Originally thought to be restricted to the Canadian boreal coniferous forest, Microtus chrotorrhinus has also been found in the mixed forest of the transition zone in New York, West Virginia, Cape Breton Island (Nova Scotia) and Minnesota (Christian 1985). Currently the two subspecies of M. chrotorrhinus are found throughout the northern hardwood forests where appropriate microhabitat components are present (Kirkland et al. 1979) and the upper elevations of the northern Appalachians (Banfield 1974).

Biogeographic Regions: nearctic (Native )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (250-20,000 square km (about 100-8000 square miles)) Labrador west to Ontario and northeastern Minnesota, southward at higher elevations through the Gaspe Peninsula, New Brunswick, New England, New York, and northeastern Pennsylvania, and disjunctly in the southern Appalachians to Virginia, western North Carolina, and eastern Tennessee (Handley 1991). A 400-km disjunction separates populations in northeastern Pennsylvania from those in northern West Virginia (Kirtland and Jannett 1982; Kirtland, pers. comm., 1994). Subspecies Carolinensis: fairly common in the Great Smoky Mountains; most abundant above 1200 m, but as low as 800 m. An isolated population in eastern West Virginia (where common, and occurring as low as 600 m), western Maryland, and western Virginia has relatively small teeth but otherwise most closely resembles subspecies Carolinensis (Handley 1991). Hall's (1977) map shows Carolinensis occupying southern Appalachia from Tennessee and North Carolina north through West Virginia, possibly into western Maryland and southern Pennsylvania, but Martin (1971) restricted it to North Carolina and Tennessee. Subspecies RAVUS occurs in eastern Labrador. Adams (1987) stated that the southern rock vole occurs throughout the higher Appalachians from Randolph and Pendleton counties in West Virginia (McKeever 1951) southward to Swain County, North Carolina, and Sevier County, Tennessee (Hamilton and Whitaker 1979). Subspecies CHROTORRHINUS occupies the extensive range between RAVUS and Carolinensis.

Microtus chrotorrhinus is one of the rarer North American small mammals. It is a medium sized vole, 140 to 185 mm long, weighing 30 to 48 grams (Kirkland et al. 1982). Rock voles are ventrally grayish brown back and dull to silvery gray with an orange face and rich yellow around the nose spreading backwards to include the ears. The winter coat is longer and glossier (Forsyth 1985). The ears are moderately large, tail is rather sparsely haired and of average length for a vole, 42 to 64 mm, also slightly paler below (Banfield 1974). Sexual dimorphism in this species is minute; males are usually slightly larger than females (Kirkland et al. 1982). A key identifying characteristic for this species is found in its dentition. The dental formula is 1/1, 0/0, 0/0, 3/3 = 16 teeth (Forsyth 1985). The third molar is characterized by five closed triangles (Banfield 1974).

Range mass: 30 to 48 g.

Length: 16 cm

Weight: 36 grams

The rock vole closely resembles the common meadow vole (Microtus pennsylvanicus), but the former has a conspicuously yellow-orange snout and five enamel triangles instead of three on the third upper molar.

• Terrestrial

Rock voles are specialized in their habitat selection and occupy cool, moist, rocky, northern hardwoods and mixed deciduous-coniferous forests dominated by Yellow Birch (Betula lutea), Sugar Maple (Acer saccharum), and American Beech (Fagus grandifolia). As their name indicates, rock voles live among mossy rocks and boulders in forests with moderately open canopies and a rich herbaceous under story. Rock voles are usually found in areas of small clearings or wind-downed trees where exposed boulders and crevices are visible (Christian et al. 1985). Water, either in the form of surface or subsurface streams, is another key habitat component (Kirkland et al. 1979).

The known predators of rock voles include hawks, owls, gulls, snakes, and other small carnivores (Forsyth 1985).

Terrestrial Biomes: forest

Comments: Cool, damp, coniferous and mixed forests at higher elevations in the Appalachians; mossy rocky areas throughout Canada. Optimal habitat: ferns/mossy debris near flowing water in coniferous forests. Also occupies deciduous forest/spruce clearcuts (mainly recent cuts), forest ecotones, grassy balds near forest, and sterile-looking rocky road fills. Occupies shallow burrows and runways. Nests probably are placed under logs or in similar protected sites. They are made of moss with a lining of grass and have multiple entrance tunnels. "Sphagnum moss is frequently pulled off in clumps where rock voles are found...," presumably for use in nest building (Martin 1971).

Although rock voles have been trapped in a variety of habitats, they typically occur in moist talus or among mossy rocks and logs in spruce and northern hardwood forests. Overstory is most commonly red spruce (Picea rubens), often with birches (BETULA spp.), poplar and aspen (POPULUS spp.), other northern hardwoods, or fir (Abies balsamea). In the Appalachians, the forest is often birch, various other hardwoods and hemlock (Tsuga canadensis). Ground cover characteristically includes an abundance of mosses, ferns, and northern herbs and subshrubs such as bunchberry (Cornus canadensis), blueberry (VACCINIUM spp.), Canada mayflower (Maianthemum canadense), blue-bead lily (Clintonia borealis), star-flower (Trientalis borealis), and Labrador tea (Ledum groenlandicum). Other habitats include unvegetated talus, grass balds, recent clearcuts, and roadfills, but these sites have dense vegetation nearby. There is usually a stream or other surface water in the immediate vicinity, but Martin (1971) speculated that fog intercepted by rocks and vegetation may be an important source of drinking water in some localities, such as coastal Labrador. Moist situations are clearly favored, as are higher elevations.

Martin (1971) thought that records from atypical habitat may represent expansion of populations under favorable conditions. These might also be dispersing individuals.

Fecal pellets are deposited in special latrine areas. Martin (1971) found a latrine, 50 cm in diameter and 24 cm deep, in a rock crevice.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

The primary food source of rock voles is Bunchberry (Cornus canadensis). The presence of this plant is thought to be indicative of the presence of M. chrotorrhius (Hamilton 1943). However, rock vole's diet also includes Clinton's Lily (Clintonia borealis), Canada mayflower (Maianthermum canadensis), False miterwort (Tiarella cordifolia), Wood Sorrel (Oxalis montana), mosses, and ferns (Banfield 1974, Christian et al. 1985). Rock voles cut herbaceous vegetation and pull the cuttings down into the subterranean galleries where they apparently spend much of their lives (Kirkland et al. 1979). Cut stems and leaves of forbs and other green plants can reveal the presence of M. chrotorrhinus.

Comments: Diet includes foliage, stems, and fruits of herbaceous plants (forbs more often than grasses and sedges), and fungi. Martin (1971) found bunchberry (Cornus canadensis) fruits and plants to be a preferred food. He also recovered wavy-leafed thread moss (Atrichum undulatum) from the mouth and stomach of a snap-trapped animal in New York, and he noted that a Quebec specimen tag recorded unidentified moss as stomach contents. Komarek and Komarek (1938) found blackberry (Rubus spp.) seeds in the stomach of a Great Smoky Mountains specimen, and Timm et al. (1977) noted that a captive subadult ate insects. The following plants were recorded by Martin (1971) from various collectors' specimen tags and field notes as cuttings in rock vole runs: false miterwort or foamflower (Tiarella cordifolia), violet (Viola incognita), Canada mayflower (Maianthemum canadense), alpine goldenrod (Solidago cutleri), unidentified goldenrod, bunchberry, alder (Alnus sp.) avens (Geum sp.), and spinulose wood fern (Dryopteris spinulosa). Like other voles, the rock vole cuts these plants and stores the pieces in subterranean caches. Mushrooms and lepidoptera larvae have also been mentioned as foods (Merritt 1987). Stomachs of three specimens from the Great Smoky Mountains contained 99.7% plant material and 0.3% hypogeous fungus (Endogone sp.) (Handley and Gordon 1979).

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

10,000 to >1,000,000 individuals

Comments: "Common" in the northern range, much less abundant in the southern and eastern range. However, according to Banfield (1974), "the rock vole is one of the rarer Canadian small mammals...occurs in small isolated colonies throughout its range...dense populations of this species have never been found." Jaques Prescott (Quebec Zoo, tel. 418-622- 0313) stated this is "one of the rarest and least known of the small mammals in Quebec" (Guy Jolicoeur, pers. comm.). Christopher Fichtel of Vermont (pers. comm.), Charles Bier of Pennsylvania (pers. comm.), and Harry LeGrand, Jr., of North Carolina (pers. comm.) reported that the rock vole may be more common than records indicate.

Small isolated colonies seem to be the rule (Banfield 1974). Home ranges probably are less than an acre.

Frequent associates include the red-backed vole (Clethrionomys gapperi), deer mouse (Peromyscus maniculatus), and often with masked, smoky, and short-tailed shrews (Sorex cinereus, S. FUMEUS, and Blarina brevicauda) (Martin 1971, Kirkland 1977, Timm et al. 1977). Martin (1977) found no evidence of rivalry between red-backed and rock voles, but thought that the latter may competitively exclude the meadow vole (Microtus pennsylvanicus) from prime rock vole habitat where the two occur together. Deer may be an important competitor in some areas (see GTHREATCOM).

Rock vole remains have been found in the stomachs of a bobcat (Lynx rufus) in the Great Smoky Mountains National Park (Linzey and Linzey 1968) and three rattlesnakes (Crotalus horridus) and a copperhead (Agkistrodon contortrix) from the same area. Other predators doubtless include other snakes, weasels, foxes, and short-tailed shrews. Merritt (1987) stated that "predation by avian predators is probably minimized because of inaccessibility of its foraging zone."

Common parasites include fleas, mites, ticks, botflies (Diptera:Cuterebridae), tapeworms and roundworms. Six specimens collected in New York in 1947 "exhibited severe damage to the ears by an unidentified fungus" (Martin 1972).

Comments: Active day or night (Handley 1991). Also reported as primarily diurnal, with greatest feeding activity taking place in the morning (Martin 1971). Does not hibernate; active all year.

M. chrotorrhinus breeds from early spring until late fall (Hamilton 1943). The gestation period is unknown but suspected to last 19 to 21 days (Kirkland 1982, Forsyth 1985). The litter size is 2 to 5 young with two or more litters per year, depending on female size (Kirkland 1982). The age of maturity for rock voles is probably 25 to 45 days; the lifespan is probably less than one year (Forsyth 1985).

Breeding season is from March to mid-October. Gestation lasts 19-21 days. Up to 3 litters of 1-7 (typically 3-4) young are reared each year. Birthing peaks in late spring-early summer. Spring progeny breed in their first summer (Timm et al. 1977). Males are sexually mature at 15 cm body length and 30 g. Females reach sexual maturity at about 13 cm body length and 30 g. See Martin (1971), Kirkland (1977), and DeGraaf and Rudis (1986).

Recent studies have found that rock voles occupy a much wider range than initially expected (Christian et al. 1985, Kirkland 1982). However, not much is known about their population densities (Christian et al. 1985). Some studies indicate population constancy (Jannett 1990) and therefore, M. chrotorrhinus is not considered threatened. Rock voles are found in small, localized populations occurring in fairly restricted, patchy habitat. Further research is needed to understand the implications of this pattern for conservation (Christian et al. 1985).

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

Canada

Rounded National Status Rank: N4 - Apparently Secure

United States

Rounded National Status Rank: N4 - Apparently Secure

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: Occurs as scattered populations in patches of suitable habitat in southeastern Canada, the adjacent northeastern U.S., and southward through the Appalachian Mountains; still relatively common in many areas, but abundance varies across range; rocky habitat generally is not suitable for human use or development.

Global Short Term Trend: Unknown

Comments: Too little is known to accurately assess current population trends. Historically, a long-term decline appears to have occurred, related to land use and/or climate change (Christian, pers. comm., 1994).

Degree of Threat: C : Not very threatened throughout its range, communities often provide natural resources that when exploited alter the composition and structure over the short-term, or communities are self-protecting because they are unsuitable for other uses

Comments: The principal current threat probably is destruction of habitat, but this may be less of a problem than for many other rare species; the preferred habitat, high elevation talus slopes (in the eastern portions of the range) and other rocky areas, is generally unsuitable for development. Abundant rocks also provide a very uniform subterranean environment that is not highly vulnerable to disturbance. However, Fichtel (pers. comm., 1992), in discussing threats to the habitat of the long-tailed shrew (Sorex dispar) in Vermont, suggested that ski area development may destroy habitats of this sort. Logging does not appear to have any immediate adverse impact (Kirtland 1977, Christian and Daniels 1985). In fact, at three West Virginia sites, rock voles were more than twice as abundant on recent clearcuts as on adjacent uncut stands (Kirkland 1977). The rock vole is a habitat specialist and occurs in isolated colonies throughout its range (Banfield 1974, Kirtland and Jannett 1982, Majumdar et al. 1986, Kirkland and Krim 1990). "Habitat specialization in a species frequently is associated with a limited geographical distribution and small populations. Species having such characteristics ... may be subject to extinction due to stochastic events" (Kirtland 1986 or Majumdar et al. 1986). Chemical and heavy metal pollution may have less effect on this primarily vegetarian species than on predators in the same habitat. Brooks and Healy (1988), working in West Virginia and Massachusetts hardwood forests, concluded that both intermediate thinning and clearcutting have minimal or ephemeral effects on small mammal communities, but that "long-term, high deer populations may permanently alter habitat structure to the extent that changes occur in small mammal community composition."

Preserve Selection and Design Considerations: Aside from the need for extensive, favorable habitat conditions, no specific suggestions can be made.

Management Requirements: Maintenance of the forest on appropriate sites is the primary management consideration. Water sources must also be preserved--the rock vole has a high water requirement.

Usual logging practices seem not to harm this species; insofar as they stimulate the growth of groundcover, they are probably beneficial, increasing food supply. Populations may increase following clearcuts (Kirkland 1977), but this finding must be interpreted with caution in view of the fact that rock voles prefer forested habitat.

Martin (1971) reported that populations of the subspecies M. C. CHROTORRHINUS "vary widely, both within clines and independently," and that "gene interchange is restricted, even among closely adjacent populations." It is advisable therefore to be sure that rock voles are indeed extirpated from a site before reintroduction from even a nearby population.

The difficulty of maintaining M. CHROTORRHINUS in the laboratory was mentioned by Martin (1971) without elaboration. He reported that he kept one for 108 days.

Management Research Needs: Little is known about basic ecology and population dynamics. Timm et al. (1977) recommended research to identify how rock voles compete successfully with other microtine rodents, especially red-backed voles (Clethrionomys gapperi), which appear to inhabit similiar habitats. Kirtland (pers. comm., 1994) added that rock voles and red-backed voles are found in the same habitat and are often taken in the same traps. Rock voles also appear to compete with meadow voles (Microtus pennsylvanicus) (Christian, pers. comm., 1994; Hight, pers. comm., 1994). The minimum population size needed to maintain viability in a fragmented habitat should be examined. Christian and Daniels (1985) stated that further research is needed to determine the impact of forest management practices and natural disturbance on habitat quality for this species.

Global Protection: Few to several (1-12) occurrences appropriately protected and managed

Comments: Most of the North Carolina population is within Great Smoky Mountains National Park. Many other populations are in national forests, parks, or other public lands affording some protection. Many populations are somewhat protected by being in remote areas not currently impacted by human activities.

Needs: The primary need is to protect the habitat of the rock vole from gross disturbance.

No information available

No information available.

Stewardship Overview: The rock vole is a boreal species and a Pleistocene relict in Appalachia. It requires cool, moist, forested, rocky habitat with a reliable source of water. Higher elevations are preferred. Very little is known of its status or natural history, so little can be given in the way of management suggestions.

Comments: Formerly regarded as closely related to, if not conspecific with, M. xanthognathus, but morphological and chromosomal traits indicate a more distant kinship (see Musser and Carleton, in Wilson and Reeder 1993, 2005).