|Scientific Name:||Arborimus longicaudus (True, 1890)|
|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.
|Red List Category & Criteria:||Near Threatened ver 3.1|
|Contributor(s):||Linzey, A.V., Hammerson, G.A. & Roach, N.|
This species is assessed as Near Threatened because, 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. Further studies of this species' ecology and habitat use is needed to fully understand threats and extinction risk. This species could potentially qualify for Vulnerable under criterion B if occupied habitat has experienced significant declines.
|Previously published Red List assessments:|
|Range Description:||This species occurs along the coast and about 15 km inland north of Tillamook Head and Saddle Mountain in the northern Coast Ranges of Oregon (Price et al. 2015). However, it also possibly occurs 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.|
Native:United States (Oregon)
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The species is absent in northwest Oregon and is scattered where it occurs (Price et. al 2015). 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 vole's habitat is becoming increasingly fragmented throughout its range, so its area of occupancy and abundance likely are declining as well, but the rate of population 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|
|Habitat and Ecology:||Red tree voles occur in older coniferous forests in the Klamath Mountains and Somoma County (Dunk and Hawley 2009). They often 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); Arborimus longicaudus and A. 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. They are generally found in the largest available trees, commonly in the lower third of the live crown. Several nests may be built in large whorls of branches that 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 A. 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 a nocturnal species.
This species is threatened by timber harvesting, the depletion of important food sources, and low reproductive rates (Miller et al. 2010). Additional threats include loss of preferred old-growth forest habitat and forest fragmentation by clear-cutting 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 (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.
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 Rd 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:||Scheuering, E. 2018. Arborimus longicaudus. The IUCN Red List of Threatened Species 2018: e.T42615A22389366.Downloaded on 16 August 2018.|
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