Sorex sonomae
| Fog Shrew
(Sorex sonomae) | |
|---|---|
| Range | |
 | |
| Taxonomic classification | |
| Order: | Eulipotyphla |
| Suborder: | Erinaceota |
| Family: | Soricidae |
| Subfamily: | Soricinae |
| Tribe: | Soricini |
| Genus: | Sorex |
| Subgenus: | Otisorex |
| Species group: | Sorex sonomae group |
| Binomial details | |
| Sorex sonomae H. H. T. Jackson, 1921 | |
| Other resources | |
| Full taxonomic details at MDD | |
Description
From Jameson & Peeters (2004): "A large shrew distinguished by its reddish, light brown color and absence of median tine on upper incisors."
From Verts & Carraway (1998): "Two geographic races are recognized (Carraway, 1990); both occur in Oregon... Adults of S. s. sonomae are light dark-brown on the dorsum and dark brown on the venter; bases of dorsal hairs are neutral black, neutral very dark-gray on the venter. Subadults are slightly lighter. All surfaces of the tail are the same color as the dorsum. Adults of S. s. tenelloidus are medium brown to dark gray on the dorsum, pinkish white on the venter; the tail is indistinctly bicolored, medium brown above and pinkish white below." Additionally, ''S. sonomae has four friction pads on the second through fourth toes of the hind foot (Carraway, 1990)."
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 |
|---|---|---|---|---|---|---|
| California | Jameson & Peeters (2004) | 120–158 | 45–65 | 13–18 | 7–8 | 14–18 |
| Oregon (Cascade Range) | Verts & Carraway (1998) | 106–145 | 41–66 | 12–17 | 5.0–12.7 | |
| Oregon (Coast Range) | Verts & Carraway (1998) | 105–153 | 45–69 | 15–19 | 6.3–12.8 | |
| rangewide | Wilson & Ruff (editors, 1999) | 105–180 | 36–85 | 5.5–15 |
Skull
| Sorex sonomae skull characters | |
|---|---|
| units in mm | |
| Skull | |
| Condylobasal length: | S. s. sonomae: 19.34–23.22 (Carraway, 1989); S. s. tenelliodus: 16.5–20.21 (Carraway, 1989) |
| Postmandibular canal: | Absent |
| Shape: | Braincase is rounded |
| Dental | |
| Upper unicuspids: | 5 |
| Unicuspid notes: | U3<U4; U5 usually rectangular |
| Tines present: | No |
| Shape upper incisors: | Parallel |
| Dental characters: | Unicuspids appear somewhat bulbous; fifth unicuspid is usually rectangular and is separated from the fourth premolar by a gap (Verts & Carrawy, 1998) |
From Verts & Carraway (1998): "It [Sorex sonomae] may be distinguished from congeners in Oregon by the third unicuspid being smaller than the fourth combined with the absence of tines or other projections on the first upper incisors, permitting them to be appressed for most or all of the length of the pigmented portion. The fifth upper unicuspid is usually rectangular and is separated from the fourth premolar by a gap. The zygomatic process of the maxillary usually is rounded."
-
Lateral view of the skull of Sorex sonomae from Lane County, Oregon. Long scale bar is 1 cm. -
Upper incisors of Sorex sonomae from Lane County, Oregon. Scale is 1 mm. -
Upper incisors of Sorex sonomae from Lane County, Oregon. Scale is 1 mm. -
Unicuspids (slightly worn) of Sorex sonomae, scale is 1 mm.
Habitat
From Carraway (1989): "The distribution of S. sonomae is restricted primarily to the fog belt (usually 150 to 200 cm precipitation per year; Loy, 1976) of the California and Oregon coastlines."
Subspecies
Two subspecies are recognized for Sorex sonomae: Sorex sonomae sonomae and Sorex sonomae tenelloidus.
Sorex sonomae sonomae
Distribution for Sorex sonomae sonomae from Woodman (2008): "USA: Pacific Coast from Lincoln and Benton Counties, Oregon, south to Marin County, California; elevational distribution: from near sea level to 1,700 m (Carraway, 1990)."
Description of Sorex sonomae sonomae from Carraway (1989): "Sorex s. sonomae is the largest of the Pacific Coast brown shrews. In adults, the dorsal pelage, based on 20 specimens collected in August, is light dark-brown (<7.5YR 3/2; Mummy Brown of Ridgeway [1912]); the ventral pelage is dark brown (7.5YR 3/2) to Saccardo's Umber (no comparable Munsell color). Bases of hairs are neutral black (7.5YR N2/0) on the dorsum and neutral very-dark-gray (7.5YR N3/0) on the venter. Flank glands of 10 adult males in the same sample are covered with bristles colored Saccardo's Umber. In 20 subadults obtained in August, the dorsal pelage is medium light-brown (between 7.5YR 4/2 and 7.5YR 4/4 [Munsell Color, 1975]; Sepia of Ridgeway [1912]) and the ventral pelage is Saccardo's Umber (no comparable Munsell color). The entire tail is colored the same as the dorsum in all age classes. There are four pairs of digital friction pads on the second to fourth toes of the hind feet."
Sorex sonomae tenelliodus
Distribution for Sorex sonomae tenelloidus from Woodman (2008): USA: Lincoln County, Oregon, south to northern Siskiyou County, California; elevational distribution: 160–1,315 m (Carraway, 1990)."
Description of Sorex sonomae tenelliodus from Carraway (1989): "Overall, S. s. tenelliodus is smaller and lighter in color than S. s. sonomae. The dorsal and ventral pelages of three specimens collected in May and September are medium brown (7.5YR 4/2; Munsell Color, 1975) to dark gray (5YR 4/1) and pinkish white (5YR 8/2), respectively. Bases of hairs on both dorsum and venter are neutral dark-gray (7.5YR N4/0). The tail is indistinctly bicolored, medium-brown above and pinkish-white (7.5YR 8/2) below, not unicolored as in S. s. sonomae. Flank glands on one adult male collected in May were covered with pinkish-white bristles. There are four pairs of digital friction pads on the second to fourth toes of the hind feet."
Similar species
Sorex sonomae can be distinguished from all other Sorex species in the US by the lack of tines on the upper incisors and the medial edge of the upper incisors being parallel. Sorex sonomae also lack tines on the upper incisors but only the tips of upper incisors are close together since the teeth converge distally.
-
Upper incisors of Sorex sonomae. Scale is 1 mm. -
Upper incisors of Merriam's Shrew (Sorex merriami). Borrowed from Diersing & Hoffmeister (1977).
References
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.
Carraway LN. 1990. A Morphometric Analysis of the "Sorex Vagrans Species Complex" in the Pacific Coast Region. Texas Tech University Press.
Jackson HHT. 1921. Two unrecognized shrews from California. Journal of Mammalogy 2(3): 162.
Jameson EW, Peeters HJ. 2004. Mammals of California (No. 66). Berkeley (CA, USA): University of California Press.
Loy WG (ed.). 1976. Atlas of Oregon. University Oregon Books, Eugene, 215 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.