Phenacomys intermedius (Heather vole) is found on the western mainland of the U.S. as far south as New Mexico. In Canada the vole is found across northern Canada from Labrador to the Yukon Territory. (Banfield 1974)(Fitzgerald 1994)

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: (>2,500,000 square km (greater than 1,000,000 square miles)) Southwestern British Columbia and adjacent Alberta, Canada,Labrador west to southwestern Yukon Territory, south through south through the Olympic Mountains, Cascade Range, Sierra Nevada, and Rocky Mountains to northern New Mexico, central Utah, and northern California, and disjunctly to east-central California and western Nevada (Wilson and Reeder 1993). Generally above 750 m in the western U.S. and to above 3000 m in the Rockies and California.

The Heather vole fur is long and soft. The color varies geographically. Generally, the dorsal colors are brown to grayish, while the ventral fur is gray. The feet are white to gray and the ears can have orange hairs. The tail is slightly longer than the hindfeet (31-34 mm) and has dark fur on top and is pale on the ventral side. The total length of the animal is between 130 and 140 mm. The species closely resembles the Meadow vole; skull characteristics are often needed to help tell the species apart. The skull characteristic used is that the cheek teeth have deep lingual angles in the Heather vole. (Banfield 1974; Fitzgerald 1994)

Range mass: 30 to 50 g.

Average basal metabolic rate: 0.375 W.

Length: 15 cm

Weight: 41 grams

• Terrestrial

The Heather vole lives in stands of spruce, lodgepole pine, aspen, and grassy meadows in montane forest, subalpine, and alpine tundra (Fitzgerald 1994). The vole usually stays close to water. The Heather vole has been seen traveling 200 yards from its nest. The understory of their habitat may contain shrubs such as blueberry, dwarf birch, and soapberry. The Heather vole has been found as high as 12,100 feet elevation in Colorado. (Banfield 1974; Fitzgerald 1994; Armstrong 1972)

Terrestrial Biomes: tundra ; taiga ; forest ; mountains

Comments: Sea level to above treeline; open coniferous forest with heath, shrub understory; shrub areas on forest edge; mossy meadows in forests; alpine tundra with cover. Nests on ground under snow (winter) or in burrow (summer).

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 Heather vole searches for green vegetation, bark of trees and shrubs, twigs, seeds, berries, and fungi. Their diet consists of leaves and fruits of willows, myrtle blueberry, snowberry, bog birch, kinnikinnnik (bearberry) in the summer months. In the winter, spring, and fall they tend to focus more on the bark and buds of willow, birch, and blueberry. The Heather vole stores food for use in the summer and winter. The food reserves are found close to the burrow entrances. (Banfield 1974; Fitzgerald 1994).

Comments: In winter, feeds on bark and buds of shrubs and heaths. In summer, feeds primarily on green vegetation, berries, and seeds. Stores food winter and summer.

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

Estimated Number of Occurrences: 81 to >300

Comments: At least hundreds of known locations.

10,000 to >1,000,000 individuals

Density estimates range from 0.5 to 10 per ha in different habitats in different areas. Irregular population fluctuations are typical. Solitary in summer except during breeding season. Family groups may occupy communal nests in winter.

Comments: Active throughout the year.

Heather voles have several estrus periods per year. Most of the breeding occurs between May and September. However, the voles located at higher elevations have a shorter season than the voles at lower elevations. Heather voles have a gestation period of 19 to 24 days. The litter size varies between 2 and 9, but variation is large because of the differences in litter sizes between adult and juvenile females. Adult females produce larger litters (average 5.9), while the juvenile females produce smaller litters (average 3.8) their first season. Three litters per year is believed to be the maximum produced. The voles are born blind and deaf. They finally wander out of the nest at about 3 weeks of age. Males don't reach sexual maturity until the next spring, while females reach sexual maturity 4-6 weeks after birth. (Banfield 1974; Fitzgerald 1994)

Average birth mass: 2.18 g.

Average gestation period: 22 days.

Average number of offspring: 4.58.

Average age at sexual or reproductive maturity (female)

Sex: female: 37 days.

Gestation lasts 19-24 days. Young are born mid-June to early September, though the season possibly is more restricted at high elevations. Litter size averages 3-4 for young-of-year, 4-6 for older females (which may produce 2 litters per year) (McAllister and Hoffman 1988).

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Reasons: Wide distribution in western North America; many protected occurrences; no known large-scale threats.

Global Short Term Trend: Unknown

Comments: Unknown

Degree of Threat: CD

Global Protection: Many to very many (13 to >40) occurrences appropriately protected and managed

Comments: Protected in Wilderness Areas and National Parks and Provincial Parks of British Columbia, Alberta, Washington, Oregon, Montana, Utah, and elsewhere.

The only adverse affect known at this time is the Heather vole has been known to carry the virus listeriosis (Banfield 1974).

There are no known ways that the Heather vole positively benefits humans at this time.

Comments: MtDNA data (Bellinger et al. 2005) indicate species-level differences among red tree vole (Arborimus longicaudus or Phenacomys longicaudus), Sonoma tree vole (A. pomo or P. pomo), white-footed vole (A. albipes or P. albipes), and western heather vole (P. intermedius) but no clear difference between the two Oregon subspecies of red tree voles (longicaudus and silvicola). These data further indicate a close relationship between tree voles and A. albipes or P. albipes, validating inclusion of albipes in Arborimus. Bellinger et al. (2005) did not find that P. intermedius clustered with Microtus. Bellinger et al. (2005) noted that recognition of Arborimus as a distinct genus is subject to interpretation of data.

There is uncertainty about the taxonomic status of Phenacomys ungava. In recent decades, most authors have regarded ungavaas a subspecies of P. intermedius. Musser and Carleton (in Wilson and Reeder 1993, 2005) noted the present validity of earlier statements that the relationship between intermedius and ungava needs further detailed study; nevertheless, they listed P. ungava as a separate species. Jones et al. (1997), Baker et al. (2003), and George (in Wilson and Ruff 1999) also recognized ungava as a distinct species.