Mount Lyell shrew (Sorex lyelli) in the Sierra Nevada, California, with comments on alpine records of Sorex.
On 10 August 2005, we found a dead S. lyelli, floating along the shore of the alpine Frog Lake (8,920-[m.sup.2] surface area) in Humphreys Basin, John Muir Wilderness Area, Fresno County, California, 3,630 m elevation (37.2566[degrees]N, 118.6805[degrees]W; NAD 83/WGS 84). It is unlikely that the shrew was transported by a predator to the location where it was found; the specimen had no puncture wound or other evidence that it had been transported.
The specimen was preserved as a whole animal in 95% ethyl alcohol and housed in the Museum of Wildlife and Fish Biology, University of California, Davis (WFB-6512). Determination of species was completed by A. Engilis by comparisons with specimens of S. lyelli deposited at the Museum of Vertebrate Zoology, University of California, Berkeley (MVZ) and using Junge and Hoffmann (1981). It was a female in non-reproductive condition. Measurements were (in mm) : total length, 102; length of tail, 46; length of hind foot, 12; length of ear, 7. Except for length of tail, measurements were consistent with those reported in the literature (tail was 3 mm longer than previously reported; Hall, 1981; Junge and Hoffmann, 1981). However, the length of tail was within the range (37-46 mm) of recently collected specimens housed at the MVZ and examined by the second author. An accurate weight could not be taken as the specimen was found in water and was immediately preserved in alcohol. We did not remove the skull but the diagnostic dental features were easily visible when the lips were parted; the third unicuspid was larger than the fourth and the median surfaces of unicuspid teeth were pigmented. In California, the former characteristic is unique to S. lyelli. No external characteristic reliably separates S. lyelli from other Sierran Sorex.
The collecting locality extends the southern distribution of S. lyelli from Mammoth Lakes (Howell, 1924) by ca. 55 km (Fig. 1). Sorex lyelli had been reported from southeastern Tuolumne County to northeastern Fresno County; thus, encompassing eastern Mariposa and Madera counties, and western Mono County (Ingles, 1947). This is the first record in Fresno County and is the first record of Sorex above 3,500 m in the Sierra Nevada. Prior to this specimen, the elevational range for this species had been 2,000-3,156 m, predominantly in the Canadian and Hudsonian life zones (Grinnell and Storer, 1924; Ingles, 1947; Williams, 1984; Hutterer, 2005). This specimen increases the known elevational range of S. lyelli by nearly 500 m and is the first collected in the Arctic-Alpine life zone. One S. lyelli specimen label at the University of Washington Burke Museum of Natural History and Culture (UWBM-71769) has a recorded elevation of 3,350 m, with no notes on habitat. However, this elevation was recorded erroneously because it was collected at Tioga Pass (3,050 m, a subalpine habitat), Yosemite National Park U. Bradley, pers. comm.). Furthermore, all other species collected on that trip and labeled Tioga Pass had recorded elevations of 3,050 m.
This record indicates that S. lyelli may be more widespread in the southern Sierra Nevada than previously known. The paucity of reports might reflect limited sampling effort above 3,000 m rather than actual rarity. Although trapping efforts have been made on the eastern slope of the Sierra Nevada and in Sequoia and Kings Canyon national parks (MVZ collections database, http://mvzarctos.berkeley.edu/Specimen-Search.cfm), most high-elevation collecting in the region has centered in and around Yosemite National Park, where access to high-elevation habitats is relatively easy. It is possible that the southern range limit of S. lyelli continues beyond that reported here.
Grinnell and Storer (1924:47) described habitat of S. lyelli as "moist situations, near streams, in grass or under willows." This was later expanded to include high-elevation (2,500 m) wetlands, meadows, and sagebrush-steppe communities (the latter is the least frequent habitat association) within the Sweetwater Mountains and the eastern slope of the Sierra Nevada (Howell, 1924; Williams, 1984). Recent surveys in Yosemite National Park indicated that S. lyelli exhibits strong affinities with grassy meadows near fast-flowing water with willow thickets U. L. Patton, pers. comm.). To the list of habitats associated with this species, we add sparsely vegetated alpine meadows mixed with rocks and boulders. Presence of grass seems to be the only feature consistent among specimens captured to date; however, most specimens also were captured near a water source, whether a river, a meadow with wet soils, a lake, or a combination of wetland features.
[FIGURE 1 OMITTED]
Frog Lake is snow-fed with no water-scoured inlets, but with one intermittent outlet composed of a boulder substrate with no riparian vegetation. Vegetation at Frog Lake is limited to herbaceous cover typical of the Arctic-Alpine life zone; there are no trees or shrubs. To quantify habitat surrounding the lake, we recorded percentage cover of each species of plant, bare soil, or exposed rock contained within 12 1-[m.sup.2] quadrats placed at 0, 5, and 10 m from the shoreline at each cardinal direction. Distributions of plants recorded at Frog Lake continue both north and south of Humphreys Basin (Weeden, 1996). Dominant strata of the pooled data from all 12 quadrats were: rock (34.3%), bare soil (19.8%), five species of sedge (13.2% total, including Carex vernacula, C. nigricans, C. heteroneura, C. helleri, and C. breweri), unidentified moss (6.6%), Drummond's rush (Juncus drummondii, 4.3%), short hair reedgrass (Calamagrostis breweri, 3.1%), purple mountain heather (Phyllodoce breweri, 2.9%), bluegrass (Poa stebbinsii, P. cusickii, or both, 2.7%), mountain laurel (Kalmia polifolia, 2.5%), sibbaldia (Sibbaldia procumbens, 2.4%), and alpine pussytoes (Antennaria media, 2.3%). Species with <2% cover included, in order of dominance, spike trisetum (Trisetum spicatum), granite mousetail (Ivesia muirii), alpine willow (Salix arctica), frosted buckwheat (Eriogonum incanum), Sierra beardtongue (Penstemon heterodoxus), heath wood rush (Luzula orestera), pussypaws (Calyptridium umbellatum), rockcress (Arabis platysperma), glaucus willowherb (Epilobium glabenimum), and little elephant heads (Pedicularis attolens).
Occurrences of other species of Sorex at high elevation (>3,000 m) in the Sierra Nevada include S. monticolus, S. vagrans, S. palustres, and S. tenellus. Specimens of S. lyelli, including the type specimen (Merriam, 1902), S. monticolus, S. palustres, and S. tenellus have been collected in headwaters of the Lyell Fork of the Tuolomne River, Yosemite National Park (e.g., MVZ Mamm-22058, 22062, 216156, and 216124). Overlap of species at this and other collection sites indicates that these four species of Sorex coexist. Sorex lyelli and S. vagrans may also coexist as they have both been collected in Humphreys Basin. However, the extent of coexistence or interactions has not been studied.
In the Sierra Nevada, S. monticolus has been recorded to an elevation of 3,400 m (MVZ Mamm-206390), including one record at 3,300 m in Humphreys Basin (MVZ Mamm-77025). Sorex vagrans has been collected in Humphreys Basin at 3,400 m (MVZ Mamm-118573). Sorex palustrs has been collected at 3,350 m in the Sierra Nevada (MVZ Mamm-16299) and at 3,535 m in the White Mountains of California (MVZ Mamm-25844 and 25845). Sorex tenellus has been collected at 3,120 m in the Sierra Nevada (MVZ Mamm-216124 and 217167). In North America, however, S. tenellus holds the highest elevational record for Sorex. It has been documented near the summit of White Mountain Peak, Inyo County, California, 4,267 m (MVZ Mamm-185224 and 185225) and near the White Mountain Research Station Barcroft Laboratory, 3,993 m, (MVZ Mamm-176620). These records support the report of S. tenellus, as described from "scats of a small shrew" (Bole, 1938:245) at 4,300 m on the summit of White Mountain Peak, Inyo County, California. Given this high elevational record for North America, it is surprising that in the Sierra Nevada, S. tenellus has not been documented at >3,120 m. Sorex that occur at high elevations (>3,000 m) elsewhere in North America include S. nanus, S. vagrans, S. cinerus, S. palustres, and S. monticolus (Hoffmann and Taber, 1960; Brown, 1967; Pattie and Verbeek, 1967).
We thank J. L. Patton (University of California, Berkeley), D. A. Kelt, R. E. Cole, J. A. Trochet (University of California, Davis), C. Conroy (University of California, Berkeley), and j. Bradley (University of Washington, Seattle) for comments on the manuscript and assistance in identification of the specimen. Additional information regarding collections of S. lyelli was provided by J. Dines (Natural History Museum of Los Angeles County), K. C. Molina (University of California, Los Angeles), and S. McLaren (Carnegie Museum of Natural History). We thank M. Tognelli for translating the abstract into Spanish and C. T. Liang for Fig. 1. The manuscript was improved by comments from C. L6pez-Gonzalez and two anonymous reviewers. This research was partially funded by the United States Environmental Protection Agency under the Science to Achieve Results, Graduate Fellowship Program (F5F21828 to P. Epanchin), and the University of California Natural Reserve System, Valentine Eastern Sierra Reserve (Graduate Student Grant to P. Epanchin).
Submitted 30 January 2008. Accepted 29 November 2008.
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PETER N. EPANCHIN * AND ANDREW ENGILIS, JR.
Graduate Group in Ecology, Entomology Department, University of California, Davis, CA 95616 (PNE)
Museum of Wildlife and Fish Biology, University of California, Davis, CA 95616 (AE)
Associate Editor was Celia Lopez-Gonzalez.
* Correspondent. firstname.lastname@example.org
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|Author:||Epanchin, Peter N.; Engilis, Andrew, Jr.|
|Date:||Sep 1, 2009|
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