DEMOGRAPHY AND RESOURCE USE BY MICROTINE RODENTS NEAR TOOLIK LAKE, ALASKA, USA

Five species of microtine rodents occurred in tundra near Toolik Lake, but only tundra voles Microtus oeconomus and singing voles M. miurus were widespread and abundant. Tundra voles reached their highest densities (50 ha-1) in low, wet habitats dominated by rhizomatous monocotyledons and primarily ate monocotyledons. Singing voles reached similar densities in more mesic habitats that contained relatively high availability of dicotyledons and horsetails and mostly ate dicotyledons and horsetails. Both species of voles began breeding in the spring before snowmelt was complete and were still breeding when the first heavy snows occurred in autumn. However, tundra voles began breeding a few weeks earlier than singing voles, and singing voles had slightly larger litters than tundra voles (average of 8.4 vs. 7.1 for adults, respectively). Population fluctuations appeared to be synchronous in the 2 species, which suggests control of their densities by similar environmental factors. The differences in food preference and habitat use suggest that competitive interactions between these species are weak and unlikely to be a major factor influencing their abundance. -from Authors