Sorex trowbridgii
| Trowbridge's Shrew
(Sorex trowbridgii) | |
|---|---|
| Range | |
 | |
| Taxonomic classification | |
| Order: | Eulipotyphla |
| Suborder: | Erinaceota |
| Superfamily: | Soricoidea |
| Family: | Soricidae |
| Subfamily: | Soricinae |
| Tribe: | Soricini |
| Genus: | Sorex |
| Subgenus: | Incertae sedis |
| Species group: | Sorex trowbridgii group |
| Binomial details | |
| Sorex trowbridgii S. F. Baird, 1857 | |
| Other resources | |
| Full taxonomic details at MDD | |
Description
From George (1989): "Sorex trowbridgii is a medium-sized, long-tailed shrew (Jackson, 1928). The species has a dark gray pelage slightly more brownish in summer than in winter. Whiskers are numerous and moderately long. The ears are almost hidden by the pelage. The tail is hairy in young animals, becoming naked as individuals age. The feet are pentadactylous, as in all Sorex, and vary in color "from whitish to very light tan" (Maser et al., 1981:61)."
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 |
|---|---|---|---|---|---|---|
| British Columbia | Wilson & Ruff (editors, 1999) | 104–124 | 50–59 | |||
| California | Jameson & Peeters (2004) | 95–132 | 40–62 | 12–15 | 6–8 | 4.8 |
| California | Wilson & Ruff (editors, 1999) | 114–131 | 48–56 | 3.8–5 | ||
| Canada | Naughton (2012) | 101–128 | 41–62 | 10–15 | 5–8 | 3.8–8.0 |
| Oregon | Verts & Carraway (1998) | 99–132 | 46–60 | 11–14 | 2.9–6.7 |
Color variation
This section shows some of the color variation present in Sorex trowbridgii. 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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NEON01IVJ. Sorex trowbridgii. Early May. Location: Skamania County, Washington. -
NEON05G3C. Sorex trowbridgii. Early June. Location: Clark County, Washington. -
NEON01IQX. Sorex trowbridgii. Late June. Location: Clark County, Washington. -
NEON01ITE. Sorex trowbridgii. Early September. Location: Skamania County, Washington. -
NEON01ISY. Sorex trowbridgii. Late September. Location: Clark County, Washington. -
NEON01ISV. Sorex trowbridgii. Late September. Location: Clark County, Washington. -
NEON01IHK. Sorex trowbridgii. Mid-September. Location: Fresno County, California. -
NEON01IYG. Sorex trowbridgii. Late September. Location: Fresno County, California.
Skull
| Sorex trowbridgii skull characters | |
|---|---|
| units in mm | |
| Skull | |
| Condylobasal length: | 16.8–18.8 (see George, 1989 for citations); 16.8–17.5 (Álvarez-Castañeda, 2024) |
| Postmandibular canal: | Present |
| 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 and curved |
The inside of the lower mandible contains a postmandibular canal. Usually, the inferior dentary foramen and postmandibular foramen are confluent and large (Naughton, 2012). The inner (median) surface of the unicupid teeth lack a pigmented ridge. The third unicuspid is smaller (shorter) than fourth unicuspid. The medial edge of the upper incisors are curved. The medial tine on the upper incisors is positioned at or just below the upper edge of pigment.
From George (1981): "The third unicuspid is smaller than the fourth (Jackson, 1928; Junge and Hoffmann, 1979). Trowbridge's shrews usually possess a post-mandibular foramen; the orbit is placed relatively far back at the level of the metastyle of M2; the lacrimal foramen is at the interface of Ml and M2; and the border of the infraorbital foramen is on a line between the mesostyle and metastyle of Ml (Carraway, 1987; Junge and Hoffmann, 1979; van Zyll de Jong, 1983)."
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Lectotype: USNM 813. Sorex trowbridgii trowbridgii. Male. Astoria, Clatsop County, Oregon. -
NEON01IYG. Lateral view of the skull of Sorex trowbridgii. Left tympanic ring is missing. Long scale bar is 1 cm; short scale bar is 1 mm. -
NEON01IYG. Unicuspids of Sorex trowbridgii, scale is 1 mm. -
NEON01IYG. Upper incisors of Sorex trowbridgii from California, scale is 1 mm. -
MVZ:Mamm:219772. Upper incisors of Sorex trowbridgii from California, scale is 1 mm.
Similar species
Comparison with Sorex obscurus
Distinguishing between the Sorex trowbridgii and Northern Montane Shrew (Sorex obscurus) in the field may be easy or challenging depending on the locality, season, and age of the individual. The pelage of Sorex obscurus ranges from dark grayish brown to brown and that of Sorex trowbridgii ranges from dark gray pelage in winter to slightly more brownish in summer (George, 1989; Naughton, 2012). Careful examination of the skull may be required in order to be certain of identification. In Sorex trowbridgii, the inside of the lower mandible contains a postmandibular canal; the inferior dentary foramen and postmandibular foramen are confluent and large (Naughton, 2012); and the medial edge of the upper incisors are curved. Whereas in Sorex obscurus the lower mandible lacks a postmandibular canal and the medial edges of the upper incisors are not curved.
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NEON01IUE. Northern Montane Shrew (Sorex obscurus). Early October in Skamania County, Washington. -
NEON05JT2. Northern Montane Shrew (Sorex obscurus). Early September in Clark County, Washington. -
NEON01IHK. Trowbridge's Shrew (Sorex trowbridgii). Mid-September in Fresno County, California. -
NEON05G3C. Trowbridge's Shrew (Sorex trowbridgii). Early June in Clark County, Washington. -
NEON03P7V. Unicuspids of the Northern Montane Shrew (Sorex obscurus). Similar to Sorex trowbridgii, the third unicuspid is smaller than the fourth. -
NEON01IYG. Unicuspids of the Trowbridge's Shrew (Sorex trowbridgii). Similar to Sorex obscurus, the third unicuspid is smaller than the fourth. -
Upper incisors (I1s) of the Northern Montane Shrew (Sorex obscurus) from Denali Borough, Alaska. Scale is 1 mm. The medial edge of the upper incisors are straight (not curved). -
MVZ:Mamm:219772. Upper incisors (I1s) of the Trowbridge's Shrew (Sorex trowbridgii) from California, scale is 1 mm. The medial edge of the upper incisors are curved.
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.
Baird SF. 1857. Mammals. In Reports of Explorations and Surveys to Ascertain the Most Practicable and Economical Route for a Railroad from the Mississippi River to the Pacific Ocean. Part 1. General Report upon the Zoology of the Several Pacific Railroad Routes, Volume 8, bk. 1. Washington, D.C., Beverly Tucker, 13.
Carraway LN. 1987. Analysis of characters for distinguishing Sorex trowbridgii from sympatric S. vagrans. Murrelet 68:29-30.
George SB. 1989. Sorex trowbridgii. Mammalian Species (337): 1-5.
Jackson HHT. 1928. A taxonomic review of the American long-tailed shrews (genera Sorex and Microsorex). North American Fauna 51: 1-238.
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.
Maser C, Mate BR, Franklin JF, Dyrness CT. 1981. Natural history of Oregon coast mammals. U.S. Dept. Agric., Forest Serv., Gen. Tech. Rept., PNW-133:1-496.
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.
van Zyll de Jong CG. 1983. Handbook of Canadian mammals. 1. Marsupials and insectivores. Ottawa (ON, CA): National Museum of Canada. 210 pp.
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.