The Subnivean World

Subnivean. The word sounds like it could be referring to the homeworld of a race of space giants in a science fiction novel, but it’s actually a very down-to-earth term and this time of year is the perfect time for its use. “Sub” of course means below. “Nivean” comes from the latin word “nives,” which means snow. So “subnivean” means “beneath the snow.”

A prairie vole at Coyote Ridge Natural Area in Fort Collins, CO. Photo by Jamie Simo.
A prairie vole at Coyote Ridge Natural Area in Fort Collins, CO. Photo by Jamie Simo.

You wouldn’t know it to look at it, but under that fresh layer of new-fallen snow lies an entire ecosystem. Unlike chipmunks, rodents like mice and voles don’t hibernate during the winter and, right beneath your feet, they may be busy carving out elaborate tunnels leading from one clump of tasty grass or seeds to another. Some of those tunnels are so elaborate they consist of a number of chambers for different functions like eating, sleeping, caching food, and urinating.

The secret of the subnivean world is the snow itself. Snow is actually a fantastic insulator as long as it’s not too wet, which you may know from learning about Eskimos and their igloos. That’s because snow is comprised of ice crystals with pockets of air between them. This trapped air holds onto heat, meaning that the air between the ground and the first layer of snow pack stays fairly constant around 32 degrees Fahrenheit no matter what the temperature or weather conditions above.

Diagram of the subnivean zone by Marco Cibola. http://archive.audubonmagazine.org/truenature/images/ice_Castle-marcocibola-lg.jpg
Diagram of the subnivean zone by Marco Cibola. http://archive.audubonmagazine.org/truenature/images/ice_Castle-marcocibola-lg.jpg

This fairly constant, relatively warm air allows insects and microbes to survive in some of the harshest conditions around, which, in turn, provide food for those before-mentioned rodents. The snow also helps protect small mammals by screening them from predators, though it’s not a magic bullet. Many predators, like owls, have hearing so sensitive that they can detect the sounds of their prey moving under the snow. The great grey owl, for instance, can hear a mouse under up to 18 inches of snow!

So, now that you know about the subnivean world, try slipping the term into conversation the next time you’re at happy-hour and see what happens. Who knows, you might find you’re the life of the party!

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