Tree voles: an evaluation of their distribution and habitat relationships based on recent and historical studies, habitat models, and vegetation change

Abstract

We describe the historical and current distribution of tree voles (Arborimus longicaudus; A. pomo) and compare the minimum density of trees with tree vole nests in different forest age-classes based on museum records, field notes of previous collectors, tree vole nest surveys conducted by federal agencies, and our field studies in Oregon and California. We conclude that tree voles are still fairly common in old forests within much of their historical range, but have become uncommon or rare in some areas as a result of fire and logging. Our analysis of food stored at red tree vole (A. longicaudus) nests in Oregon indicated that the vast majority of tree voles feed almost exclusively on needles of Douglas-fir (Pseudotsuga menziesii). However, tree voles in the Sitka spruce zone of northwestern Oregon feed primarily on western hemlock (Tsuga heterophylla) and Sitka spruce (Picea sitchensis). Historical field notes from the California coastal region also documented occasional voles that feed on grand fir (Abies grandis), Monterey pine (Pinus radiata), or Bishop pine (P. muricata). We used the program MaxEnt to develop predictive models of tree vole presence based on an a priori set of habitat, structure, and climate variables. Based on a comparison of potential vole habitat in historical and recent vegetation maps, we estimated that the geographic distribution of red tree voles in Oregon contracted by 23 percent in the period 1914–2013.