Banisteria, Number 14, 1999 © 1999 by the Virginia Natural History Society Additional Records of the Rock Vole, Microtus chrotorrhinus (Miller) (Mammalia: Rodentia: Muridae), in Virginia. John L. Orrock Department of Biology, Virginia Commonwealth University, Richmond, Virginia 23284-2012 Elizabeth K. Harper Department of Fisheries and Wildlife, University of Minnesota, St. Paul, Minnesota 55108 John F. Pagels Department of Biology, Virginia Commonwealth University, Richmond, Virginia 23284-2012 William J. McShea Conservation and Research Center, Smithsonian Institution, 1500 Remount Road, Front Royal, Virginia 22630 The southern Appalachian mountains support a rich small mammal study of 353 sampling sites within the small mammal fauna, with representatives that are George Washington and Jefferson National Forests. An typical of boreal climes often existing in sympatry with effort was made to sample all habitat types present in species associated with southern regions (Guilday, the study area according to their abundance in the 1971). The rock vole, Microtus chrotorrhinus, is a landscape, e.g., if xeric oak habitats constituted 50% of boreal rodent whose geographic distribution extends the entire study region, then 50% of the sampling sites from eastern Canada south along the Appalachians to were in xeric oak habitat. At each site, small mammals North Carolina and Tennessee (Kirkland & Jannett, were sampled using eight Sherman live traps (8 x 9 x 23 1982). Microtus chrotorrhinus typically inhabits moist, cm) and one Tomahawk live trap (21 x 21 x 62 cm). A rocky habitats within this region, although clearcuts and pitfall array consisting of three 0.5 1 pitfalls connected disturbed habitats may also be utilized. Southern to a central 0.5 1 pitfall with a 0.3 m high drift fence of populations are considered disjunct (Kirkland & aluminum screening was also installed within each site Jannett, 1982), and may be adversely affected by (Type IB of Handley & Kalko, 1993). Live traps were natural and anthropogenic habitat fragmentation and baited with rolled oats scented with peanut butter or destruction (Handley & Gordon, 1980; Pagels, 1990). peanut oil, and pitfalls were filled with 5 cm of water The relatively low reproductive output of M. during sampling. There were 69 trapnights (TN) of chrotorrhinus (Handley, 1980), which also tends to effort at the Highland County site from 28 May to 1 decrease in southern areas (Kirkland & Jannett, 1982), June 1997. The Bath county site was live-trapped for may also contribute to smaller populations with 69 TN followed by 65 TN with Museum Special traps increased sensitivity to perturbation and local in early summer 1996, and was live-trapped again for extinction. The rock vole, listed as state endangered 69 TN in early summer 1997. The increased effort at (Handley & Pagels, 1991), was previously known in the Bath county site resulted from its inclusion in 30 Virginia from only a single locality in Bath County at an sites that were used to examine the efficacy of our elevation of 1036 m (Pagels, 1990). Here we report an trapping protocol and seasonal fluctuations in small additional record for Bath County and a new record mammal abundance. Specimens of M. chroto-rrhinus from Highland County. were found dead in Sherman live traps and were Voles were collected as part of a larger, ongoing deposited in the Virginia Commonwealth University ORROCK ET. AL.; ROCK VOLE RECORDS 37 Mammal Collection (VCU # 12378 and 14034, Bath smoky shrew (Sorex fumeus) (1), and the pygmy shrew County specimens; VCU # 14031 and 14032, Highland (Sorex hoyi) (1). Small mammals captured at the County specimens). Highland County site were P. maniculatus (6), S. Two individuals of Microtus chrotorrhinus were fumeus (6), B. brevicauda (2), C. gapperi (2), the captured near the upper reservoir of the Bath County woodland jumping mouse (Napaeozapus ins ignis) (2), Hydroelectric Plant at approximately 1,021 m elevation. S. cinereus (1), and P. leucopus (1). These species, Two others were taken at a site in Highland County in especially C. gapperi, have been found in sympatry Kent Simmons Hollow at an elevation of 976 m. All with Microtus chrotorrhinus (Martin, 1971; Timm et captured rock voles were adult females with visible al., 1977; Kirkland & Jannett, 1982; Pagels, 1990). mammae. The new records for Bath and Highland The occurrence of rock voles at only two of 353 counties are 1.4 km north and 3.9 km northeast, sampling sites supports the contention of other respectively, of the original Bath County site (Pagels, researchers (Kirkland, 1977; Pagels, 1990; Handley & 1990). Both sites were in riparian habitats with steep Pagels, 1991) that Microtus chrotorrhinus populations slopes (28u at Bath County site, 31° at Highland County in the area exist in relative isolation. The relatively site). Sites were characterized by abundant vegetation, narrow niche breadth of M. chrotorrhinus may explain moss, talus- and rock-laden slopes typical of M. this distribution to some extent (Clough, 1987), chrotorrhinus habitat (Kirkland & Jannett, 1982). Rock although the true nature of the ecological restriction of or talus at the sites ranged in size from < 0.2 m to > 1 this species is not fully understood (Kirkland & Jannett, m, and woody debris was abundant at each site. 1982). The capture of only two individuals during 203 Herbaceous growth was prevalent at both sites and TN of effort at the Bath county site suggests that low consisted primarily of stinging nettle (Urtica dioica) abundance was common even in suitable habitat in the and jewelweed (Impatiens spp.). study area, in concurrence with the findings of French Woody tree species present at the sites were typical & Crowell (1985) and Guilday (1971). Genetic studies of rock vole habitat as found in the region (Kirkland, suggest that the range of M. chrotorrhinus may not be 1977; Pagels, 1990). Canopy tree species with diameter so fragmented in more northern regions (Kilpatrick & at breast height (dbh) > 10 cm in decreasing abundance Crowell, 1985). However, if genetic exchange occurs at the Bath county site were American basswood (Tilia among populations in the study region, americana), yellow birch (Betula alleghaniensis), and a immigration-enhanced heterozygosity (Kilpatrick & single standing dead tree (snag). Mean dbh of canopy Crowell, 1985) may be offset by inbreeding and trees was 37.8 ± 4.7 cm (n = 10). Subcanopy and relatively low reproductive output (Handley & Gordon, shrub species in decreasing abundance at the site were 1980). witch hazel (Hamamelis virginiana), sugar maple (Acer Whether the distribution of Microtus chrotorrhinus saccharum), mountain maple (Acer spicatum), in the study area is limited by suitable habitat is honeysuckle (Lonicera spp.), basswood, and white ash unknown. Although we did not find this species at (Fraxinus americana). Canopy tree species at the some sites in apparently suitable habitat, this must be Highland County site consisted of basswood, snags, interpreted with caution. Because our sampling slippery elm (Ulmus rubra), striped maple (Acer protocol examined habitats in relation to their pensylvanicum), white ash, and cucumber magnolia abundance, relatively few sites suitable for M. (Magnolia acuminata). Subcanopy and shrub species at chrotorrhinus were sampled due to the rarity of such the site were mountain maple, honeysuckle, mountain biotopes in the southern Appalachian landscape. As laurel (Kalmia latifolia), hornbeam (Ostrya virginiana), such, the presence of optimal habitat may be of concern sugar maple, and hickory (Carya spp). Mean dbh of for the conservation of this species, but the ability of the canopy trees was 20.7 ± 2.4 cm (n = 17). Tree rock vole to successfully colonize other suitable habitats communities at both sites were > 120 years old (U.S. must also be considered. The presence of presumably Forest Service Continuous Inventory of Stand Condition viable populations of M. chrotorrhinus in West Virginia data). (Kirkland, 1977) suggests that source populations exist Other small mammals captured at the Bath County for recolonization of suitable habitat in the study region site were the southern red-backed vole (Clethrionomys (Pagels, 1990). Proximity to these populations gapperi) (19), the cloudland deer mouse (Peromyscus (approximately 33 km) may explain the presence of M. maniculatus) (6), the eastern chipmunk (Tamias chrotorrhinus at these new sites and its absence at other striatus) (4), the northern short-tailed shrew (Blarina apparently suitable habitats that are more distant from brevicauda) (2), the masked shrew (Sorex cinereus) (2), potential source populations. The highly managed the white-footed mouse (Peromyscus leucopus) (1), the landscape of the southern Appalachians may contain 38 BANISTERIA NO. 14, 1999 few suitable dispersal corridors and thus movement of Guilday, J.E. 1971. The Pleistocene history of the M. chrotorrhinus into potential habitats may be Appalachian mammal fauna. Pp. 233-262 In P. C. Holt restricted (Anderson & Danielson, 1997; Rosenberg et (Editor), The Distributional History of the Biota of the al., 1997). Additionally, the presence of adequate Southern Appalachian Mountains, Part III: Vertebrates. corridors may provide stability to apparently small Virginia Polytechnic Institute & State University populations that are likely to become locally extinct by Research Division Monograph 4, Blacksburg, VA. random processes alone (Rosenberg et al., 1997). Maintenance of viable, genetically diverse populations Handley, C.O. Jr., & L. K. Gordon. 1980. Rock vole. of Microtus chrotorrhinus in the study area is Microtus chrotorrhinus carolinensis Komarek. Pp. contingent upon management decisions that minimize 574-577 In D.W. Linzey (Editor), Threatened and alteration of existing habitat and promote suitable Endangered Plants and Animals of Virginia. Center of dispersal corridors within the landscape. Environmental Studies, Virginia Polytechnic Institute & State University, Blacksburg, VA. ACKNOWLEDGMENTS Handley, C.O. Jr., & J.F. Pagels. 1991. Rock vole. Pp. Collection of specimens obtained during the 589-591 In K. Terwilliger (Coordinator), Virginia's Allegheny Mountain Project was supported by funds Endangered Species. McDonald & Woodward from the U.S.D.A. Forest Service to Virginia Publishing Co., Blacksburg, VA. Commonwealth University and the Conservation and Research Center (CRC) of the Smithsonian Institution. Handley, C.O. Jr., & E.K.V. Kalko. 1993. A short We thank the many field biologists and Earthwatch history of pitfall trapping in America, with a review of volunteers from the CRC and VCU that aided in the methods currently used for small mammals. Virginia collection effort. Sarah Bell and other personnel at the Journal of Science 44: 19-26. Bath County Pumped Storage Hydroelectric Facility kindly provided site access and climatological data. We Kilpatrick, C.W., & K.L. Crowell. 1985. Genic thank the staff at the Warm Springs Ranger Station in variation of the rock vole, Microtus chrotorrhinus. Warm Springs, Virginia, especially District Ranger Teri Journal of Mammalogy 66: 94-101. Rami, and biologists Terry Flaherty and Steve Tanguay. Charlene Couch prepared specimens and performed the Kirkland, G.L., Jr. 1977. The rock vole, Microtus necropsy. The study benefited from the cooperation, chrotorrhinus (Miller)(Mammalia: Rodentia) in West advice, and direction of residents around the study area Virginia. Annals of the Carnegie Museum of Natural in Mountain Grove, Virginia and Frost, West Virginia. History 46: 45-53. LITERATURE CITED Kirkland, G.L., Jr., & F.J. Jannett, Jr. 1982. Microtus Anderson, G.S., & B.J. Danielson. 1997. The effects of chrotorrhinus. 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