We examined stomach contents of 426 Clethrionomys, 217 C. californicus from western Oregon and 209 C. gapperi from widely scattered areas across North America. Clethrionomys californicus consumed fungi of 28 genera. Clethrionomys gapperi from the Rocky Mountains westward consumed fungi of 23 genera, whereas C. gapperi east of the Rocky Mountains consumed fungi of 7 genera. This study supports the conclusions of an earlier study, limited to Oregon and Washington, that food habits of C. californicus and C. gapperi are more closely related to habitat than to species or subspecies of vole.
Maser, Chris and Maser, Zane
"Mycophagy of red-backed voles, Clethrionomys californicus and C. gapperi,"
Great Basin Naturalist: Vol. 48
, Article 16.
Available at: http://scholarsarchive.byu.edu/gbn/vol48/iss2/16