Common name: Oregon red tree vole, Tree mouse

Scientific Name: Arboretums longicaudus

"Arbor"= tree; "mus"= mouse

"longus"=long; "caudus"= tail

Description: This vole is 16-20 cm (6-8 inches) in length, including a tail that is over one-third its total body length.. The tree vole weighs between 1-1.5 ounces (25-47 grams). Its coloration varies from dark reddish brown along the northern coast to lighter reddish brown along the middle of its range, to orangish red along the southern coast and western flank of the Cascade Mountain range. The underside of the tree vole is light gray and the tail varies in color from rich medium brown to black (Maser 1998).

Geographical range: This vole is found in Western Oregon from South of the Columbia River to just south of the Smith River, just below the Southwestern Oregon boarder in California. It has never been found North of the Columbia River, in Washington, British Columbia, or Alaska (Maser 1998).

Habitat: The Oregon red tree vole usually inhabits coniferous forests, although they have been documented to live in mixed-coniferous/deciduous forests. They mostly reside in the mid-to upper-canopy of Douglas fir trees (Psuedotsuga menziesii), but occasionally on the coastal regions are found in the canopies of Sitka Spruce (Picea sitchensis) and old-growth Western hemlock (Tsuga heterophylla) trees. These voles can only inhabit trees that are at least 25-30 years old because immature trees are not structurally developed to support the voles nesting requirements or to protect them from severe weather (Maser 1998).

Reproduction: Male and female tree voles build separate nests and live in them year round, only to encounter when the female is fertile. The female has a litter size of one to four offspring. The babies are born naked, blind, and helpless. A female can become fertile within 24 hours of giving birth to her babies, thus sometime more than one litter occupy a nest at a given time. The offspring remain in the nest until they are at least one month old, at which time the move to another part of the same tree and construct their own nest (Maser 1998).

Input requirements (food supply): Oregon tree voles are one of the most specialized tree-dwelling organisms in the world. They feed primarily on the needles of Douglas fir trees and to a lesser extent on the soft bark or pithy center of a small twig. They also sometimes eat the needles of Sitka spruce, Grand fir (Abies grandis), and Western hemlock trees. The voles cut their twigs at night, drag them back to the nest, and consume them in or on top of their nest site or store them for future consumption. When a tree vole eats a coniferous needle, it bites along the edge of the needle and removes a part of the needle called the "resin duct". Once both resin ducts are removed, it consumes the entire needle. Young needles are often consumed without the removal of their resin ducts (Maser 1998). It has been estimated that tree voles eat an average of 100 Douglas-fir needles per hour (Kritzman 1977) Tree voles obtain their water from their food and from licking dew drops off of the coniferous needles (Maser 1998).

Role in the ecosystem: Oregon tree voles are an important food source for raccoons, weasels, martens, and various other owl species. Northern spotted owls are their most common predator (Maser 1998).

Use as a Human Resource: The Oregon red tree vole is important to humans because it is an indicator species. Tree vole populations are threatened when forests are fragmented. Thus, when their populations decline it is an indication that the forest where their population is declining is under great environmental stress.

Notes: In an old-growth forest, many generations of tree voles can live in a single Douglas fir tree. Nests are built over 150 feet above the forest floor in ancient forests and 60-70 feet above the forest floor in second growth forests. As a tree grows, its lower branches become shaded and die. Thus, the red tree vole will leave the lower nest atop dead branches and make a new nest higher in the canopy on live branches. In order to maximize its foraging efficiency and protect itself from predators, the vole tends to build its nest on branches with live needles where it can obtain food in close range (Maser 1998).

Oregon tree voles build nests out of harvested twigs, sometimes building atop of an already preexisting, but abandoned, bird or small mammal nest. Their nest begins as a pile of twigs and needle resin ducts. As the nest debris accumulates, the vole begins to burrow a hole, pushing nesting debris to the side and overhead as if to create a small dome. As the vole feed on top of the nest and inside of the nest, it adds to the accumulation of debris and its nest grows ever so larger. The nest is passed down to generations as the parents die, and in effect the nest grows larger and larger. In order for the tree vole to access the exterior of the nest, it creates various tunnels. All tree vole nests have an escape route that leads from the interior of the nest to below the nest. There is also at least one tunnel that leads from the interior of the nest to the roof, where the vole feeds on its stash. These tunnels are usually situated so that the vole does not have to be exposed to the outside for long periods of time when it is getting its food. Sometimes a nest can be so large, it surrounds the entire trunk of the tree (Maser 1998).

If a tree vole is being attached by its predator it via a tunnel that leads to the bottom side of the nest and onto the tree trunk. The vole then scurries, head first, down the trunk of the tree and hides under leaves or bushes on the forest floor. Another way it escapes is by running onto the branches of nearby trees, scurrying into a dense patch of branches and standing still. The tree vole’s reddish coat enables it to blend in nicely with the bark of the tree or it appears to resemble a Douglas-fir cone. The third way a tree vole can escape a predator is by jumping from the tree into the air and falling to the ground. The tree vole can fall from a height of 60 feet and almost always lands on its feet, unharmed. They appear to spread their legs and tail which aids them for a softer landing and allows them to cling onto any underbrush they may fall upon (Maser 1998).