Mycophagy of red-backed voles in Oregon and Washington

We analyzed stomach contents from two subspecies of Clethrionomys californicus and three subspecies of C. gapperi fromconiferous forests of Oregon and western Washington. Seasonal diets were determined for each subspecies of C. californicus.Major foods eaten were the fruiting bodies of hypogeous ectomycorrhizal fungi, predominantly Gasteromycetes, and fruticoselichens, regardless of season. Fungus consumption partially depended on availability. When fungi became scarce, lichens weresubstituted. Other foods were important only during winter in Cascade Range. Clethrionomys gapperi from Washingtonconsumed large quantities of conifer seed and green plant parts in midautumn. These materials were a small part of the diets ofOregon red-backed voles in midautumn, but this may relate to localized small seed crops. Dependence on ectomycorrhizal fungiby western red-backed voles probably accounts for the latter's disappearance from deforested sites.