Distribution and Abundance of Tree Voles in the Northern Coast Ranges of Oregon

Abstract

We sampled 86 randomly selected survey plots to evaluate the distribution and abundance of Red Tree Voles (Arborimus longicaudus) on the Tillamook and Clatsop State Forests in the northern Coast Ranges of Oregon in 2011–2013. We conducted surveys by visually searching for tree vole nests while walking along 500 m of transect in each plot. Trees with potential nest structures were climbed to determine if the structures were tree vole nests. We found tree vole nests in only 4 random plots, all of which were located near the coast, at the western edge of the Tillamook State Forest. Of 33 tree vole nests located, 20 (61%) were in old forests (≥80 y old), and 13 (39%) were in 1 plot in a young forest that was 65 y old. We concluded that tree voles were absent from most of the Tillamook and Clatsop State Forests, probably due to the fact that most of the area was either logged or burned in the early 1900s, and subsequently intensively managed on short rotations. We also suggest that remnant stands of old forest on Bureau of Land Management and state lands are acting as source populations from which tree voles populate adjacent young forests. Cuttings found in nests provided evidence that most of the voles were feeding on needles of Western Hemlock (Tsuga heterophylla) or Sitka Spruce (Picea sitchensis).