Sorex cinereus
Masked Shrew
(Sorex cinereus) | |
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Range | |
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Taxonomic classification | |
Order: | Eulipotyphla |
Suborder: | Erinaceota |
Family: | Soricidae |
Subfamily: | Soricinae |
Tribe: | Soricini |
Genus: | Sorex |
Subgenus: | Otisorex |
Species group: | Sorex cinereus group |
Binomial details | |
Sorex cinereus Kerr, 1792 |
From Woodman (2018): "Molecular analyses of the Sorex cinereus group (Demboski and Cook, 2003; Hope et al., 2012) have provided intriguing insight into relationships among species and populations, including low genetic divergence among a number of recognized arctic species and the presence of unrecognized cryptic species. As currently understood, S. cinereus is almost certainly paraphyletic (Stewart et al., 1993; Hope et al., 2012). Unfortunately, sampling for genetic studies remains insufficient to completely elucidate the relationships of genetic clades to named subspecies, the geographic distributions of clades, or the taxonomy of the S. cinereus group. "
Description
Sorex cinereus is the most widespread shrew in North America. It is a small, brown to dark grayish-brown, long-tailed shrew. The ventral coloration ranges from gray to buffy-gray. The dorsal and ventral coloration varies across the range of the species with some individuals appearing indistinctly tricolored, yellowish, or reddish. The tail is dark above and lighter below, but not strongly bicolored. Often, the tail has a dark tip that is more visible from below. Winter coloration tends to be darker than summer coloration. The snout is long and pointed. Characteristic of the genus, the tips of teeth are chestnut (due to iron deposits), including the inner ridges of the upper unicuspids. Subadults and juveniles typically have thicker tails than older adults. This species can be difficult to tell apart from other brown Sorex species within its range. External measurements will differentiate S. cinereus from some similar-looking species. However, in some cases, careful examination of the upper incisors, unicuspids, and length of the skull may be required in order to be confident of the species.
From Best & Hunt (2020) for the southeastern US: "This is a small shrew with a relatively long tail and a long, pointed snout. Eyes and ears are small but visible. The dorsum is brown, the ventrum is a paler silvery-tan, and the pelage is somewhat paler in summer."
From Armstrong et al. (2010) for Colorado: "The masked shrew is medium grayish to brownish in color, slightly paler on the ventral surface. The tail is indistinctly bicolored. Pelage is slightly paler in winter than in summer."
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 |
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Alaska and British Columbia (subspecies streatori) | Woodman and Fisher (2016) | 90–122 (n=105) | 32–53 (n=105) | 10–16 (n=105) | ||
British Columbia (southwestern) | Nagorsen and Panter (2009) | 93–119 (n=34) | 40–49 (n=36) | 10–13 (n=37) | 3.2–4.7 (n=5) | |
Canada | Naughton (2012) | 75–125 | 28–50 | 8–14 | 6–10 | 2.2–8.0 |
Carolinas, Virginia, Maryland | Webster et al. (1985) | 88–104 | 31–40 | 10–13 | ||
Colorado | Armstrong et al. (2010) | 80–109 | 35–46 | 11–12 | 3–6 | |
Great Lakes Region | Kurta (2017) | 75–100 | 31–45 | 10–13 | 3.5–5.5 | |
Minnesota | Hazard (1982) | 83–104 | 36–41 | 11–12 | 4–8 | 3.0–6.5 |
New York | Kirkland Jr. (1977) | 97.17 (n=24) | 39.54 (n=24) | 11.29 (n=24) | ||
North Dakota | Seabloom et al. (2020) | 94.5 | 40 | 11 | 6 | |
Pennsylvania | Kirkland Jr. (1977) | 94.04 (n=26) | 36.21 (n=26) | 11.62 (n=26) | ||
rangewide | Wilson & Ruff (editors, 1999) | 75–125 | 28–50 | 2.2–5.4 | ||
Virginia | Linzey (1998) | 85–100 | 30–40 | 3–7 | ||
Washington and British Columbia (subspecies cinereus) | Woodman and Fisher (2016) | 88–118 (n=55) | 35–49 (n=55) | 11–14 (n=55) |
Color variation
From van Zyll de Jong (1983): "Colour in species as a whole rather variable, yellowish and reddish-brown individuals occasionally occur, and some areas there is a tendency to a tricolour pattern."
Geographic variation
This section shows some of the color variation present in Sorex cinereus. The location is provided for reference only. The individual shown does not necessarily represent the only color variant within the local population.
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Alaska, Denali Borough
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Alaska, Southeast Fairbanks Census Area, subadult
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Colorado, Boulder County
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Massachusetts, Worcester County
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Virginia, Giles County
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Virginia, Giles County
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Wisconsin, Lincoln County
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Wisconsin, Lincoln County
Skull characters
Sorex cinereus skull characters | |
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units in mm | |
Skull | |
Condylobasal length: | 14.3–16.1 (French, 1980); 14.6–16.9 (Álvarez-Castañeda, 2024) |
Postmandibular canal: | Absent |
Shape: | Rounded braincase |
Dental | |
Upper unicuspids: | 5 |
Unicuspid notes: | U3≥U4; U1–U4 are in an almost graduated series |
Tines present: | Yes |
Tine size: | Medium |
Tine position: | Well below upper limit of pigment on upper incisors |
Shape upper incisors: | Parallel or slightly diverging |
Dental characters: | Tips of upper incisors are more widely separated partly because of tines |
Nagorsen and Panter (2009) provide the following diagnostic qualitative traits for identifying Sorex cinereus: "There are 6 paired toe pads on the 3rd 4th digits of the hind foot. The third unicuspid is equal or slightly longer than the fourth unicuspid. The medial edges of the upper incisors are straight. The medial tines on the upper incisors are large and positioned well below the upper edge of pigment."
From Armstrong et al. (2010): "Greatest length of skull is 14–16 mm. The third unicuspid is as large as or larger than the fourth."
Similar species
Alaska
In Alaska, Sorex cinereus is similar in appearance and may be confused with the Barren Ground Shrew (Sorex ugyunak). Externally, Sorex ugyunak can be differentiated from S. cinereus by its tricolored pelage and length of the tail. The skulls of S. ugyunak and S. cinereus are similar. However, in S. ugyunak the anterior position of the infraorbital and lacrimal formina help distinguish this species from S. cinereus (Van Zyll de Jong, 1991).
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Barren Ground Shrew (Sorex ugyunak). -
Sorex cinereus from Denali Borough, Alaska.
Contiguous United States
From Whitaker (2004): "Sorex cinereus is most similar to S. fontinalis, S. haydeni, and S. longirostris. S. cinereus is distinguished from S. longirostris by having a longer thicker tail, a longer thinner rostrum (ratio of greatest rostral width, the width measured across the rostrum from outside 1st large molariform teeth with the length measured as the distance from posterior end of palate to anterior end of I1 is < 2.0), and pigmentation of inner ridges of upper unicuspids. Unicuspids 3 and 4 are usually subequal in size in S. cinereus, whereas the 3rd unicuspid is usually smaller than the 4th in S. longirostris, and the 4th unicuspid is often, but not always, larger than the 3rd in S. fontinalis. S. cinereus is distinguished from S. haydeni by its darker brownish color and longer tail with more tuft."
From Best & Hunt (2020): "Cinereus shrews are distinguished from southeastern shrews [Sorex longirostris] by having a longer and thicker tail, a longer and thinner snout, and pigmentation on the inner ridges of upper unicuspids. Cinereus shrews are smaller and paler than smoky shrews [Sorex fumeus], and cinereus shrews have a much longer tail than North American least shrews [Cryptotis parvus].
For Colorado, from Armstrong et al. (2010): "This species is difficult to distinguish from the montane shrew [Sorex monticolus] without careful examination of the teeth." In S. monticolus, the third unicuspid is smaller than the fourth; whereas in S. cinereus the third unicuspid is slightly larger to equal in size to the fourth unicuspid.
From van Zyll de Jong (1983), comparing S. cinereus with S. haydeni: "Sorex haydeni, ventral coloration of tail with pale terminal tuft (brownish rather than blackish), length of upper unicuspid row usually <2.20 and unicuspids usually wider than long (for doubtful cases see van Zyll de Jong 1980)."
If only the skull is available, S. cinereus can be differentiated from S. fumeus by the length of the skull (>17 mm in S. fumeus and <17 in S. cinereus; van Zyll de Jong, 1983) and the shape of the upper incisors (curved in S. fumeus and straight in S. cinereus). S. cinereus can be separated from S. dispar by the location of the posterior border of the infraorbital foramen relative to the space between the first and second upper molars (space between M1 and M2; van Zyll de Jong, 1983; Naughton, 2012; Diersing, 2019). Comparison of the skulls of Sorex cinereus, S. fumeus and S. dispar below.
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The anterior margin of the zygomatic plate in Sorex cinereus is located over posterior end of the first molar (M1). Based on Diersing (2019). -
The anterior margin of the zygomatic plate in Sorex fumeus is located over posterior end of the first molar (M1). Based on Naughton (2012). -
In S. dispar, the anterior margin of the zygomatic plate is located over the anterior end of the second molar (M2). Based on Naughton (2012) and Diersing (2019).
References
Álvarez-Castañeda ST. 2024. Order Eulipotyphla. In Mammals of North America-Volume 1: Systematics and Taxonomy (pp. 397-513). Cham (Switzerland): Springer Nature Switzerland.
Armstrong DM, Fitzgerald JP, Meaney CA. 2010. Mammals of Colorado, Second Edition. Denver (CO, USA): University Press of Colorado.
Best TL, Hunt JL. 2020. Mammals of the southeastern United States. Tuscaloosa (AL, USA): University Alabama Press.
Demboski JR, Cook JA. 2003. Phylogenetic diversification within the Sorex cinereus group (Soricidae). Journal of Mammalogy 84(1): 144-158.
Diersing VE. 2019. Taxonomic revision of the long-tailed shrew, Sorex dispar Batchelder, 1911, from the Appalachian Region of North America, with the description of a new subspecies. Journal of Mammalogy 100(6): 1837-1846.
Hazard EB. 1982. The mammals of Minnesota. Minneapolis (MN, USA): University of Minnesota Press.
Hope AG, Speer KA, Demboski JR, Talbot SL, Cook JA. 2012. A climate for speciation: rapid spatial diversification within the Sorex cinereus complex of shrews. Molecular Phylogenetics and Evolution 64(3): 671-684.
Kerr R. 1792. The Animal Kingdom, or Zoological System of the celebrated Sir Charles Linnaeus. Class I. Mammalia. A. Strahan, T. Cadell, and W. Creech, Edinburgh, 462 pp.
Kirkland Jr GL. 1977. A re-examination of the subspecific status of the Maryland shrew, Sorex cinereus fontinalis Hollister. In Proceedings of the Pennsylvania Academy of Science (pp. 43-46). Pennsylvania Academy of Science.
Kurta A. 2017. Mammals of the Great Lakes region. Ann Arbor (MI, USA): University of Michigan Press.
Linzey DW. 1998. The mammals of Virginia. McDonald & Woodward Publishing.
Nagorsen DW, Panter N. 2009. Identification and status of the Olympic shrew (Sorex rohweri) in British Columbia. Northwestern Naturalist 90(2): 117-129.
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.
Stewart DT, Baker AJ, Hindocha SP. 1993. Genetic differentiation and population structure in Sorex haydeni and S. cinereus. Journal of Mammalogy 74(1): pp.21-32.
van Zyll de Jong CG, 1980. Systematic relationships of woodland and prairie forms of the common shrew, Sorex cinereus cinereus Kerr and S. c. haydeni Baird, in the Canadian Prairie Provinces. Journal of Mammalogy 61(1): 66-75.
van Zyll de Jong CG. 1983. Handbook of Canadian Mammals. Volume 1: Marsupials and Insectivores. Ottawa (ON, Canada): National Museums of Canada.
van Zyll de Jong CG. 1991. Speciation of the Sorex cinereus group. Pp. 65-73 in The biology of the Soricidae (J. S. Findley and T. L. Yates, eds.). Special Publication, Museum of Southwestern Biology 1:1-91.
Webster WD, Parnell JF, Biggs WC. 1985. Mammals of the Carolinas, Virginia, and Maryland. Chapel Hill (NC, USA): University of North Carolina Press.
Whitaker JO. 2004. Sorex cinereus. Mammalian Species (743): 1-9.
Wilson DE, Ruff S, editors. 1999. The Smithsonian Book of North American Mammals. Washington D.C. (USA): Smithsonian Institution Scholarly Press.
Woodman N. 2018. American Recent Eulipotyphla: nesophontids, solenodons, moles, and shrews in the New World. Washington D.C. (USA): Smithsonian Institution Scholarly Press. https://doi.org/10.5479/si.1943-6696.650.
Woodman N, Fisher RD. 2016. Identification and distribution of the Olympic Shrew (Eulipotyphla: Soricidae), Sorex rohweri Rausch et al., 2007 in Oregon and Washington, based on USNM specimens. Proceedings of the Biological Society of Washington 129(1): 84-102.