Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Rodentia Cricetidae

Scientific Name: Arborimus longicaudus
Species Authority: (True, 1890)
Common Name(s):
English Red Tree Vole
Taxonomic Notes: Johnson and George (1991) separated California populations previously regarded as Arborimus longicaudus and described them as a new species Arborimus pomo, based on chromosome differences, smaller overall size, and certain skull and muscle differences. Musser and Carleton (in Wilson and Reeder 1993, 2005) and Baker et al. (2003) included this new species.

There is no consensus on the proper generic allocation for this species. It was placed in the genus Arborimus by Johnson and George (1991), Musser and Carleton (in Wilson and Reeder 1993, 2005), Hayes (1996), Adam and Hayes (1998), and Baker et al. (2003); and included in the genus Phenacomys by Carleton and Musser (1984), Repenning and Grady (1988), and Verts and Carraway (1998). Bellinger et al. (2005) noted that recognition of Arborimus as a distinct genus is subject to interpretation of data.

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): Linzey, A.V. & NatureServe (Scheuering, E. & Hammerson, G.)
Reviewer(s): Amori, G. (Small Nonvolant Mammal Red List Authority) & Chanson, J. (Global Mammal Assessment Team)
Listed as Near Threatened, although it has a large extent of occurrence it is restricted to old growth forests, and there is the ongoing threat from logging in old-growth, which both reduces and fragments its habitat. Almost qualifies as threatened under criterion B.
Previously published Red List assessments:
1996 Lower Risk/least concern (LR/lc)

Geographic Range [top]

Range Description: This vole occurs in western Oregon, on the west slope of the Cascade Range as far south as the Douglas-Jackson county line, and in the Coast Range to the California border, and on some buttes and low mountains between the major ranges (Verts and Carraway 1998), at elevations of up to 1,600 meters (Manning and Maguire 1999). However, this species possibly occurs also in northern California (see Hayes 1996). Murray (1995) presented DNA information suggesting that specimens from south of the Smith River drainage in Del Norte County, California, were more similar to the Oregon tree voles than to other California populations.
Countries occurrence:
United States
Upper elevation limit (metres): 1600
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: The total adult population size is unknown but likely exceeds 10,000. It is relatively difficult to capture, so existing records probably do not reflect the true abundance of the species.

Verts and Carraway (1998) mapped approximately 100 collection sites in Oregon; these represent certainly several dozen distinct occurrences or subpopulations, but the number of extant occurrences is unknown. The species' habitat is becoming increasingly fragmented rangewide, so the vole's area of occupancy and abundance likely are declining as well, but the rate of decline is unknown (probably less than 30% over the past 10 years). Its distribution has been reduced and continues to decline (Corn and Bury 1988; Verts and Carraway 1998).
Current Population Trend: Decreasing
Additional data:
Population severely fragmented: Yes

Habitat and Ecology [top]

Habitat and Ecology: Red tree voles inhabit mixed evergreen forests; optimum habitat consists of wet and mesic old- growth Douglas-fir forest and various other mesic habitats, including those dominated by grand fir, Sitka spruce, or western hemlock (Johnson and George 1991); P. longicaudus and P. pomo (sensu Johnson and George 1991) exhibit no habitat differences. The species is rare in sapling, pole and managed saw timber stands; young stands may serve as barriers to dispersal (A. B. Carey, in Wilson and Ruff 1999). They are arboreal voles that exhibit some terrestrial activity.

Nests are 2-65 m above the ground, in trees of any size, often in Douglas-fir, generally in the largest available trees, commonly in the lower third of the live crown; several nests may be built in large; whorls of branches provide support for nests in young trees; large branches of old-growth trees can support large maternal nests or nurseries; nests are sometimes built in cavities and hollows in trees or under the moss covering large branches of old trees (Biswell et al., no date; Carey, in Wilson and Ruff 1999). Gillesberg and Carey (1991) found 117 nests and nest fragments in 50 felled Douglas-fir trees; they classified nest trees predominantly as overstorey, vigorous, and with intact tops; of four cavities found in felled trees, two contained red tree vole nests. In northern California, nests of tree voles (probably P. pomo) were most abundant in old-growth forests; associated with large-diameter Douglas-fir, high percent canopy cover, high stump density, low snag density, shorter snags and logs, and lower elevation; all nests were in Douglas-fir, mostly adjacent to trunk on south side (Meiselman and Doyle 1996).

Red tree voles breed throughout the year, but most litters are born February-September. Females may breed within 24 hrs of giving birth. Gestation is 28 days but may be extended to 48 days in lactating females (Carey, in Wilson and Ruff 1999). Litter size usually is two to three (range one to four). Newborns are altricial, and are able to leave the nest in one month.

This species is thought to have a very limited dispersal capability (Thomas et al. 1993). Predators include spotted owls, raccoons, etc. Red tree voles feed on Douglas-fir needles. They also eat grand or lowland white fir, Sitka spruce, and western hemlock needles. It may eat tender bark of twigs as well as the pithy centre. They usually feed inside or on top of their nest. It is nocturnal.
Systems: Terrestrial

Threats [top]

Major Threat(s): Threats include loss of preferred old-growth forest habitat and forest fragmentation by clearcutting practices (Thomas et al. 1993; Verts and Carraway 1998).

The relatively low reproductive potential of this vole (C. Maser pers. comm.) may reflect the difficulty of converting conifer needles into energy for metabolism (Carey, in Wilson and Ruff 1999). This species appears to have limited dispersal capabilities. Early seral stage forests may be a barrier to dispersal.

This species has very narrow environmental specificity; its diet and microhabitat are specialized, and its old growth habitat is no longer common.

Conservation Actions [top]

Conservation Actions: Several occurrences of the red tree vole are in protected areas. The Survey and Manage program required the U.S. Forest Service to survey for certain logging-sensitive species (including the red tree vole) throughout areas subject to timber sale and to provide adequate no-logging buffers if such species are found. Some vole protection was eliminated in March 2004 when the Survey and Manage provisions of the Northwest Forest Plan were withdrawn. Subsequent litigation may affect the ultimate outcome of this situation.

The red tree vole may benefit from existing/proposed conservation measures for the spotted owl (Thomas et al. 1993). In addition, little is known of the basic biology of this species (Verts and Carraway 1998), including food habits, population genetics, and dispersal.

Citation: Linzey, A.V. & NatureServe (Scheuering, E. & Hammerson, G.). 2008. Arborimus longicaudus. The IUCN Red List of Threatened Species 2008: e.T42615A10729936. . Downloaded on 13 October 2015.
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