Sorex rohweri
| Olympic Shrew
(Sorex rohweri) | |
|---|---|
| Range | |
 | |
| Taxonomic classification | |
| Order: | Eulipotyphla |
| Suborder: | Erinaceota |
| Family: | Soricidae |
| Subfamily: | Soricinae |
| Tribe: | Soricini |
| Genus: | Sorex |
| Subgenus: | Otisorex |
| Species group: | Sorex cinereus group |
| Binomial details | |
| Sorex rohweri R. L. Rausch, Feagin, & V. R. Rausch, 2007 | |
| Other resources | |
| Full taxonomic details at MDD | |
Description
Nagorsen and Panter (2009) provide the following diagnostic qualitative traits for identifying Sorex rohweri from the lower Fraser River basin of British Columbia: "it is a small shrew with a dorsal coloration that is brown in the summer and dark grey in the winter. It has a strongly bicolored tail. There are five paired toe pads on the 3rd 4th digits of the hind foot. The third unicuspid is equal or slightly shorter than the fourth unicuspid. The medial edge of the upper incisors are curved. The medial tine on the upper incisors is minute and positioned at or above the upper pigment edge."
From Woodman & Fisher (2016): "tail strongly bicolored; paired digital callosities on pedal digits I-V: 4-5-5-5-3."
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 (southwestern) | Nagorsen and Panter (2009) | 91–109 (n=14) | 32–50 (n=17) | 8–13 (n=17) | 2.5–6.0 (n=6) | |
| Oregon and Washington | Woodman and Fisher (2016) | 84–113 (n=42) | 37–49 (n=42) | 10–13 (n=42) |
Skull
| Sorex rohweri skull characters | |
|---|---|
| units in mm | |
| Skull | |
| Condylobasal length: | 14.7–16.6 (Woodman & Fisher 2016) |
| Postmandibular canal: | Present |
| Dental | |
| Upper unicuspids: | 5 |
| Unicuspid notes: | U3<U4 |
| Tines present: | Yes |
| Tine size: | Tiny |
| Tine position: | At or above the upper pigment edge |
| Shape upper incisors: | Diverging; slightly curved |
| Dental characters: | Tines are are weak and often difficult to discern; pigmentation is pale or lacking (Woodman & Fisher, 2016) |
From Woodman & Fisher (2016): "Viewed anteriorly, the medial edges of the upper first incisors (I1s) of S. rohweri tend to diverge greatly, forming an angle of up to 45° (Rausch et al. 2007). In S. cinereus and S. vagrans, however, the medial edges of I1s are typically straight and appear approximately parallel or diverge only slightly. The medial tine on the I1 of S. rohweri is weak and often difficult to discern; pigmentation is pale or lacking. The medial tine is located proximal to the margin of pigmentation on the primary cusp of the tooth. In contrast, the medial tines of S. cinereus and S. vagrans are typically obvious and noticeably pigmented (strongly pigmented in S. vagrans). In S. cinereus, the medial tine extends well distal to the margin of pigmentation on the body of I1. In S. vagrans, the medial tine is positioned at or proximal to the margin of pigmentation. In occlusal view, the unicuspid toothrows of S. rohweri and S. cinereus appear long, straight, and even, and the individual teeth generally diminish in size from the first unicuspid (U1) to the fifth (U5). In S. rohweri, U3 and U4 may appear equal in length, but the posterior edge of U3 is typically narrower than the neighboring anterior margin of U4. In S. c. cinereus, U3 is slightly longer and narrower than U4, whereas, in S. c. streatori, U3 is slightly longer, but typically as wide as, or wider than, U4. In contrast, the unicuspid tooth-row of S. vagrans is relatively short and irregular, with U3 noticeably shorter and slightly narrower than U4. Pigmentation of the dentition of S. rohweri is typically paler overall than in S. cinereus and S. vagrans. The lingual ridge, which extends from the main cusp to the lingual cingulum on U1-U4 (Junge & Hoffman 1981), is typically unpigmented in S. rohweri, palely pigmented in S. c. cinereus, and darkly pigmented in S. c. streatori and S. vagrans. On the first lower incisor (il) of S. rohweri and S. cinereus, the pigment on the distal end of the tooth is separated from the pigment on the two more proximal denticles, whereas, in S. vagrans, pigmentation is continuous from the distal tip to both denticles."
-
Lateral view of the skull of Sorex rohweri. The skull is a bit damaged; the left tympanic ring is missing and the right tympanic ring is damaged and hanging down. Long scale bar represents 1 cm; the short scale bar represents 1 mm. -
unicuspids of Sorex rohweri, scale is 1 mm. -
Upper incisors of Sorex rohweri, scale is 1 mm.
Similar species
From Woodman and Fisher (2016): Morphometric analysis “indicate that S. rohweri and S. c. cinereus (WA and southwest British Columbia) are more similar in external dimensions, and both taxa are considerably smaller than either S. c. streatori (AK and northwest British Columbia) or S. vagrans. Regardless, individual measurements overlap greatly among S. rohweri, S. cinereus, and S. vagrans in the Pacific Northwest and alone provide little assistance in differentiating these species. Instead, a suite of cranio-dental and external characters is most useful in distinguishing these species (see Rausch et al. 2007, Nagorsen and Panter 2009). Viewed anteriorly, the medial edges of the upper first incisors (I1s) of S. rohweri tend to diverge greatly, forming an angle up to 45 degrees (Rausch et al. 2007). In S. cinereus and S. vagrans, however, the medial edges of I1s are typically straight and appear approximately parallel of diverge only slightly.” The medial tine on the upper incisors is often difficult to discern, whereas the medial tines on the upper incisors of S. cinereus and S. vagrans are typically obvious and noticeably pigmented. In S. cinereus, the medial tine is positioned well below the margin of pigmentation on the upper incisors. In S. vagrans, the medial tine is positioned at or proximal to the margin of pigmentation. In side view, the upper unicuspids in S. cinereus and S. vagrans appear straight, even, and “generally diminish in size from the first unicuspid (U1) to the fifth unicuspid (U5). In S. rohweri, U3 and U4 may appear equal in length, but the posterior edge of U3 is typically narrower than the neighboring anterior margin of U4... The plantar surface of pedal digits II—IV of S. rohweri each possesses five paired digital callosities (friction pads), whereas, there are six pairs in S. cinereus, and four or fewer in S. vagrans (van Zyll de Jong 1982, Nagorsen and Panter 2009)."
References
Nagorsen DW, Panter N. 2009. Identification and status of the Olympic shrew (Sorex rohweri) in British Columbia. Northwestern Naturalist 90(2): 117-129.
Rausch RL, Feagin JE, Rausch VR. 2007. Sorex rohweri sp. nov. (Mammalia, Soricidae) from northwestern North America. Mammalian Biology 72:93–105.
van Zyll de Jong CG. 1982. An additional morphological character useful in distinguishing two similar shrews Sorex monticolus and Sorex vagrans. Canadian Field-Naturalist 96:349–350.
Woodman N, Fisher RD. 2016. Identification and distribution of the Olympic Shrew (Eulipotyphla: Soricidae), Sorex rohweri Rausch et al., 2007 in Oregon and Washington, based on USNM specimens. Proceedings of the Biological Society of Washington 129(1): 84-102.