Annual and seasonal variability in tundra vole ( <i>Microtus oeconomus</i> ) diet in northern Alaska

Within arctic ecosystems, rodents (voles and lemmings) influence plant community composition, soil nutrient availability, and carbon cycling through foraging and the deposition of waste. Yet, little is known about how rodent diet may vary seasonally and annually, particularly with fluctuations in population density. Here, we characterize diet composition of tundra voles (Microtus oeconomus) in northern Alaska using stable isotope analysis of fecal and hair samples collected over a seven-year period, including a full “boom and bust” population cycle. Results from Bayesian mixing models from both fecal and hair samples suggest that tundra voles in northern Alaska predominately feed on the rhizomatous sedges Eriophorum vaginatum and Carex bigelowii throughout the summer. However, consumption shifts from rhizomes in early summer to tillers and buds in late summer. Tundra vole diets were broadly similar from year to year throughout the population cycle, although dietary niche breadth increased with population abundance. These findings on the selective dietary behavior of the tundra vole provide insight into plant–animal interactions in the Alaskan tundra, which may be disrupted under climate change or by shifts in other disturbance regimes.