Arborimus longicaudus
red tree vole

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)

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)

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)

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

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)

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)

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)

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; Carraway and Verts, 1998; Hayes, 1996)

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)

Red tree voles hold no economic importance for humans.

Red tree voles hold no economic importance for humans.

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)

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)