Mammal Species of the World
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Red tree voles, Arborimus longicaudus, are native to the Pacific Northwestern region of North America. Theya re found in the coniferous forests of Oregon and Norhtern California. They are present on the western side of the Cascade Mountains. The precise limits of the species distribution are unknown.
Biogeographic Regions: nearctic (Native )
endemic to a single nation
Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: (20,000-200,000 square km (about 8000-80,000 square miles)) 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.
Dorsal coloration of A. longicaudus is either a bright rusty-brown, or a uniform cinnamon. The venter is whitish. Tails are either black or brown. Juveniles are distinguished by duller coats, displaying more brown than red and having tails that are black. Red tree voles have soft long hair. Arborimus longicaudus shows sexual dimorphism in that females tend to be larger than males. Claws are replaced by nails on their first digit.
Mass for this species is reported at 25 to 50 g, with an average mass of 37 g. Length ranges between 166 and 187 mm, with an average of 170 mm.
This species is not sympatric with any other similar voles. Another member of the genus, Arborimus pomo is found in northern California, and is similar in size and color. However, the two species can be easily distinguished by range, as well as the fact that each has a different number of chromosomes.
Range mass: 25 to 50 g.
Average mass: 37 g.
Range length: 166 to 187 mm.
Average length: 170 mm.
Sexual Dimorphism: female larger
Other Physical Features: endothermic ; bilateral symmetry
Length: 21 cm
Weight: 47 grams
Size in North America
Average: 172 mm males; 184 mm females
Range: 158-206 mm
Range: 25-47 g
Differs from Arborimus albipes in being reddish with a hairy tail (versus brown or gray with a scantily haired tail). Clethrionomys californicus is much darker red and has a shorter tail.
Central and Southern Cascades Forests Habitat
The Oregon slender salamander is endemic to the Central and Southern Cascades forests ecoregion. The Central and Southern Cascades forests span several physiographic provinces in Washington and Oregon, including the southern Cascades, the Western Cascades, and the High Cascades, all within the USA. This ecoregion extends from Snoqualmie Pass in Washington to slightly north of the California border. The region is characterized by accordant ridge crests separated by steep, deeply dissected valleys, strongly influenced by historic and recent volcanic events (e.g. Mount Saint Helens).
This ecoregion contains one of the highest levels of endemic amphibians (five of eleven ecoregion endemics are amphibians) of any ecoregion within its major habitat type. The threatened Northern spotted owl has been used as an indicator species in environmental impact assessments, since its range overlaps with 39 listed or proposed species (ten of which are late-seral associates) and 1116 total species associated with late-seral forests. Late-seral forests in general are of national and global importance because they provide some of the last refugia for dependent species, and perform vital ecological services, including sequestration of carbon, cleansing of atmospheric pollutants, and maintenance of hydrological regimes.
There are a number ofl amphibian taxa present in the Central and Southern Cascades ecoregion; the totality of these amphibian taxa are: the Rough-skinned newt (Taricha granulosa); the endemic and Vulnerable Shasta salamander (Hydromantes shastae); the endemic and Vulnerable Oregon slender salamander (Batrachoseps wrighti); the Endangered Dunn's salamander (Bolitoglossa dunni); the Northwestern salamander (Ambystoma gracile); the Near Threatened western toad (Anaxyrus boreas); the Vulnerable Oregon spotted frog (Rana pretiosa); the Near Threatened Cascades frog (Rana cascadae); Coastal tailed frog (Ascaphus truei); Near Threatened Larch Mountain salamander (Plethodon larselli); California newt (Taricha torosa); Pacific giant salamander (Dicamptodon ensatus); Cope's giant salamander (Dicamptodon copei); Monterey ensatina (Ensatina eschscholtzii); the Near Threatened Foothill yellow-legged frog (Rana boylii); Northern Red-legged frog (Rana aurora); Pacific chorus frog (Pseudacris regilla); Van Dyke's salamander (Plethodon vandykei), an endemic of the State of Washington, USA; Long-toed salamander (Ambystoma macrodactylum); and the Olympic torrent salamander (Rhyacotriton olympicus).
There are a moderate number of reptilian species present in the ecoregion, namely in total they are: Western pond turtle (Emys marmorata); Western fence lizard (Sceloporus occidentalis); Sharp-tailed snake (Contia tenuis); Ringed-neck snake (Diadophis punctatus); Rubber boa (Charina bottae); California mountain kingsnake (Lampropeltis zonata); Yellow-bellied racer (Coluber constrictor); Western rattlesnake (Crotalus viridis); Western gopher snake (Pituophis catenifer); Common garter snake (Thanophis sirtalis); Northwestern garter snake (Thamnophis ordinoides); Western skink (Megascops kennicottii); Southern alligator lizard (Elgaria multicarinata); and the Northern alligator lizard (Elgaria coerulea).
There is a considerable number of avifauna within the Central and Southern Cascades ecoregion; representative species being: Flammulated owl (Otus flammeolus); Western screech owl (Megascops kennicottii); White-tailed ptarmigan (Picoides albolarvatus); and White-headed woodpecker (Picoides albolarvatus).
There are a large number of mammalian taxa in the ecoregion, including: Bobcat (Lynx rufus); Wolverine (Gulo gulo); California ground squirrel (Spermophilus beecheyi); Yellow-bellied marmot (Marmota flaviventris); Ermine (Mustela erminea); Fog shrew (Sorex sonomae), an endemic mammal to the far western USA; Hoary marmot (Marmota caligata); Mountain beaver (Aplodontia rufa); and the Near Threatened red tree vole (Arborimus longicaudus); Yellow pine chipmunk (Tamias amoenus); and the American water shrew (Sorex palustris).
Red tree voles typically inhabit old-growth forests, though they have been found in second-growth forests as well. They prefer the wet habitat provided in old-growth forests that contain mainly Douglas fir (Pseudotsuga menziesii). However, they are found in stands consisting of Sitka spruce (Picca sitchensis), grand fir (Abies grandis), and western hemlock (Tsuga heterophylla). These voles are arboreal in nature, building nests in various regions of the canopy, though one study showed greater accumulations of nests to be found in the lower canopy.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: forest
Habitat and Ecology
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.
Comments: 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 sawtimber stands; young stands may serve as barriers to dispersal (A. B. Carey, in Wilson and Ruff 1999). It is an arboreal vole that exhibits 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 overstory, 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).
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.
Red tree voles are folivores with a highly specialized diet, feeding almost solely on Douglas fir needles. Red tree voles will use other conifer needles and bark in their diet, but in more minimal quantities. Studies done in labs have shown that they will eat other foods, but the voles will quickly die if deprived of their specialized diet. They obtain water from the foliage contents and also as dew on the needles. This may be important, as their habitat is limited to the moist, foggy forests where such condensation forms readily.
Plant Foods: leaves; wood, bark, or stems
Foraging Behavior: stores or caches food
Primary Diet: herbivore (Folivore )
Comments: Feeds on Douglas-fir needles. Also eats grand or lowland white fir, Sitka spruce, and western hemlock needles. May eat tender bark of twigs as well as the pithy center. Usually feeds inside or on top of its nest.
Arborimus longicaudus is an important food source for the northern spotted owl, which is an important predator of old-growth forests.
Taking to the trees is thought to be one of the vole's adaptations to avoid terrestrial predators. However, these small rodents are subject to predation by raptors and a few climbing mammals such as fishers, martens, and raccoons. The most common predator of red tree voles is the northern spotted owl (Strix occidentalis), which is a federally listed threatened species. Red tree voles make up 50 % of this owl's diet.
- northern spotted owls (Strix occidentalis)
- fishers (Martes pennanti)
- American martens (Martes americana)
- raccoons (Procyon lotor)
This list may not be complete but is based on published studies.
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 21 - 80
Comments: 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. This vole is relatively difficult to observe and trap, so existing records likely do not reflect the full distribution of the species.
10,000 - 1,000,000 individuals
Comments: Total adult population size is unknown but likely exceeds 10,000. This vole is relatively difficult to capture, so existing records likely do not reflect the true abundance of the species.
Thought to have very limited dispersal capability (Thomas et al. 1993). Predators include spotted owls, raccoons, etc.
Life History and Behavior
No studies have been done on communication in this species. However, other voles are known to use vocalizations, tactile communication, some visual signals, and scents. It is likely that A. longicaudus communicates with conspecifics in a similar fashion.
Communication Channels: visual ; tactile ; acoustic ; chemical
Perception Channels: visual ; tactile ; acoustic ; chemical
Comments: Active throughout the year.
Nothing is known about the lifespan of A. longicaudus, but few voles live more than 1 to 2 years.
The reproductive system of this species has not been reported. Males and females do not live together, so it is unlikely that they are monogamous.
Females and males do not have much contact with each other. Males live in burrows in the ground during non-mating periods, whereas females keep to the nests in the trees. However, males will climb the trees, building smaller temporary nests, during mating season. This allows them to breed with the females.
Most breeding occurs from February to September, but these animals have been reported to breed throughout the year. Litters consist of one to three young. The estrous cycle lasts on average 5.9 days. The length of gestation is variable, lasting from 27 to 48 days. The gestation is longer in lactating females, although the mechanism for this delay has not been reported. This species is known to undergo postpartum estrous.
At birth, young weigh 2 to 3 g. Growth is slow compared to other species of voles. This slow growth and development may be an adaptation of this species to the poor food quality of pine needles.
The young are weaned at 30 to 35 days of age.
Breeding interval: These animals are reportedly capable of producing about three litters per year.
Breeding season: Breeding is year-round, but most occurs between February and September.
Range number of offspring: 1 to 3.
Range gestation period: 27 to 48 days.
Average gestation period: 28 days.
Range weaning age: 30 to 35 days.
Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous
The female red tree vole takes care of the young. Males are only present during the breeding season. The young of this species are altricial. The females cares for the young until they are slightly more than 36 days old.
Parental Investment: no parental involvement; altricial ; pre-fertilization (Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning, Protecting: Female)
Breeds 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 2-3 (range 1-4). Newborns are altricial, able to leave nest in 1 month.
Logging has contributed to population declines and in some areas extinction. Due to this vole's high dependency upon a specific diet in primarily old-growth forests, they are vulnerable to fragmentation and loss of habitat. Arborimus longicaudus has come under protection via management strategies in the federal forests where it exists. This has been due to its lack of adaptability as well as its importance in the diet of endangered spotted owls.
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: near threatened
IUCN Red List Assessment
Red List Category
Red List Criteria
National NatureServe Conservation Status
Rounded National Status Rank: N3 - Vulnerable
NatureServe Conservation Status
Rounded Global Status Rank: G3 - Vulnerable
Reasons: Restricted distribution in western Oregon and perhaps extreme northwestern California; prefers old-growth forest habitats that are being eliminated and fragmented by large-scale timber harvesting.
Intrinsic Vulnerability: Moderately vulnerable
Comments: 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.
Environmental Specificity: Very narrow. Specialist or community with key requirements scarce.
Comments: Diet and microhabitat are specialized, and the old growth habitat is no longer common.
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).
Global Short Term Trend: Relatively stable to decline of 30%
Comments: 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).
Global Long Term Trend: Decline of 50-70%
Comments: Distribution has been reduced and continues to decline (Corn and Bury 1988, 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.
Degree of Threat: Very high - high
Comments: Threats include loss of preferred old-growth forest habitat and forest fragmentation by clearcutting practices (Thomas et al. 1993, Verts and Carraway 1998).
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.
Biological Research Needs: Little is known of the basic biology of this species (Verts and Carraway 1998), including food habits, population genetics, and dispersal.
Global Protection: Several (4-12) occurrences appropriately protected and managed
Comments: Several occurrences 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.
Needs: The red tree vole may benefit from existing/proposed conservation measures for the spotted owl (Thomas et al. 1993).
Relevance to Humans and Ecosystems
Red tree voles hold no economic importance for humans.
Red tree voles hold no economic importance for humans.
Red tree vole
The red tree vole (Arborimus longicaudus) is a species of rodent in the family Cricetidae. It is found only in coastal forests of Oregon and northern California. They eat exclusively the needles of conifers, mostly Douglas-fir (Pseudotsuga menziesii) and occasionally other species. They often spend their lives in just one tree, and many generations will live in different parts of the same tree.
When eating Douglas-fir needles, they carefully remove the fine resin ducts (which resemble coarse, straight hairs) along each edge of the needle, discarding these or using them for nest lining. (see image below) They are nocturnal and very difficult to see, but they can be detected by finding piles or wads of these resin ducts on the ground.
Red tree voles are about 6-8 in long, including the tail. They have a reddish-brown coat.
|Wikimedia Commons has media related to Arborimus longicaudus.|
- Linzey, A.V. & NatureServe (Scheuering, E. & Hammerson, G.) (2008). Arborimus longicaudus. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 21 March 2009. Database entry includes a brief justification of why this species is of near threatened
- Musser, G. G. and M. D. Carleton. 2005. Superfamily Muroidea. In Mammal Species of the World a Taxonomic and Geographic Reference (D. E. Wilson and D. M. Reeder eds.). Johns Hopkins University Press, Baltimore.
- Whitaker, J. 2009. National Audubon Society Field Guide to Western Mammals.
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Names and Taxonomy
Comments: Johnson and George (1991) described as a new species (Arborimus pomo) California populations previously regarded as Arborimus (or Phenacomys) longicaudus, based on chromosome differences (diploid number of 40 or 42, vs. 52 in northern range of A. longicaudus), smaller overall size, and certain skull and muscle differences. Musser and Carleton (in Wilson and Reeder 1993, 2005) and Baker et al. (2003) accepted A. pomo as a species distinct from A. longicaudus.
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) (which also lack consistently verifiable morphological differences). 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.
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); 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.