Sorex palustris
| American Water Shrew
(Sorex palustris) | |
|---|---|
| Range | |
 | |
| Taxonomic classification | |
| Order: | Eulipotyphla |
| Suborder: | Erinaceota |
| Family: | Soricidae |
| Subfamily: | Soricinae |
| Tribe: | Soricini |
| Genus: | Sorex |
| Subgenus: | Otisorex |
| Species group: | Sorex palustris group |
| Binomial details | |
| Sorex palustris J. Richardson, 1828 | |
| Other resources | |
| Full taxonomic details at MDD | |
Sorex palustris was split by Hope et al. (2014).
From Woodman (2018): "Hope et al.’s (2014) investigation of the molecular phylogenetics of North American water shrews revealed three species-level clades among the subspecies formerly united as Sorex palustris: eastern Sorex albibarbis, western cordilleran Sorex navigator, and boreal Sorex palustris (sensu stricto). Nagorsen et al. (2017) demonstrated that parapatric S. navigator and S. palustris can be distinguished morphometrically."
Description
From Beneski & Stinson (1987): "Sorex palustris is a large shrew with measurements of adults (in mm) ranging as follows: total length, 130 to 170; tail length, 57 to 89; length of hind foot, 18 to 22 (Ingles, 1965; Johnson, 1951; van Zyll de Jong, 1983). The tail is distinctly bicolored (dark above, light below) or, more rarely, concolor. The hind feet are conspicuously fimbriated; similar specialized hairs also are found on the front feet (van Zyll de Jong, 1983). The pelage, although highly variable geographically and seasonally, is generally black or gray frosted dorsally and white tinged with gray or brown ventrally. The chin usually is lighter in color than other body regions (Dalquest, 1948; van Zyll de Jong, 1983)... The feet of S. palustris have a fringe of stiff hairs (fibrillae) located on the outer and inner margins of the front and hind feet and toes; the longest fibrillae (1.25 mm) are found along the outer margins of the hind feet. The large, fimbriated hind feet provide the main thrust for swimming (van Zyll de long, 1983)."
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 |
|---|---|---|---|---|---|---|
| Carolinas, Virginia, Maryland | Webster et al. (1985) | 153 | 68 | 20 | ||
| Colorado | Armstrong et al. (2010) | 140–175 | 63–80 | 18–21 | 13–19 | |
| Great Lakes Region | Kurta (2017) | 138–164 | 63–74 | 19–20 | 10–18 | |
| Minnesota | Hazard (1982) | 136–158 | 62–76 | 18–21 | 7–11 | 11.4–19.1 |
| North Dakota | Seabloom et al. (2020) | 149 | 67 | 19 | 9 | males: 15.4; females: 12.3 |
| Virginia | Linzey (1998) | 135–165 | 60–75 | 9–14 |
Skull
| Sorex palustris skull characters | |
|---|---|
| units in mm | |
| Skull | |
| Condylobasal length: | 19.1–21.7 (Beneski & Stinson, 1987) |
| Postmandibular canal: | Absent |
| Shape: | Rostrum straight or downcurved only slightly; braincase broad and flattened |
| Dental | |
| Upper unicuspids: | 5 |
| Unicuspid notes: | U3<U4 |
| Tines present: | Yes |
| Tine size: | Small |
| Tine position: | Below upper limit of pigment on upper incisors |
| Shape upper incisors: | Diverging |
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Upper incisors of Sorex palustris, scale is 0.5 mm. Borrowed from Nagorsen et al. (2017).
Similar species
Sorex navigator was split from S. palustris in 2014 by Hope et al. Nagorsen et al. (2017) provides the following information for distinguishing S. navigator from S. palustris: "We found no differences in external morphology. Both species had five paired pads on digits 3 and 4. Dorsal and ventral pelage colour and the degree of bicolouring of the tail varied among individuals, but we observed no interspecific differences. Similarly, the bristle fringe of hairs on the hind feet and degree of lateral flattening of the tail was similar in both species. In both species, ventral pelage colour ranged from silvery-grey to brown. Sorex navigator from Vancouver Island differed from other samples in having brown markings on the ventrum. Dorsal pelage colour of S. navigator and S. palustris ranged from brown to black with some individuals of each species showing white tips on dorsal guard hairs. Both taxa had distinctly bicoloured tails with a paler underside... Pigmentation on the anterior face of I1 [upper incisor] and its associated tine was generally darker extending higher on the tooth in S. navigator compared with S. palustris."
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Range of Sorex navigator. -
Range of Sorex palustris. -
Upper incisors of Sorex navigator. Borrowed from Nagorsen et al. (2017). -
Upper incisors of Sorex palustris. Borrowed from Nagorsen et al. (2017).
Taxonomic notes
From Woodman (2018): "Hope et al.’s (2014) investigation of the molecular phylogenetics of North American water shrews revealed three species-level clades among the subspecies formerly united as Sorex palustris: eastern Sorex albibarbis, western cordilleran Sorex navigator, and boreal Sorex palustris (sensu stricto). Nagorsen et al. (2017) demonstrated that parapatric S. navigator and S. palustris can be distinguished morphometrically."
References
Beneski JT, Stinson DW. 1987. Sorex palustris. Mammalian Species (296): 1-6.
Dalquest WW. 1948. Mammals of Washington. Lawrence (KS, USA): University of Kansas publications, Museum of Natural History 2: 1-444.
Ingles LG. 1965. Mammals of the Pacific states: California, Oregon, and Washington. Stanford (CA, USA): Stanford University Press 506 pp.
Johnson DH. 1951. The water shrews of the Labrador Peninsula. Proceedings of the Biological Society of Washington 64: 109-116.
Nagorsen DW, Panter N, Hope AG. 2017. Are the western water shrew (Sorex navigator) and American water shrew (Sorex palustris) morphologically distinct?. Canadian Journal of Zoology 95(10): 727-736.
Richardson J. 1828-04. Short characters of a few quadrupeds procured on Capt. Franklin's late expedition. Zoological Journal 3(12):516-520.
van Zyll de Jong CG. 1983. Handbook of Canadian mammals: marsupials and insectivores. Ottawa (ON, Canada): National Museum of Natural Sciences 1:1-210.
Woodman N. 2018. American Recent Eulipotyphla: Nesophontids, Solenodons, Moles, and Shrews in the New World. Smithsonian Contributions to Zoology. https://doi.org/10.5479/si.1943-6696.650