Arborimus longicaudus

The red tree vole (Arborimus longicaudus) is a small rodent found in the coastal mountains and western Cascades of Oregon. This vole has a unique life history and highly specialized ecological niche.  Of the approximately 70 vole species worldwide, the tree vole is unique in that it lives its life in the canopy of old-growth forests rather than on the ground. Due to their arboreal nature, relatively little is known about the critter.

Red tree voles are small, usually 6-8 inches including their long tail.  Their coats vary depending on location ranging from dark reddish brown towards the northern range, lightening to an orange-red and cinnamon along the southern coast.  Their feet are long and wide, adapted for climbing. They are nocturnal, secretive, and vital to coastal forest ecosystems.

Douglas Fir needles are their only food source, as well as their only water source.  Moisture from rain and fog is licked off of the needles.  The resin ducts are then removed and the internal needle eaten.  Young red tree voles must eat excrement from adults to obtain bacteria to digest the pine needles.  

Nests are built up to 100 feet above the forest floor, mainly next to the trunk, or in the dense foliage of old-growth outer branches.  Their nests are very intricate; they are passed down from generations and are continuously built upon.  Each nest has a “bathroom,” a ceiling where eating takes place, and an escape route that runs from the bottom of the nest down the trunk of the tree.  These nests are extremely susceptible to storm damage.  The nests require the support of mature trees, and most red tree voles are found in old-growth trees.  

Red tree voles make up about half the diet of northern spotted owls.  They are also prey for raccoons, marten and fishers as well as other owl species.  Because of the red tree vole’s relationship to these animals, as well as their need for old-growth trees, the red tree vole is an indicator species for old-growth habitat.  

Unfortunately, they are difficult to find.  Researchers must examine the forest floor for discarded resin ducts, as an indication of recent feeding.  Then they must climb the trees to search for nests.  Over the last several years, dedicated citizens have formed survey teams; trained people in tree climbing and surveyed dozens of timber sales for red tree vole nests. Many sales were modified and vole nests were buffered due to this grassroots effort to protect the old-growth forests of the Pacific Northwest.

While they are not currently listed with the Endangered Species Act, red tree vole populations are declining due to clear-cutting and other non-sustainable forestry practices. In Oregon, the red tree vole is listed as a Species of Concern. Unfortunately, protections for the red tree vole were eliminated in March 2004 when the Bush administration withdrew the Survey and Manage provisions of the Northwest Forest Plan.