Community Organization of Arvicoline Rodents in Northern Alaska

Abstract

The community organization of arvicoline rodents was studied on 18 live-trapping grids near Toolik Lake on the North Slope of Alaska. At moderate densities, tundra voles were more abundant on grids with more wet habitat, with more highly preferred food (cotton grass) and with less shrub cover, singing voles were more abundant on grids with less wet habitat, with more highly preferred food (horsetail) and with more cover, and collared lemmings were more abundant on grids with more highly preferred food (willow) and with less cover. Tundra vole and singing vole populations were negatively associated, probably because of their very different habitat preferences. At low densities, experimental manipulation of food, cover and competing species on the same 18 grids revealed different effects on the arvicoline species. Abundance of tundra voles increased with supplemental food, but singing voles and collared lemmings showed no significant responses. Singing vole populations had a clear negative response, but tundra voles and collared lemmings had no significant response to removal of shrub cover. Similarly, collared lemmings showed no response to removal of tundra voles or singing voles, and tundra voles showed no response to removal of singing voles, but singing voles showed a negative response to removal of tundra voles. The apparent mutualistic relationship between tundra voles and singing voles probably resulted from an indirect effect via predation, i.e., more predation on singing voles when tundra voles were removed. We conclude that the community organization of arvicoline rodents near Toolik Lake is strongly influenced by availability of preferred foods and by predation but less so by interspecific competition, at least when densities are low