a region of sympatry. Journal of Mammalogy 104(3):532-545.
Fink S, Excoffier L, Heckel G. 2006. Mammalian monogamy is not controlled by a single gene. Proceedings of the National Academy of Sciences 103(29):10956-10960.
Hammock EA, Young LJ. 2005. Microsatellite instability generates diversity in brain and sociobehavioral traits. Science 308(5728):1630-1634.
Henterly AC, Mabry KE, Solomon NG, Chesh AS, Keane B. 2011. Comparison of morphological versus molecular characters for discriminating between sympatric meadow and prairie voles. The American Midland Naturalist 165(2):412-420.
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.
Ord G. 1815. Zoology. Pp. 290–361 in Guthrie, W. (eds.). A new geographical, historical, and commercial grammar; and present state of the several kingdoms of the world. In two volumes. Vol. II. Johnson & Warner, Philadelphia, 603 pp.
Solomon NG, Richmond AR, Harding PA, Fries A, Jacquemin S, Schaefer RL, Lucia KE, Keane B. 2009. Polymorphism at the avprla locus in male prairie voles correlated with genetic but not social monogamy in field populations. MoI. Eroi, 18:4680-4695.
Webster WD, Parnell JF, Biggs WC. 1985. Mammals of the Carolinas, Virginia, and Maryland. Chapel Hill (NC, USA): University of North Carolina Press.
Woods CA, Post W, Kilpatrick CW. 1982. Microtus pennsylvanicus (Rodentia: Muridae) in Florida: a Pleistocene relict in a coastal saltmarsh. Bulletin of the Florida Museum of Natural History. Biological Sciences 28(2):25-52.
Young LJ, Nilsen R, Waymire KG, Macgregor GR, Insel TR. 1999. Increased affiliative response to vasopressin in mice expressing the Vhl receptor from monogamous vole. Nature 400:766-768.