red tree vole (Arborimus longicaudus)
Tree voles are endemic (native) to the humid coniferous forests west of the crest of the Cascade Mountains in Oregon and northwestern California. The red tree vole occurs in western Oregon from the Cascade crest to the Pacific coast, with a geographic range covering approximately 16.3 million acres across multiple land ownerships. Voles, however, were found to be uncommon or absent in much of the North Coast Range and North Cascades of Oregon. The range of the dusky tree vole is not clearly delimited within this area, but it is generally attributed to the northern Oregon Coast Range. Historically, tree voles collected north of Eugene and west of the Willamette Valley were typically classified as the dusky tree vole, while those collected north of Eugene and east of the Willamette Valley were almost all identified as red tree voles. There is not yet complete resolution in the scientific community as to whether or not the dusky tree vole is a valid subspecies of the red tree vole (Arborimus longicaudus). Information provided below specific to the red tree vole also applies to the dusky tree vole unless otherwise noted. Tree voles are small rodents less than 8 inches long, and weighing up to 2 ounces. A long, fur-covered tail accounts for about 50 percent of the vole's total length. Their thick coats range in color from reddish-brown to orange-red. The darker coat color is characteristic of the dusky tree vole.
- States/US Territories in which the red tree vole, North Oregon Coast DPS is known to or is believed to occur: Oregon
- US Counties in which the red tree vole, North Oregon Coast DPS is known to or is believed to occur: View All
- Countries in which the the red tree vole, North Oregon Coast DPS is known to occur: United States
|Status||Date Listed||Lead Region||Where Listed|
|Pacific Region (Region 1)||North Oregon Coast population|
» Candidate Information
» Federal Register Documents
» Conservation Plans
No conservation plans have been created for red tree vole.
» Life History
Because of their exclusive diet of conifer needles, tree voles are restricted to conifer forests. Though they use a variety of tree species, they principally feed on Douglas-fir needles and nest in Douglas-fir trees. However, tree voles in a portion of the North Coast Range are associated with Sitka spruce and western hemlock forests. Although tree voles occur and nest in younger, second-growth forests, they tend to be more abundant in, and strongly select for, older forests. Nests tend to be found in the larger-diameter trees within a stand. Expanses of land without suitable forest cover can be a barrier to tree vole movement and population connectivity.
Tree voles live in tree tops and rarely come to the forest floor. They are one of the few animals that can persist on a diet of conifer needles, which is their principle food. Conifer needles are unpalatable to most animals because they have resin ducts that contain chemical compounds (terpenoids), which act as a deterrent to herbivory. Tree voles, however, are able to strip away these resin ducts and eat the remaining portion of the conifer needle. Piles of these resin ducts on the ground may be seen under trees where tree voles have foraged. Tree voles are mainly active at night. When they are outside of their nest, they spend much of their time gathering live conifer branchlets, upon which they feed. They may feed away from the nest but more often they bring the branchlets back to the nest to cache or to feed themselves or their young.
Nests are constructed of branchlets, discarded resin ducts, and other materials, ultimately shaped into a sphere with interior tunnels. As nests continue to be occupied, more material is added and they can become quite large, sometimes completely encircling the tree trunk. Nests of females tend to be larger than those of males. Adult tree voles lead solitary lives, with the males and females only coming together to breed. Red tree vole litters are small relative to similar rodent species, averaging just under 3 young per litter. Adult females are capable of becoming pregnant immediately after giving birth, resulting in some females having two litters of different-aged young in the nest. Juvenile tree voles develop more slowly than similar sized rodents, and donít disperse from the nesting area until they are 47 to 60 days old. Tree voles have very limited home ranges, often less than 0.5 acre, and their typical dispersal distance is often less than the length of a football field.
The taxonomy of the red tree vole is complex and not yet resolved. Early researchers concluded that the dusky tree vole, found in the northern Oregon Coast Range in Lincoln, Tillamook and Clatsop Counties, was a subspecies of the red tree vole. More recent research indicates the complexity in reaching an unequivocal conclusion on the subject. One study could not find genetic differences between red tree voles and those classed as dusky tree voles. Conversely, another study found that red tree voles break out into three genetically distinct groups, one of which overlaps the range of the putative dusky tree vole. The most recent research on this topic, comparing body measurements between red tree voles and those classed as dusky tree voles, found significant differences between the groups; the differences were subtle, however, and the variables measured could not be used to reliably discern red tree voles from dusky tree voles.
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