67.2 Jan. 7 Seasonal changes in the diet of a non-hibernating high-latitude rodent: the northern red-backed vole, Clethrionomys rutilus. BRENNAN, April M.*; VAN TETS, Ian G. ; University of Alaska Fairbanks; University of Alaska Anchorage email@example.com
Rodents, such as lemmings and voles, which do not use hibernation and torpor, must choose foods that will enable them to meet their high energetic needs. These needs, and the food available to meet them, are likely to change seasonally. The aim of this study was to test whether free-living northern red-backed voles, Clethrionomys rutilus, preferentially ate items that were high in digestible energy and whether seasonal dietary changes correlated with changes in plant abundance and plant energy. We used stomach, cecum, and colon contents to assess diet and measured the gross energy and abundance of common plants found in our field sites. The voles' diet included a large proportion of hypogeous fungi from late spring through late fall with an increasing proportion of woody dicotyledonous plants (i.e. lowbush cranberry and paper birch) in October and November. Dicotyledonous roots contain vesicular-arbuscular mycorrhizae and are only common in the winter diet when epigeous fungi were rare in the field site. During spring thaw (April and May), the proportion of moss and young grass shoots increased to 35% of the diet. The changes in stomach contents were positively correlated with the gross energy content of plants. Our data support the hypothesis that voles preferentially eat energy rich and digestible foods but does not necessarily support the hypothesis that their diet changes due to plant abundance, as we could not measure the abundance of hypogeous fungi in our study sites. This study does, however, highlight the importance of hypogeous fungi to this species.