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Sorex nanus

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA MAMMALIA EULIPOTYPHLA SORICIDAE

Scientific Name: Sorex nanus
Species Authority: Merriam, 1895
Common Name(s):
English Dwarf Shrew
Taxonomic Notes: Sorex nanus apparently diverged only recently from S. tenellus and may not yet be a separate species (George 1988). However, George (1988), Jones et al. (1992), and Hutterer (in Wilson and Reeder 2005) listed nanus and tenellus as separate species.

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): NatureServe (Hammerson, G.)
Reviewer(s): Amori, G. (Small Nonvolant Mammal Red List Authority) & Chanson, J. (Global Mammal Assessment Team)
Justification:
Listed as Least Concern because it is very widespread, there are no major threats, and its population is not declining fast enough to qualify for a threatened category.

Geographic Range [top]

Range Description: This species occurs in the United States and is found across central Montana to northwestern Wyoming; southeastern Montana; western South Dakota; the Rocky Mountains from southeastern Wyoming, south across western Colorado and southeastern Utah to south-central New Mexico; in the Kaibab Plateau, San Francisco Peaks, and White Mountains in Arizona (Hoffmann and Owen 1980, MacCracken et al. 1985, Berna 1990, George 1990, Backlund 1995).
Countries:
Native:
United States (Arizona, Colorado, Montana, Nebraska, New Mexico, South Dakota, Utah, Wyoming)
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: There are no population estimates available. It is rarely captured except in pitfall traps; and it is likely to occur in many more locations than currently known. Its population is apparently secure.
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: It is found in various habitats including rocky areas in alpine tundra and partly into subalpine coniferous forest, other types of rocky slopes (e.g., with ponderosa pine, George 1990), sedge marsh, subalpine meadow, dry brushy slopes, arid shortgrass prairie, dry stubble fields, and pinyon-juniper woodland. In some areas the dwarf shrew is sympatric with S. monticolus.

At high elevation, breeding probably begins in late June-early July; and the first litters are produced in late July-early August; and the second litters are born in late August-early September; embryo counts averaged 6.5 for second litters; females breed in their second year. At lower elevations, breeding may begin earlier and litter size and frequency may be greater (Clark and Stromberg 1987). It is an active hunter, and feeds primarily on insects, spiders, and other small invertebrates (worms, molluscs, centipedes, etc.). It may also consume vegetable matter as well as some small vertebrates (salamanders, etc.). It is active throughout the year.
Systems: Terrestrial

Threats [top]

Major Threat(s): There are no known threats to this species.

Conservation Actions [top]

Conservation Actions: It probably occurs in several designated wilderness areas (Absoroka-Beartooth).

Citation: NatureServe (Hammerson, G.) 2008. Sorex nanus. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 21 December 2014.
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