Sorex merriami
| Merriam's Shrew
(Sorex merriami) | |
|---|---|
| Range | |
 | |
| Taxonomic classification | |
| Order: | Eulipotyphla |
| Suborder: | Erinaceota |
| Family: | Soricidae |
| Subfamily: | Soricinae |
| Tribe: | Soricini |
| Genus: | Sorex |
| Subgenus: | Incertae sedis |
| Species group: | Sorex merriami group |
| Binomial details | |
| Sorex merriami Dobson, 1890 | |
| Other resources | |
| Full taxonomic details at MDD | |
Description
From Johnson and Clanton (1954) for Washington: "There is a clear cut summer and winter pelage. Without going into a more formal description, these may be noted as follows: Summer: pale grizzled brown dorsally, very light ventrally, white washed with buff. Winter: pale brownish gray dorsally, nearly pure white ventrally. The hair is noticably longer in summer. In both pelages the under fur is darker both dorsally and ventrally. The tail is distinctly bicolor winter and summer, pale brown above and white below. Feet are white winter and summer."
From Armstrong and Jones (1971): "color in summer grayish drab above, becoming paler on flanks, underparts nearly white, faintly tinged with buff; winter pelage brighter, drab above, paler below; tail markedly bicolored, sparsely haired and drab above, white below"
From Verts & Carraway (1998) for Oregon: "S. merriami is medium dark-brown on the dorsum, pinkish white on the venter; the tail is sharply bicolored in the same tones as the body with dark and light portions about equal."
From Jameson and Peeters (2004) for California: "A small species with a conspicuously bicolored tail. The dorsum is gray brown, and the underparts and feet are white."
From Armstrong et al. (2010) for Colorado: "Merriam's shrew is medium-sized and grayish in color with whitish feet and underparts. The tail is conspicuously bicolored and sparsely haired."
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 | Diersing and Hoffmeister (1977) | 89–101 (n=11) | 33–42 (n=11) | 11–13 (n=11) | ||
| Arizona (Coconino Co.) | Hoffmeister (1986) | 89–101 (n=11) | 33–42 (n=11) | 11–13 (n=11) | ||
| California | Jameson & Peeters (2004) | 99–107 | 33–42 | 11–13 | 8–9 | 4.4–6.5 |
| California (north), Oregon, Nevada (north) | Diersing and Hoffmeister (1977) | 88–89 (n=5) | 32–35 (n=5) | 11–12 (n=5) | ||
| California (southeast) and Nevada (southwest) | Diersing and Hoffmeister (1977) | 97–104 (n=3) | 36–41 (n=3) | 11.2–12 (n=3) | ||
| Colorado | Armstrong et al. (2010) | 88–107 | 33–42 | 11–13 | 4–7 | |
| Colorado (north-central), Nebraska (west), Wyoming (southeast) | Diersing and Hoffmeister (1977) | 90–99 (n=6) | 32–39 (n=6) | 11–13 (n=6) | ||
| Colorado (south) and New Mexico (north) | Diersing and Hoffmeister (1977) | 85–104 (n=8) | 33–42 (n=8) | 11–13 (n=8) | ||
| Idaho | Diersing and Hoffmeister (1977) | 87–96 (n=3) | 31–35 (n=3) | 11.3–12 (n=3) | ||
| Montana, Wyoming (north) | Diersing and Hoffmeister (1977) | 96–101 (n=6) | 33–39 (n=6) | 11–13 (n=6) | ||
| North Dakota | Seabloom et al. (2020) | 96 | 36 | 12 | 5 | |
| not reported | Shaughnessy and Woodman (2015) | head and body: 49–77 (n=9) | 32–42 (n=9) | 11–13 (n=9) | ||
| Oregon | Verts & Carraway (1998) | 82–94 | 30–37 | 11–12 | 2.4–4.3 | |
| rangewide | Naughton (2012) | 88–107 | 30–43 | 11–14 | 8–9 | 4.4–6.5 |
| rangewide | Wilson & Ruff (editors, 1999) | 88–107 | 33–42 | 4–7 | ||
| Utah (south) | Diersing and Hoffmeister (1977) | 94–107 (n=7) | 35–41 (n=7) | 12–14 (n=7) | ||
| Washington | Diersing and Hoffmeister (1977) | 84–98 (n=53) | 30–42.5 (n=53) | 11–14 (n=53) |
Skull
| Sorex merriami skull characters | |
|---|---|
| units in mm | |
| Skull | |
| Condylobasal length: | 15.7–17.1 (Armstrong & Jones, 1971), 16–18 (Armstrong, 2010); 15.1–16.9 (Álvarez-Castañeda, 2024) |
| Postmandibular canal: | Present |
| Shape: | Braincase relatively flat |
| Dental | |
| Upper unicuspids: | 5 |
| Unicuspid notes: | U3>U4; U2 is largest |
| Tines present: | No |
| Shape upper incisors: | Converging |
| Dental characters: | Tips of upper incisors are close together since teeth converge distally |
Species diagnosis from Diersing & Hoffmeister (1977): "Postmandibular foramen always present, unicuspid 3 larger than unicuspid 4 (or in a few cases, same size) upper unicuspids without pigmented ridge from apices to cingulum; rostrum broad (best illustrated by measurement across second upper unicuspids, which is usually more than 2.0 mm); I1 lacking tines on medial side; upper M3 situated more medially to toothrow so that breadth across M3 relative to greatest breadth of toothrows is narrow; upper unicuspid toothrow short."
From Hoffmeister (1986): "with the subgeneric characters of a post-mandibular foramen, without a pigmented ridge on upper unicuspids, third upper unicuspid larger than fourth; and tines absent on medial side of first upper incisors; upper M3 situated medial to toothrow so that breadth across M3's narrow; broad rostrum."
From Armstrong et al. (2010): "Greatest length of skull is 16–18 mm. The skull has a short, broad rostrum, abruptly truncated anteriorly, with the braincase flattened and not much higher than the rostrum. The dentition is stout, with the second unicuspid the largest and the third unicuspid larger than the fourth."
From Jameson & Peeters (2004): "Inner side of lower jaw with postmandibular canal; inner (median) surface of unicuspid teeth without pigmented ridge; third upper unicuspid larger than fourth; upper incisor lacking median tine (or minute lobe) when viewed anteriorly."
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Dorsal view of the skull of Sorex merriami. -
Ventral view of the skull of Sorex merriami. -
Lateral view of the skull of Sorex merriami from southwestern Colorado. Long scale bar is 1 cm. -
Lateral view of the skull of Sorex merriami from northwestern Colorado. This is an old individual with worn teeth. Long scale bar is 1 cm. -
Upper incisors of Sorex merriami. Borrowed from Diersing & Hoffmeister (1977). -
Upper incisors of Sorex merriami. -
Unicuspids of Sorex merriami, modified from Diersing & Hoffmeister (1977).
Similar species
Comparison with Sorex arizonae
From Hoffmeister (1986) for Arizona: "Sorex merriami in size and color is most similar to S. arizonae, but merriami has no tines on the medial side of the first upper incisors."
Upper incisors of Sorex merriami. Borrowed from Diersing & Hoffmeister (1977). -
Upper incisors of Arizona Shrew (Sorex arizonae). Borrowed from Diersing & Hoffmeister (1977).
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Unicuspids of Sorex merriami. Modified from Diersing & Hoffmeister (1977). Unisucpid 3 is larger than unicuspid 4. -
Unicuspids of Arizona Shrew (Sorex arizonae). Borrowed from Diersing & Hoffmeister (1977). Unisucpid 3 is equal to or slightly larger than unicuspid 4.
Comparison with all other shrews
Sorex merriami can be distinguished from all other Sorex species in the US by the lack of tines on the upper incisors and only the tips of upper incisors being close together since the teeth converge distally. Sorex sonomae also lack tines on the upper incisors but the medial edge of the upper incisors are parallel.
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Upper incisors of Sorex merriami. Borrowed from Diersing & Hoffmeister (1977). -
Upper incisors of Sorex sonomae. Scale is 1 mm.
References
Armstrong DM, Fitzgerald JP, Meaney CA. 2010. Mammals of Colorado, Second Edition. Denver (CO, USA): University Press of Colorado.
Armstrong DM, Jones JK. 1971. Sorex merriami. Mammalian Species (2): 1-2.
Diersing VE, Hoffmeister DF. 1977. Revision of the shrews Sorex merriami and a description of a new species of the subgenus Sorex. Journal of Mammalogy 58(3): 321-333.
Dobson GE. 1890. Monograph of the Insectivora, Systematic and Anatomical. Part 3, fasc. 1, pl. 23, fig. 6 and explanation.
Hoffmeister DF. 1986. Mammals of Arizona. Tucson (AZ, USA): University of Arizona Press.
Jameson EW, Peeters HJ. 2004. Mammals of California (No. 66). Berkeley (CA, USA): University of California Press.
Johnson ML, Clanton CW. 1954. Natural history of Sorex merriami in Washington State. The Murrelet 35(1): 1-4.
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.
Shaughnessy Jr MJ, Woodman N. 2015. New records of Merriam’s Shrew (Sorex merriami) from western North Dakota. Check List, 11(3), pp.1623-1623.
Verts BJ, Carraway LN. 1998. Land mammals of Oregon. Berkeley (CA, USA): University of California Press.
Wilson DE, Ruff S, editors. 1999. The Smithsonian Book of North American Mammals. Washington D.C. (USA): Smithsonian Institution Scholarly Press.