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Arborimus longicaudusred tree vole

By Tamara Green

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. (Hayes, 1996)

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. (Bury and Corn, 1986; Hayes, 1996; Manning and Maguire, 1999)

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. (Carraway and Verts, 1998; Hayes, 1996; Nowak, 1999)

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. (Carraway and Verts, 1998; Hayes, 1996; Nowak, 1999)

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. (Carey, 1999)

  • Sexual Dimorphism
  • female larger
  • Range mass
    25 to 50 g
    0.88 to 1.76 oz
  • Average mass
    37 g
    1.30 oz
  • Range length
    166 to 187 mm
    6.54 to 7.36 in
  • Average length
    170 mm
    6.69 in

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. (Nowak, 1999)

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. (Carraway and Verts, 1998; Hayes, 1996)

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. (Carey, 1999; Carraway and Verts, 1998; Hayes, 1996; Nowak, 1999)

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. (Carey, 1999; Hayes, 1996; Nowak, 1999)

The young are weaned at 30 to 35 days of age. (Nowak, 1999)

  • 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

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. (Hayes, 1996; Nowak, 1999)

  • 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

Lifespan/Longevity

Nothing is known about the lifespan of A. longicaudus, but few voles live more than 1 to 2 years. (Nowak, 1999)

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. (Carraway and Verts, 1998; Hamilton, 1939; Hayes, 1996; Nowak, 1999)

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. (Carraway and Verts, 1998; Hamilton, 1939; Hayes, 1996; Nowak, 1999)

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. (Carey, 1999)

Home Range

Home ranges, although not measured, are thought to be small, encompassing only one or two trees. (Carey, 1999)

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. (Nowak, 1999)

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. (Carey, 1999; Hayes, 1996)

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

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. (Carey, 1999; Carey, 1999; Carey, 1999; Carraway and Verts, 1998; Hayes, 1996)

Ecosystem Roles

Arborimus longicaudus is an important food source for the northern spotted owl, which is an important predator of old-growth forests. (Manning and Maguire, 1999)

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. (Hayes, 1996; Nowak, 1999)

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. (Carey, 1999; Hayes, 1996; Nowak, 1999)

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

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

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

fertilization

union of egg and spermatozoan

folivore

an animal that mainly eats leaves.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

herbivore

An animal that eats mainly plants or parts of plants.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

year-round breeding

breeding takes place throughout the year

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 D Wilson, S Ruff, eds. 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.

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