Arborimus – Tree voles

A small but remarkable group of rodents found only in the Pacific Northwest of the United States. Unlike most voles, which are ground-dwelling creatures, tree voles live high up in coniferous forests, particularly in Douglas-fir trees. This arboreal lifestyle makes them unusual in the rodent world and gives them the nickname “tree mice.”

Their strong dependence on conifers, especially Douglas-firs, makes tree voles unique. They almost exclusively eat conifer needles, stripping them off twigs with sharp incisors. This is unusual because needles are tough, low in nutrients, and full of resins that many animals cannot tolerate. Yet tree voles thrive on them, carefully peeling away resin ducts before chewing. They build elaborate nests made of chewed fir needles and twigs high in the forest canopy, where they spend nearly their entire lives. In fact, some tree vole nests can become quite large, with layers of old and new material built up over time, serving as both sleeping quarters and food storage. Their ability to live almost invisibly above the forest floor is one of the reasons they are so rarely seen, even in places where they are common.

They are mostly solitary, though multiple individuals may sometimes share a large nest. They are nocturnal, moving through the branches at night to feed and gather materials. Their small size, soft reddish or brown fur, and long whiskers make them well-suited for life in the treetops, but their specialized diet also makes them very vulnerable to habitat loss. Old-growth forests are especially important for them, since these provide the dense canopy and steady supply of Douglas-fir needles that the animals rely on. Because of this dependency, the red tree vole is considered a sensitive or threatened species in much of its range, and conservation efforts often focus on protecting the forest habitats it calls home.