The winter months are here. Frigid temperatures cause some animals to hibernate or move south for the winter. But did you know there is life beneath the snow?
Animals like moles, lemmings, mice, and insects live down under the snow cover in a layer called the subnivean layer. An intricate system of tunnels, sleeping quarters, even latrines are carved out under the snow, leaving a relatively safe space for the animals to live.
The subnivean zone (from Latin “sub” – under and “nives” — snow) is formed after the first snowfall sticks to the ground. The snow falls onto dead plants, hardy vegetation, and hanging rocks, blocking the snow from accumulating underneath.
Snow that falls on the ground sublimates, meaning it changes from a solid to a gas without going through the melting stage. Sublimation is prompted by the heat radiating from the earth. The warm, moist water vapor rises into the bottom layer of snow, which cools, condenses, and refreezes into tightly packed snow, making a roof.
It only takes six inches of snow for the subnivean animals to have a sturdy roof over their heads. Add another two inches and the under-snow temperature will remain at a constant 32 degrees F, regardless of the temperature and weather of the outside world. The subnivean layer is a great place for small mammals to hide from the bitter cold as well as predators.
Some predators, however, use the tunnel system to their advantage. The short-tailed weasel uses tunnels to keep warm and to hunt the moles and mice living inside.
Another predator, the red fox, preys on the animals underneath. Their hearing is amazing. They stand above the snow and listen. At the first sound of movement, they will jump head first into the snow with their hind legs sticking straight up into the air.
As spring comes and the snow melts, the incredible tunnel system starts to show. Tunnels from dens and food supplies can be seen by the outside world. This is our only glimpse into the ecosystem living beneath the snow and once the green grass appears, all evidence of this life vanishes until the next snowfall.