Sorex hoyi
| Eastern Pygmy Shrew
(Sorex hoyi) | |
|---|---|
| Range | |
 | |
| Taxonomic classification | |
| Order: | Eulipotyphla |
| Suborder: | Erinaceota |
| Family: | Soricidae |
| Subfamily: | Soricinae |
| Tribe: | Soricini |
| Genus: | Sorex |
| Subgenus: | Otisorex |
| Species group: | Sorex hoyi group |
| Binomial details | |
| Sorex hoyi S. F. Baird, 1857 | |
| Other resources | |
| Full taxonomic details at MDD | |
Sorex hoyi was split by Hope et al. (2020); Sorex eximius represents the western species of the pygmy shrew and Sorex hoyi represents the eastern species of the pygmy shrew.
Description
Small reddish brown to grayish brown. Ventral coloration is lighter, ranging from grayish to buffy brown. Tail is indistinctly bicolored. Winter coloration is grayer and underparts are whitish.
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 |
|---|---|---|---|---|---|---|
| Alabama (Jackson Co.) | Best & Dusi (2014) | 61–77 (n=5) | 23–27 (n=5) | 9 (n=5) | 2.1–3.0 | |
| Carolinas, Virginia, Maryland | Webster et al. (1985) | 70–86 | 25–33 | 7–10 | ||
| Great Lakes Region | Kurta (2017) | 80–91 | 27–33 | 8–10.5 | 2–4 | |
| Indiana (south-central region) | Whitaker Jr. & Hamilton Jr. (1998) | 71–82 (n=71) | 21–28 (n=71) | 6–9 (n=71) | 1.3–2.9 (n=71) | |
| Maine | Whitaker Jr. & Hamilton Jr. (1998) | 85 (n=13) | 29.5 (n=13) | 9.4 (n=13) | 2.5–3 (n=13) | |
| Minnesota | Hazard (1982) | 75–91 | 27–34 | 8–11.5 | 3–6 | 2.9–4.2 (n=3) |
| Ontario | Wilson & Ruff (editors, 1999) | 62–106 | 21–39 | 21–7.3 | ||
| Virginia | Linzey (1998) | 70–85 | 25–30 | 2–4 |
Skull
| Sorex hoyi skull characters | |
|---|---|
| units in mm | |
| Skull | |
| Condylobasal length: | 13.0–15.8 (Hall & Kelson, 1959); 14.3–15.0 (Álvarez-Castañeda, 2024) |
| Postmandibular canal: | Absent |
| Shape: | Braincase is rounded |
| Dental | |
| Upper unicuspids: | 5 |
| Unicuspid notes: | U3 and U5 are tiny and vestigial |
| Tines present: | Yes |
| Tine size: | Large and long |
| Tine position: | Well below upper limit of pigment on upper incisors |
| Shape upper incisors: | Slightly curved |
| Dental characters: | U3 and U5 are barely or not at all visible in side view, but may be seen in occlusal view |
Sorex hoyi have five upper unicuspids. The first, second, and fourth unicuspids are clearly visible. The third and fifth unicuspids are tiny and vestigial. The medial tines on the upper incisors are large and well within the pigmented area.
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Dorsal view of the skull of Sorex hoyi. Long scale bar is 1 cm. -
Ventral view of the skull of Sorex hoyi. Long scale bar is 1 cm. -
Lateral view of the skull of Sorex hoyi from north-central Minnesota. Long scale bar is 1 cm. -
Lateral view of the skull of Sorex hoyi from southeastern Manitoba, Canada. The individual shown is a subadult as the cranial plates have not fully joined. Long scale bar is 1 cm. -
Lateral view of the skull of Sorex hoyi from north-central Wisconsin. The individual shown is an adult with worn teeth. Long scale bar is 1 cm. -
Upper unicuspids of Sorex hoyi. In this individual, the third unicuspid (U3) is tiny and not visible in side view. The fifth unicuspid (U5) is also tiny and just barely visible. Note that this is an old individual and the teeth are worn. In some individuals, the third unicuspid may be barely visible in side view, while the fifth is not. -
Upper incisors of Sorex hoyi.
Similar species
Comparison with Sorex eximius
From Hope et al. (2020): "Until more definitive criteria become available, distinguishing between the two distinct North American pygmy shrews (S. eximius and S. hoyi) remains problematic in a field setting. We suggest careful consideration of the known geographical extent of genetic lineages based on the present study and emphasize the need for further field sampling through regions of potential sympatry. These areas include North Dakota, Minnesota, Manitoba and Saskatchewan, in addition to further north around Hudson Bay and the Gaspe Peninsula. Given the small size of North American pygmy shrews and high variance associated with the measurement of tiny mammals (Stephens et al., 2015), it is unlikely that standard field measurements alone will distinguish these species reliably. More detailed skeletal analyses based on samples with known a priori genetic identity may resolve diagnostic differences (Nagorsen et al., 2017), and field-based molecular barcoding is increasingly tractable (Ivanova et al., 2012)."
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Range of Sorex eximius -
Range of Sorex hoyi
Comparison with other sympatric shrews
Differentiating Sorex hoyi in the field from other sympatric brown shrews may be difficult. Correct identification will likely require careful examination of the unicuspids. The third and fifth unicuspids in Sorex hoyi and Sorex eximius are tiny and not clearly visible, whereas the third unicuspid in other sympatric brown shrews are clearly visible in lateral view.
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Unicuspids of Sorex hoyi. Notice that U3 and U5 are tiny are not clearly visible. On this specimen, U3 is not visible in lateral view. -
Unicuspids of Sorex cinereus for comparison. Notice that U3 is clearly visible. The third and fifth unicuspids in Sorex eximius and Sorex hoyi are tiny and not clearly visible, whereas the third unicuspid in other sympatric brown shrews are clearly visible in lateral view.
References
Baird SF. 1857. General Report upon the Zoology of the Several Pacific Railroad Routes. Part I. Mammals. A. P. Nicholson, Washington, 757 pp.
Best TL, Dusi JL. 2014. Mammals of Alabama (Vol. 4). Tuscaloosa (AL, USA): University Alabama Press.
Hazard EB. 1982. The mammals of Minnesota. Minneapolis (MN, USA): University of Minnesota Press.
Hope AG, Stephens RB, Mueller SD, Tkach VV, Demboski JR. 2020. Speciation of North American pygmy shrews (Eulipotyphla: Soricidae) supports spatial but not temporal congruence of diversification among boreal species. Biological Journal of the Linnean Society 129(1): 41-60.
Ivanova NV, Clare EL, Borisenko AV. 2012. DNA barcoding in mammals. DNA barcodes: Methods and protocols pp.153-182.
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.
Stephens RB, Karau KH, Yahnke CJ, Wendt SR, Rowe RJ. 2015. Dead mice can grow–variation of standard external mammal measurements from live and three postmortem body states. Journal of Mammalogy 96(1): 185-193.
Webster WD, Parnell JF, Biggs WC. 1985. Mammals of the Carolinas, Virginia, and Maryland. Chapel Hill (NC, USA): University of North Carolina Press.
Wilson DE, Ruff S, editors. 1999. The Smithsonian Book of North American Mammals. Washington D.C. (USA): Smithsonian Institution Scholarly Press.