Sorex dispar

Rock Shrew
(*Sorex dispar*)
Rock Shrew (Sorex dispar)
Range
Taxonomic classification
Order:	Eulipotyphla
Suborder:	Erinaceota
Family:	Soricidae
Subfamily:	Soricinae
Tribe:	Soricini
Genus:	Sorex
Subgenus:	Otisorex
Species group:	Sorex dispar group
Binomial details
	Sorex dispar Batchelder, 1911
Other resources
	Full taxonomic details at MDD

Description

From Best & Hunt (2020): "The long-tailed shrew [or rock shrew] is a small, slender shrew with a relatively long tail that is 80-90% of the length of head and body combined. Dorsal pelage is slate gray to brownish and ventral pelage is slightly paler. The tail is well furred and not distinctly bicolored, and hairs are lost from the tail with age. The long-tailed shrew may be distinguished by its slimmer body and relatively longer tail from the smoky shrew."

From Naughton (2012): "Long-tailed shrews [or rock shrews] are slender, slate-grey shrews with long, fairly thick tails that comprise 50% of the total length. Pelage on the back and belly is usually the same colour during both winter and summer, but some individuals may be slightly paler on the underside during summer. Feet are pale. Tails are indistinctly bicoloured, darker above and lighter below. Tail fur commonly wears off as the animals age, so that older adults may have naked tails. Vibrissae (whiskers) are long."

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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	Mass
Canada	Naughton (2012)	95–136	45–67	11–15	2.3–8.3
Carolinas, Virginia, Maryland	Webster et al. (1985)	114–132	49–59	14–15
Great Lakes Region	Kurta (2017)	110–135	50–64	14–15	4–6
northern part of range	Kirkland & Van Deusen (1979)	103–137 (n>150)	46–65 (n>150)	12.0–15.5 (n>150)
rangewide	Wilson & Ruff (editors, 1999)	103–136	46–67		3.1–8.3
southern Appalachians	Whitaker Jr. & Hamilton Jr. (1998)	108–135	49–67	13.5–18	3.1–3.8
Virginia	Linzey (1998)	110–132	50–59		4–8

Skull

Sorex dispar skull characters

units in mm

Skull

Condylobasal length:	15.8–18.5 (Hall & Kelson, 1959); 16.45–18.7 (Kirkland, 1981); 15.35–18.7 (S. d. gaspensis; Kirkland, 1981); 18.4–19.2 (Álvarez-Castañeda, 2024)
Postmandibular canal:	Absent
Shape:	Rostrum shallow; braincase bulbous; posterior border of the infraorbital foramen behind the space between the M1 and M2; mental foramen level with the space between p4 and m1

Dental

Upper unicuspids:	5
Unicuspid notes:	U3≥U4
Tines present:	Yes
Tine size:	Tiny
Tine position:	At or just below the upper limit of pigment on upper incisors
Shape upper incisors:	Diverging

From Naughton (2012): "Only four of the upper unicsupids are readily apparent, the fifth being highly reduced. The fourth upper unicuspid is noticeably smaller than the third."

There are five unicuspids, first and second are largest and nearly equal in size, third is slightly larger than fourth and both are smaller than first and second, and fifth is minute.

Dorsal view of the skull of Sorex dispar.
Ventral view of the skull of Sorex dispar.
Lateral view of the skull of Sorex dispar. Short scale bar is 1 mm; long scale bar is 1 cm.
Unicuspids of Sorex dispar. Scale bar is 1 mm.
Upper incisors of Sorex dispar. Scale bar is 1 mm.

Subspecies

Subspecies designations and identifications are detailed in Diersing (2019).

Distribution of the subspecies of Sorex dispar. Figure borrowed from Diersing (2019). "Figure 3. A map of the Appalachian Region of northeastern North America showing the geographic distribution of Sorex d. dispar (dots), S. d. kirklandi (open circles), and S. d. gaspensis (filled squares). Numbers are pooled samples (see Table 1 and Appendix I for geographic area covered for each sample and list of specimens included in the sample, respectively)."

Taxonomic notes

From Woodman (2018): "Analyses of mitochondrial and nuclear genetic markers among populations of S. dispar and S. gaspensis have indicated that they represent a single monophyletic group lacking any genetic structuring sufficient for either species or subspecies recognition (Rhymer et al., 2004; Shafer et al., 2008). Instead, the smaller body size of S. gaspensis appears to reflect a continuation of a cline of gradually decreasing body size from south to north (Rhymer et al., 2004), a conclusion consistent with those of Kirkland and Van Deusen (1979) and Scott and van Zyll de Jong (1989)."

Similar species

If only the skull is available, Sorex dispar can be separated from S. fumeus and S. cinereus 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). Comparison of the skulls of Sorex dispar, S. cinereus and S. fumeus below.

In Sorex 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).
The anterior margin of the zygomatic plate in the Masked Shrew (Sorex cinereus) is located over posterior end of the first molar (M1). Based on Diersing (2019).
The anterior margin of the zygomatic plate in the Smoky Shrew (Sorex fumeus) is located over posterior end of the first molar (M1). Based on Naughton (2012).

Upper incisors of Sorex dispar, scale is 1 mm.
Upper incisors of the Masked Shrew (Sorex cinereus).
Upper incisors of the Smoky Shrew (Sorex fumeus), scale is 1 mm.

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.

Batchelder CF. 1911-05-15. A new name for Sorex macrurus Batchelder. Proceedings of the Biological Society of Washington 24:97.

Best TL, Hunt JL. 2020. Mammals of the southeastern United States. Tuscaloosa (AL, USA): University Alabama Press.

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): pp.1837-1846.

Kirkland GL, Van Deusen HM. 1979. The shrews of the Sorex dispar group: Sorex dispar Batchelder and Sorex gaspensis Anthony and Goodwin. American Museum Novitates; no. 2675.

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.

Naughton D. 2012. The natural history of Canadian mammals. Toronto (ON, CA): University of Toronto Press.

Rhymer JM, Barbay JM, Givens HL. 2004. Taxonomic relationship between Sorex dispar and S. gaspensis: inferences from mitochondrial DNA sequences. Journal of Mammalogy 85(2): 331-337.

Scott FW, van Zyll de Jong CG. 1989. New Nova Scotia records of the long-tailed shrew, Sorex dispar, with comments on the taxonomic status of Sorex dispar and Sorex gaspensis. Naturaliste Canadien 116:145–154.

Shafer AB, Scott FW, Petersen SD, Rhymer JM, Stewart DT. 2008. Following the SINEs: a taxonomic revision of the long-tailed shrew complex, Sorex dispar and S. gaspensis. Journal of Mammalogy 89(6): 1421-1427.

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, Hamilton WJ. 1998. Mammals of the eastern United States. Ithaca, (NY, USA): Cornell University Press.

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. Smithsonian Institution Scholarly Press. Book. https://doi.org/10.5479/si.1943-6696.650