Sorex ornatus
Ornate Shrew
(Sorex ornatus) | |
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Range | |
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Taxonomic classification | |
Order: | Eulipotyphla |
Suborder: | Erinaceota |
Family: | Soricidae |
Subfamily: | Soricinae |
Tribe: | Soricini |
Genus: | Sorex |
Subgenus: | Otisorex |
Species group: | Sorex vagrans group |
Binomial details | |
Sorex ornatus Merriam, 1895 |
Description
From Owen & Hoffman (1983): "Summer coloration is drab brownish dorsally, grading gradually into a paler ventral color, which is more grayish to buffy brown in most populations. Winter coloration is similar, but slightly darker dorsally and lighter ventrally. The tail is indistinctly bicolored. There is a tendency for size to become larger, and ventral fur darker, from north to south. The darkest subspecies is S. o. sinuosus [northern San Pablo Bay, California], which is almost black both dorsally and ventrally in winter pelage, and only slightly browner in summer pelage."
From Jameson & Peeters (2004): "A rather small, dull brown shrew with a fairly bicolored tail. Members of some populations around the north shore of San Pablo are very dark brown."
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 |
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California | Jameson & Peeters (2004) | 89–108 | 32–44 | 11–13 | 6–8 | 3–7 |
California | Owen and Hoffman (1983) | 80–110 (n=116) | 28–46 (n=117) | 9–14 (n=107) | 2.9–8.7 (n=70) | |
California | Woodman (2012) | head and body: 45–67 (n=41) | 34–45 (n=41) | 11–13 (n=41) | 2.4–6.0 (n=34) | |
California (San Bernardino and Los Angeles Cos.) | Woodman (2012) | head and body: 57–65 (n=6) | 40–48 (n=6) | 12–14 (n=6) | ||
rangewide | Wilson & Ruff (editors, 1999) | 80–110 | 28–46 | 2.9–8.7 |
Skull
Sorex ornatus skull characters | |
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units in mm | |
Skull | |
Condylobasal length: | 14.7–17.1 (Owen & Hoffman, 1983); 15.6–17.1 (Álvarez-Castañeda, 2024) |
Postmandibular canal: | Absent |
Shape: | Relatively flat and broad and depressed interorbitally |
Dental | |
Upper unicuspids: | 5 |
Unicuspid notes: | U3<U4 |
Tines present: | Yes |
Tine size: | Medium |
Tine position: | Below upper limit of pigment on upper incisors |
Shape upper incisors: | Diverging |
Dental characters: | Upper toothrow not crowded, with distinct triangular space between postero-medial edge of the fifth unicuspid and antero-medial edge of premolar; tips of upper incisors are more widely separated partly because of tines |
Inner side of lower jaw without postmandibular canal. From Owen and Hoffman (1983): "Sorex ornatus can be distinguished from other species of the subgenus Otisorex by the following combination of characters: 1) upper third unicuspid tooth smaller than fourth; 2) condylobasal length of skull 14.7 to 17.1 mm; 3) medial tine of upper first incisor tooth contained entirely within pigmented area; 4) upper toothrow not crowded, with distinct triangular space between postero-medial edge of the fifth unicuspid and antero-medial edge of premolar... The skull is relatively flat and broad, and depressed interorbitally."
Morphological variation and subspecies
From Woodman (2019): "Molecular analyses by Maldonado et al. (2001, 2004) demonstrated the existence of three genetic clades (northern, central, and southern) whose geographical distributions do not correspond entirely to those of morphologically defined subspecies of S. ornatus. They showed that S. ornatus sinuosus and some northern populations of S. o. californicus are more closely related to S. vagrans and that S. monticola parvidens is more closely related to S. ornatus. The latter point was also demonstrated morphologically by Woodman (2012)."
From Maldonado et al. (2004): "The genetic study by Maldonado et al. (2001) suggested a deep tripartite subdivision of ornate shrew populations. Apparently, those subdivisions corresponded to an ancient fragmentation of ancestral ornate shrew populations. According to Moritz (1994:373), each of the subdivisions identified in the genetic study should be considered an evolutionarily significant unit (ESU): ‘‘a set of populations that has been historically isolated and, accordingly, is likely to have a distinct potential.’’ However, our results indicate that this genetic divergence is not coupled with morphological divergence. In fact, the morphological variability is partitioned in a different way. The 2 subspecies with a wider distribution, S. o. ornatus and S. o. californicus, show a very distinct morphology, and the limit of their distribution does not correspond with the genetic partition. Crandall et al. (2000) suggested a new definition for ESUs considering evolutionary processes. These authors propose that both ecological and genetic exchangeability should be considered to define conservation units. Genetic divergence should not be used solely to define units for management because morphology might indicate other significant patterns of ecological divergence. Our results represent a complex situation. Populations that seem genetically exchangeable might not be exchangeable at the morphological level, and vice versa. Consequently, in addition to the separate management of the different genetic lineages (southern, central, and northern), our results also suggest that the 5 subspecies with restricted distribution analyzed in this study are morphologically divergent, which implies ecological adaptation and therefore should be managed separately. In particular, S. o. lagunae, S. o. salarius and S. o. relictus appear morphologically divergent from S. o. ornatus and S. o. californicus, whereas S. o. sinuosus and salicornicus do not resemble the surrounding subspecies that are in close proximity. Additionally, the 2 subspecies not included in this study, S. o. willetti and S. o. juncensis deserve further study as they are small and fragmented and have a high probability of extinction (Maldonado 1999)."
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.
Crandall KA, Bininda-Emonds OR, Mace GM, Wayne RK. 2000. Considering evolutionary processes in conservation biology. Trends in Ecology & Evolution 15(7): 290-295.
Jameson EW, Peeters HJ. 2004. Mammals of California (No. 66). Berkeley (CA, USA): University of California Press.
Maldonado JE. 1999. Family Soricidae. Mamíferos del Noroeste de México. La Paz (Mexico): Centro de Investigaciones Biológicas del Noroeste, pp.39-52.
Maldonado JE, Hertel F, Vilà C. 2004. Discordant patterns of morphological variation in genetically divergent populations of ornate shrews (Sorex ornatus). Journal of Mammalogy 85(5): 886-896.
Maldonado JE, Vilà C, Wayne RK. 2001. Tripartite genetic subdivisions in the ornate shrew (Sorex ornatus). Molecular Ecology 10(1): 127-147.
Merriam CH. 1895. Synopsis of the American Shrews of the Genus Sorex. North American Fauna 10, 79.
Moritz C. 1994. Defining ‘evolutionarily significant units’ for conservation. Trends in Ecology & Evolution 9(10): 373-375.
Owen JG, Hoffmann RS. 1983. Sorex ornatus. Mammalian Species (212): 1-5.
Wilson DE, Ruff S, editors. 1999. The Smithsonian Book of North American Mammals. Washington D.C. (USA): Smithsonian Institution Scholarly Press.
Woodman N. 2012. Taxonomic status and relationships of Sorex obscurus parvidens, from California. Journal of mammalogy 93(3): 826-838.
Woodman N. 2019. American recent Eulipotyphla: Nesophontids, solenodons, moles, and shrews in the New World. Smithsonian institution scholarly Press.