If you live where the snow is actually melting, a labyrinth of vole tunnels may be revealing itself to you. These tunnels were excavated in the snow next to the ground in what is referred to as the subnivean layer. They lead from sleeping areas to known sources of food, and are advantageous to both mice and voles that travel in them – they provide thermal insulation by protecting them from the wind and cold, and they keep these rodents hidden from predators. Carbon dioxide, which builds up in the subnivean layer from animal respiration as well as CO₂ released from the ground, escapes through ventilation shafts, or air vents, that lead up to the surface of the snow.
Voles stay in these tunnels as long as the snow is deep enough not to expose them, finding food in the form of plants, seeds and bark from bushes and shrubs as they dig through the snow. This winter has provided voles, mice and shrews with an extended period of protection, as hungry barred owls attest to.
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