Mycophagy of red-backed voles in Oregon and Washington

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Abstract
We analyzed stomach contents from two subspecies of Clethrionomys californicus and three subspecies of C. gapperi from coniferous 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 fruticose lichens, regardless of season. Fungus consumption partially depended on availability. When fungi became scarce, lichens were substituted. Other foods were important only during winter in Cascade Range. Clethrionomys gapperi from Washington consumed large quantities of conifer seed and green plant parts in midautumn. These materials were a small part of the diets of Oregon red-backed voles in midautumn, but this may relate to localized small seed crops. Dependence on ectomycorrhizal fungi by western red-backed voles probably accounts for the latter's disappearance from deforested sites.