Arborimus longicaudus

Geographic Range

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 nearctic
  • native native

Habitat

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 temperate
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest

Physical Description

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.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger

Reproduction

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.

• Key Reproductive Features
• iteroparous iteroparous
• year-round breeding year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
• viviparous 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 altricial
• pre-fertilization
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• pre-independence
  • provisioning
  • protecting
    • female

Lifespan/Longevity

Nothing is known about the lifespan of A. longicaudus , but few voles live more than 1 to 2 years.

Behavior

Except for females with young, red tree voles are primarily solitary, though some display colonial tendencies in which clusters of nests have been found in a single tree. Males and females live apart, except during mating. Males burrow in the ground, whereas females maintain their nests in the trees. Nests are continually added on to from one generation to the next.

Red tree voles are nocturnal, foraging at night for a collection of needles, which they will bring back to the nests. The stored needles are then fed upon during the day, often while the animal is perched upon the top of a nest. When active during the day, the actions of these voles are slow and cautious. When disturbed from the nest, voles will run headlong down trees or jump from branch to lower branch until they reach ground whereupon they quickly seek cover.

It is thought that these animals have a limited ability to disperse and to colonize new habitats, possible because of extreme specialization on their conniferous habitat.

• Key Behaviors
• arboreal arboreal
• terricolous
• fossorial fossorial
• nocturnal nocturnal
• motile motile
• sedentary sedentary
• solitary solitary
• colonial colonial

Home Range

Home ranges, although not measured, are thought to be small, encompassing only one or two trees.

Communication and Perception

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 visual
• tactile tactile
• acoustic acoustic
• chemical chemical

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

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.

• Primary Diet
• herbivore herbivore
  • folivore folivore

• Plant Foods
• leaves
• wood, bark, or stems

• Foraging Behavior
• stores or caches food stores or caches food

Predation

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.

Ecosystem Roles

Arborimus longicaudus is an important food source for the northern spotted owl, which is an important predator of old-growth forests.

Economic Importance for Humans: Positive

Red tree voles hold no economic importance for humans.

Economic Importance for Humans: Negative

Red tree voles hold no economic importance for humans.

Conservation Status

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.

Other Comments

The taxonomy of A. longicaudus has been under debate for some time. It originally was classified under Phenacomys . The red tree vole was then placed in its own subgenus as Arborimus . Later this changed as further distinguishing information was gathered, indicated that the vole should belong to a separate new genus. These animals were once rare in museum collections, possibly because of their restricted habitat, but also because they are so small and occur so far up in the trees--making them somewhat unaccessible to study.

Additional Links

Encyclopedia of Life

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

Tamara Green (author), University of Wisconsin-Stevens Point, Chris Yahnke (editor, instructor), University of Wisconsin-Stevens Point.

References

Bury, B., P. Corn. 1986. Habitat use and terrestrial activity by red tree voles (Arborimus longicaudus). Journal of Mammalogy , 67(2): 404-406.

Carey, A. 1999. Red tree vole: Arborimus longicaudus . Pp. 620-622 in The Smithsonian Book of North American Mammals . Washington, D.C., and London: The Smithsonian Institution.

Carraway, L., B. Verts. 1998. Land Mammals of Oregon. . Berkley and Los Angeles, California: University of California Press.

Hamilton, J. W. 1939. American Mammals: Their Lives, Habitats, and Economic Relations . New York and London: McGraw-Hill Book Company, Inc.

Hayes, J. 1996. Arborimus longicaudus . Mammalian Species , 532: 1-5.

Manning, T., C. Maguire. 1999. A new elevation record for the red tree vole in Oregon: Implications for National Forest management. American Midland Naturalist , 142(2): 421-423.

Nowak, R. 1999. Walker's Mammals of the World, Sixth edition . Baltimore and London: The Johns Hopkins University Press.