Bison (<i>Bison bison</i>) activity fragments subnivean tunnels of small mammals

Abstract

Ecological interactions between ungulates and small mammals are generally not well understood. Here, we report an observation of unusually extensive small mammal (likely Meadow Vole [Microtus pennsylvanicus] or Tundra Vole [Microtus oeconomus]) tracks above the snow, exiting from trails and bed sites created by Bison (Bison bison) in northern Canada. We believe that weather and snow conditions were optimal for this observation. Although alteration of above-snow activity of small mammals in response to snow compaction by ungulates is probably not a rare event, it is not often reported. The effect on voles of exiting their subnivean tunnels as a result of Bison activity is unclear, but may be detrimental to their overwinter survival. Ungulate activity compacts snow, fragmenting small mammal tunnels resulting in loss of their insulative value for voles, and making it harder for them to dig new tunnels. Clearly, determining the effect of snow disturbance by gregarious ungulates on voles or other microtines, particularly regarding their overwinter survival, requires detailed investigation. Nevertheless, this observation provides new information on the ecological interactions between ungulates and small mammals, particularly from the boreal forest, where such information is largely lacking.