Sorex monticolus
| Southern Montane Shrew
(Sorex monticolus) | |
|---|---|
| Range | |
 | |
| Taxonomic classification | |
| Order: | Eulipotyphla |
| Suborder: | Erinaceota |
| Superfamily: | Soricoidea |
| Family: | Soricidae |
| Subfamily: | Soricinae |
| Tribe: | Soricini |
| Genus: | Sorex |
| Subgenus: | Otisorex |
| Species group: | Sorex monticolus group |
| Binomial details | |
| Sorex monticolus C. H. Merriam, 1890 | |
| Other resources | |
| Full taxonomic details at MDD | |
The Southern Montane Shrew (Sorex monticolus) is a small- to medium-sized shrew. This species is mainly found in forests and associated with moist areas.
Description
A formal species description for this taxon as delineated by Demboski & Cook (2001) does not currently exist. The following descriptions are provided for portions of the range of Sorex monticolus that Demboski & Cook (2001) retained under this taxon.
From Smith & Belk (1996): "In general, dorsal pelage varies from a dusky brown to gray, ventral pelage is silvery white to gray, and the tail is bicolored without a black tip. Molting occurs twice per year. Juveniles obtain winter pelage during September or October. Timing of molt in spring differs between sexes; females molt from late March to early April, whereas males molt from late May to early August (van Zyll de Jong, 1983). There are clines in body size and intensity of pelage pigmentation, especially among populations in coastal mountain ranges (Findley, 1955)."
From Armstrong et al. (2010) for Colorado: "Dorsal coloration is medium to dark brown, becoming slightly paler on the venter. The tail is bicolored but not conspicuously so." Additionally, "darker winter pelage and paler summer pelage result from spring and fall molts."
From Hoffmeister (1986) for Arizona: "Coloration of upper parts grayish brown; underparts grayish, slightly lighter than upper parts, and hairs usually tipped with ochraceous."
Museum type specimens
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Holotype: USNM 17599/24535. Sorex monticolus. Adult male. San Francisco Mountain, Coconino County, Arizona. Collected 28 August 1889. -
Holotype: USNM 17599/24535. Sorex monticolus. Adult male. San Francisco Mountain, Coconino County, Arizona. Collected 28 August 1889.
Distribution notes
From Androski et al. (2025): "we find that the Southern clade [Sorex monticolus] extends northward throughout Utah and into southern Wyoming. Without denser sampling, we cannot rule out co-occurrence of both the Northern [Sorex obscurus] and Southern [Sorex monticolus] clades in this region. "
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 | Woodman (2012) | head and body: 54–70 (n=21) | 37–51 (n=21) | 12–14 (n=21) | ||
| Arizona (Chiricahua & Santa Catalina Mts.) | Hoffmeister (1986) | 96–188 (n=11) | 38–49 (n=11) | 11.9–13.0 (n=11) | ||
| Arizona (White Mtns.) | Hoffmeister (1986) | 98–113 (n=44) | 37–49 (n=44) | 10–14 (n=44) | ||
| Colorado | Armstrong et al. (2010) | 90–125 | 35–50 | 10–14 | 4–7 | |
| Colorado | Wilson & Ruff (editors, 1999) | 95–116 | 40–49 | 4.4–10.2 |
Skull
| Sorex monticolus skull characters | |
|---|---|
| units in mm | |
| Skull | |
| Condylobasal length: | 16.1–17.7 (Hennings & Hoffman, 1977); 16.1–19.2 (Junge & Hoffman, 1981) ; 16.2–16.7 (Álvarez-Castañeda, 2024) |
| Postmandibular canal: | Absent |
| Shape: | Braincase is rounded |
| Dental | |
| Upper unicuspids: | 5 |
| Unicuspid notes: | U3<U4 |
| Tines present: | Yes |
| Tine size: | Small-medium |
| Tine position: | Below upper limit of pigment on upper incisors |
| Shape upper incisors: | Diverging |
Inner side of lower jaw without postmandibular canal.
From Armstrong et al. (2010): "The braincase is rounded or convex in profile, and the foramen magnum extends farther into the basioccipital than into the supracoccipital. The third unicsupid is smaller than the fourth."
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Holotype: USNM 17599/24535. Sorex monticolus. Adult male. San Francisco Mountain, Coconino County, Arizona. Collected 28 August 1889. Dorsal view of the skull. -
Holotype: USNM 17599/24535. Sorex monticolus. Adult male. San Francisco Mountain, Coconino County, Arizona. Collected 28 August 1889. Ventral view of the skull. -
Holotype: USNM 17599/24535. Sorex monticolus. Adult male. San Francisco Mountain, Coconino County, Arizona. Collected 28 August 1889. Lateral view of the skull. -
Holotype: USNM 17599/24535. Sorex monticolus. Adult male. San Francisco Mountain, Coconino County, Arizona. Collected 28 August 1889. Lateral view of the inner side of the right mandible. -
NEON01IAS. Upper incisors of Sorex monticolus, Boulder County, Colorado, scale is 1 mm.
Taxonomic notes
From Woodman (2018): "Phylogenetic analysis of the mitochondrial cytochrome b gene indicated that S. monticola, as considered by Alexander (1996), is not monophyletic but includes three genetically divergent clades (Demboski and Cook, 2001; Shafer and Stewart, 2007)." According to Demboski & Cook (2001), the “northern continental clade" belongs to the Northern Montane Shrew (Sorex obscurus), and the “southern continental clade” belongs to the Sorex monticolus, and the "coastal clade" belongs to the Pacific Shrew (Sorex pacificus). Further studies will be needed to fully understand new species boundaries and morphological variation.
Nomenclature
Woodman (2018) states: "The name monticola, however, like any species-group name ending in -cola, is an invariable noun in apposition, which does not change gender (Woodman, 2012). The suffix -cola means “dweller” or “inhabitant”; hence, monticola = “mountain dweller.” Merriam (1890:43) made this error when he first described the species as S. monticolus, but he subsequently corrected the spelling to S. monticola (Merriam, 1895:69)."
American Society of Mammalogists Mammal Diversity Database (v1.12.1, accessed June 7, 2024) states: "the spelling is considered to end in -us here rather than -a since the specific epithet is an invariable noun, and although some authors view the original spelling as an error later correct to -a, but this emendation is only justified for names in prevailing use, which is not the case here (the -a spelling is much less common than the -us spelling); includes neomexicanus and previously included S. obscurus."
Similar species
Comparison with Sorex cinereus
From Armstrong et al. (2010): "In Colorado, this shrew can also be confused with the masked shrew [Sorex cinereus], which is strongly resembles in color and general size. However, the teeth of the masked shrew are characterized by a third unicuspid as large as the fourth."
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Southern Montane Shrew (Sorex monticolus) -
Masked Shrew (Sorex cinereus) -
Unicuspids of the Masked Shrew (Sorex cinereus).
Comparison with Sorex obscurus
Distinguishing between Sorex monticolus and the Northern Montane Shrew (Sorex obscurus) in the field may require genetic testing. Currently, the boundaries of Sorex monticolus and Sorex obscurus are not well understood in eastern Idaho, southeastern Wyoming, and northwestern Colorado. Further studies are needed to fully understand species boundaries and morphological variation.
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Southern Montane Shrew (Sorex monticolus) -
Northern Montane Shrew (Sorex obscurus) -
Unicuspids of the Northern Montane Shrew (Sorex obscurus). -
NEON01IAS. Upper incisors of Sorex monticolus, Boulder County, Colorado, scale is 1 mm. -
Upper incisors (I1s) of the Northern Montane Shrew (Sorex obscurus).
Comparison with Sorex vagrans
From Smith & Belk (1996): "Compared with S. vagrans, the toes of S. monticolus are relatively longer and possess a greater number of small paired digital callosities or friction pads. In S. monticolus there are five or six paired friction pads on the second to fourth digits, whereas there are four or fewer in S. vagrans. This character is more evident on the hind feet (van Zyll de Jong, 1982). Cranially, the Vagrant Shrew (Sorex vagrans) can be distinguished from Sorex monticolus by the presence of small tines on the first upper incisors and pigment that does not occur above the dorsal level of the tine; commonly there is a white or pale-colored area between the tine and the body of the tooth (Carraway, 1989).
From Gillihan & Foresman (2004): "Compared to S. monticolus, S. vagrans is generally smaller, with a shorter tail and smaller skull and teeth (van Zyll de Jong 1983). Pigmentation on 11 of S. vagrans extends no further than to dorsal limit of medial accessory cuspules, whereas pigmentation of S. monticolus extends above cuspules (Junge and Hoffmann 1981). Digits 2 through 4 on hind feet of S. vagrans possess 4 or less paired friction pads, whereas those of S. monticolus possess 5 or more pairs (van Zyll de Jong 1982), although this character may not be usable on dried specimens."
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Southern Montane Shrew (Sorex monticolus) -
Vagrant Shrew (Sorex vagrans) -
Upper unicuspids of the Vagrant Shrew (Sorex vagrans) -
NEON01IAS. Upper incisors of Sorex monticolus, Boulder County, Colorado, scale is 1 mm. -
Upper incisors (I1s) of the Vagrant Shrew (Sorex vagrans)
Comparison with other sympatric Sorex
From Smith & Belk (1996): "Sorex monticolus can be distinguished from other sympatric soricids such as S. arizonae, S. arcticus, and S. tundrensis by the relative size of U3 and U4. The U3 is smaller than U4 in S. monticolus, whereas U3 is larger than U4 in the other three species (Junge and Hoffmann, 1981)."
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.
Androski A, Malaney JL, Demboski JR, Liphardt SW, Fernández JA, Cook JA. 2025. Range-wide mitochondrial phylogeography of Sorex monticola: evolutionarily distinct clades occupy divergent abiotic niches. Journal of Mammalogy 106(4):898–932. https://doi.org/10.1093/jmammal/gyaf019
Armstrong, Fitzgerald, J. P., & Meaney, C. A. (2010). Mammals of Colorado, Second Edition. University Press of Colorado.
Carraway LN. 1989. A morphologic and morphometric analysis of the Sorex vagrans species complex in the Pacific Coast region. [PhD thesis]. [Corvallis (OR, USA)]: Oregon State University.
Demboski JR, Cook JA. 2001. Phylogeography of the dusky shrew, Sorex monticolus (Insectivora, Soricidae): insight into deep and shallow history in northwestern North America. Molecular Ecology 10(5): 1227-1240.
Findley JS. 1955. Speciation of the wandering shrew. University of Kansas Publications, Museum of Natural History 9:1-68.
Gillihan SW, Foresman KR. 2004. Sorex vagrans. Mammalian species 744(1): 1–5.
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.
Junge JA, Hoffman RS. 1981. An annotated key to the long-tailed shrews (Genus Sorex) of the United States and Canada with notes on middle American Sorex. Occasional Papers of the Museum of Natural History, The University of Kansas, Lawrence Kansas. Number 94; Pages 1-48.
Mammal Diversity Database. 2023. Mammal Diversity Database (Version 1.12.1) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.10595931 DOI. Downloaded July 7, 2024.
Merriam CH. 1890. Results of a Biological Survey of the San Francisco Mountain Region and Desert of the Little Colorado, Arizona. North American Fauna 3, 43.
Merriam CH, 1895. Synopsis of the American Shrews of the Genus Sorex. North American Fauna 10:57–98: pls. 4–12.
Naughton D. 2012. The natural history of Canadian mammals. Toronto (ON, CA): University of Toronto Press.
Smith ME, Belk MC. 1996. Sorex monticolus. Mammalian Species (528): 1-5.
van Zyll de Jong CG. 1982. An additional morphological character useful in distinguishing two similar shrews Sorex monticolus and Sorex vagrans. The Canadian Field-Naturalist, 96:349-350.
van Zyll de Jong CG. 1983. Handbook of Canadian mammals-marsupials and insectivores. National Museums of Canada, Ottawa, 1:1- 210.
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.
Woodman N. 2012. Taxonomic Status and Relationships of Sorex obscurus parvidens Jackson, 1921, from California. Journal of Mammalogy 93(3): 826–838.
Woodman N. 2018. American Recent Eulipotyphla: Nesophontids, Solenodons, Moles, and Shrews in the New World. Smithsonian Institution Scholarly Press. Book. https://doi.org/10.5479/si.1943-6696.650