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Preble's Shrew - Sorex preblei
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State Rank Reason (see State Rank above)
Observations of this species are infrequent resulting in limited data to assess threats. Species may only breed once in its brief life, so is more vulnerable than many small mammal species.
Details on Status Ranking and Review
Preble's Shrew (Sorex preblei ) Conservation Status Review
Range Extent
Score G - 200,000-2,500,000 km squared (about 80,000-1,000,000 square miles)
Comment 301,076 square Kilometers from Natural Heritage Program range maps
Long-term Trend
Score E - Relatively Stable (±25% change)
Comment Although some preferred habitats may have declined since European settlement it is unlikely that the species has declined more than 25% as a result of this habitat loss
Short-term Trend
Score U - Unknown. Short-term trend in population, range, area occupied, and number and condition of occurrences unknown.
Comment Comprehensive structured surveys have not been conducted with enough frequency to assess trend
Threats
Score U - Unknown. The available information is not sufficient to assign degree of threat as above. (Severity, scope, and immediacy are all unknown, or mostly [two of three] unknown or not assessed [null].)
Comment Not enough information exists about this species within Montana to assess threats
Intrinsic Vulnerability
Score B - Moderately Vulnerable. Species exhibits moderate age of maturity, frequency of reproduction, and/or fecundity such that populations generally tend to recover from decreases in abundance over a period of several years (on the order of 5-20 years or 2-5 generations); or species has moderate dispersal capability such that extirpated populations generally become reestablished through natural recolonization (unaided by humans).
Comment Species is short lived and may only prduce 1-2 litters within its lifetime, size may limit long distance dispersal
Environmental Specificity
Score C - Moderate. Generalist. Broad-scale or diverse (general) habitat(s) or other abiotic and/or biotic factors are used or required by the species but some key requirements are scarce in the generalized range of the species within the area of interest.
Comment Collected from diverse habitat types, but may be limited to specific features within these habitats
Raw Conservation Status Score
Score
3.5 + 0 (geographic distribution) + 0 (environmental specificity) + 0 (long-term trend) + -0.25 (intrinsic vulnerability) = 3.25
General Description
Like other members of the genus Sorex , the snout is long and pointed, and the eyes are small. The dorsal pelage is dark brown to dark gray, and the ventral pelage is silvery-gray. The tail is bicolored, olive-brown above and hazel-brown below. The skull has 32 teeth (dental formula: I 3/1, C 1/1, P 3/1, M 3/3); the 5 upper teeth with single cusps that are present posterior to the first incisor are termed the unicuspids (U), and include 2 incisors, 1 canine, and 2 premolars. The tine on the medial edge of the first incisor is long, acutely pointed, and set within the pigmented area; U3 is as large or larger than U4. Ranges of external measurements (in millimeters) are: total length 77 to 95, tail length 28 to 38, hind foot length 7 to 11, ear length 8 to 11, weight 2.1 to 4.1 grams (Cornely et al. 1992, Verts and Carraway 1998). Published cranial measurements (in millimeters) are: condylobasal length 13.8 to 15.1, palatal length 5.4 to 5.8, cranial breadth 7.0 to 7.2, interorbital breadth 2.9 to 3.1, maxillary breadth 3.8 to 4.2, dentary length 5.6 to 6.7, length of mandibular tooth row (C1-M3) 3.8 to 4.2.
Diagnostic Characteristics
Preble's Shrew is small, even for a shrew. Other than its small body size, Preble's Shrew is diagnosed by cranial characteristics. A combination of a medial tine on I1 that is present within the zone of pigmentation, U3 as large or larger than U4, condylobasal length usually less than 15.1 millimeters, palatal length less than 5.8 millimeters, length of dentary less than 6.5 millimeters, length of mandibular tooth row (C1-M3) usually less than 4.1 millimeters, and height of coronoid process less than 3.3 millimeters (Junge and Hoffmann 1981, Carraway 1995).
Species Range
Montana Range
Range Descriptions
Native
Western Hemisphere Range
Observations in Montana Natural Heritage Program Database
Number of Observations: 57
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
Relative Density
Recency
(Observations spanning multiple months or years are excluded from time charts)
Migration
No information is available on movements in Montana, but based upon information from other locations, the species is considered non-migratory; apparently only local movements are made.
Habitat
Most Preble's Shrews in Montana have been captured in sagebrush-grassland habitats (Hoffmann et al. 1969, Foresman 2012, Hendricks and Roedel 2002), sometimes in openings surrounded by subalpine coniferous forest. They have been taken in Beaverhead County in stabilized sandhills habitat of about 40 to 60% vegetation cover, dominated by grasses (Stipa comata , Festuca idahoensis , Agropyron dasystachyum ) and shrubs (Artemisia tridentata , A. tripartita , Chrysothamnus nauseosus , C. viscidiflorus , and Tetradymia canescens ), with isolated dense patches of Opuntia fragilis present (Hendricks and Roedel 2002). Preble's Shrew was also present at two other grazed sites (in Beaverhead and Powell counties) dominated by medium-stature (0.5 to 1.5 meters tall) sagebrush; at both sites, sagebrush cover was about 25% (Paul Hendricks, unpublished data).Artemisia tridentata , Purshia tridentata , and Amelanchier utahensis more than 30 centimeters tall surrounded by large expanses of Artemisia less than 30 centimeters tall (Kirkland et al. 1997). In southern British Columbia, Preble's Shrews were captured in lightly to moderately grazed grassland patches surrounded by scattered stands of Douglas-fir (Pseudotsuga menziesii ) or ponderosa pine. Big sagebrush, common snowberry (Symphoricarpos albus ), or antelope bitterbush (Purshia tridentata ) about 1 to 2 meters in height formed dense shrub cover of 30 to 80% (Nagorsen et al. 2001); cheatgrass (Bromus tectorum ) was sometimes dominant, and the nearest standing water to trap sites was 350 to 2300 meters distant.
Ecological Systems Associated with this Species
Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (common or occasional) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2012, Adams 2003, and Werner et al. 2004);
Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of "observations versus availability of habitat".
Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were listed as associated with an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not listed as associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system,
even if point observations were associated with that system.
Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignment of common versus occasional association.
If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.
Suggested Uses and Limitations
Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.
These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at:
mtnhp.org/requests ) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.
Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).
Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species' known geographic range.
Literature Cited
Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
Foresman, K.R. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.
Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998. Montana atlas of terrestrial vertebrates. Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT. 1302 p.
Hutto, R.L. and J.S. Young. 1999. Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32. 72 p.
Maxell, B.A. 2000. Management of Montana's amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species. Report to U.S. Forest Service Region 1. Missoula, MT: Wildlife Biology Program, University of Montana. 161 p.
Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath. 2004. Amphibians and reptiles of Montana. Missoula, MT: Mountain Press Publishing Company. 262 p.
Commonly Associated with these Ecological SystemsForest and Woodland Systems
Grassland Systems
Human Land Use
Shrubland, Steppe and Savanna Systems
Sparse and Barren Systems
Wetland and Riparian Systems
Occasionally Associated with these Ecological SystemsRecently Disturbed or Modified
Food Habits
The diet of Preble's Shrew has not been described or the subject of study, but it probably resembles other cinereus-group shrews, feeding on insects and other small invertebrates (worms, molluscs, centipedes, etc.). Its relatively low bite force suggests that it feeds on soft-bodied prey (Cornely et al. 1992, Verts and Carraway 1998). The diet in Montana has not been reported or studied.
Ecology
Little is known about this shrew, but it is probably active all year. It has been captured in spring and late summer in southwestern Wyoming (Kirkland et al. 1997), in summer and during fall to spring in British Columbia (Nagorsen et al. 2001), summer and fall in Nevada (Ports and George 1990), and mid-winter in Utah (Tomasi and Hoffmann 1984). Collection records from Montana range from mid-February to early November. Sorex cinereus , S. haydeni , S. merriami , S. monticolus , S. nanus , and S. vagrans (Ports and George 1990, Cornely et al. 1992, Kirkland and Findley 1996, Kirkland et al. 1997, Nagorsen et al. 2001). Preble's Shrew has been collected in Montana in close association with Sorex cinereus , and S. monticolus (Hendricks and Roedel 2002).
Reproductive Characteristics
The reproductive biology in Montana has not been studied, and in general, the reproductive biology of Preble's Shrew is largely unknown (Cornely et al. 1992). In a sample of 26 specimens from southeastern Oregon collected in June and July, five adult females contained developing embryos: two with 3 embryos, two with 5, and one with 6; mean = 4.4 embryos (Carraway and Verts 1999); all had elongated nipples and extensive mammary tissue suggesting they had produced at least one litter earlier. Four juvenile females exhibited no evidence of reproductive activity. For 16 males, testis size in 15 individuals was either less than 2.0 cubic millimeters (nonreproductive, captured in the year of birth) or more than 16.0 cubic millimeters (reproductive, from older cohorts); one male with intermediate testis size had little wear on I1, indicating it may have just reached sexual maturity. These data suggest that at least two litters were produced before the June and July pregnancies.
Management
No management measures have been enacted for Preble's Shrew in Montana. However, alteration or removal of sagebrush through fire, herbicides, or mechanical methods, may impact local populations (Hendricks and Roedel 2001). Measures taken to protect a diversity of size and cover classes of sagebrush will likely contribute to the conservation of Preble's Shrew. Surveys for Preble's Shrews can provide the basis for development of conservation protocols by determining its full distribution in Montana, the array of habitats in which it occurs, its relative abundance in different habitats, and, if properly designed, an idea of how different habitat disturbances affect this rare shrew.
Stewardship Responsibility
References
Literature Cited AboveLegend: Sorex preblei . Northwestern Naturalist 80:115-116.Sorex preblei . Mammalian Species 416: 1-3.Sorex ) of the United States and Canada, with notes on middle American Sorex . Occasional Papers of the Museum of Natural History, the University of Kansas 94: 1-48.Sorex preblei ) in New Mexico. Southwestern Naturalist 41:320-322.Sorex preblei from the Black Canyon, first record from Colorado. Southwestern Naturalist 37: 318-319.Sorex merriami , and Preble's shrew, Sorex preblei : two new mammals for Canada. Canadian Field-Naturalist 115:1-8.Sorex preblei in the northern Great Basin. Great Basin Naturalist 50: 93-95.Sorex preblei in Utah and Wyoming. Journal of Mammalogy 65: 708.Sorex ) from California. Journal of Mammalogy 65(2):325-328.
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