After over 10 years as an academic, I forget sometimes that I’ve accumulated a vocabulary that most other people have never heard of. Every now and then, I’ll throw a word into a conversation or program that will leave people gazing back at me blankly, brows furrowed in confusion.
The thing is, I don’t do it to impress anyone. I use them because there just isn’t another word out there that better describes what I’m trying to say.
Subnivean is one of those words. I figured that since we’re on the subject of snow, (and we’re getting more of it as I write this), it would be a good time to bring it up.
Subnivean is a great word. Once you break it down, it’s quite simple. Sub = under, nivea = snow. Basically, it refers to anything that is found under the snow. Most of the time, it’s used to describe the habits of animals that are found living under the snow.
There are actually quite a few of them. Small mammals, like mice, voles, lemmings and shrews are too small to grow a winter coat of fur when things get cold. That much hair would make walking a challenge. Instead, they take advantage of a rather ubiquitous source of insulation: snow. The white stuff is an excellent insulator. On days out here when the mercury drops down well below -30 degrees C, the temperature at the bottom layer of snow, right where it’s in contact with the ground, is still hovering around the freezing mark, a much more comfortable temperature for our furry little friends.
That bottom layer of snow is quite a bit different from the rest of the layers above it. It’s referred to as the pukak layer (an Inuit term) and is usually very crystaline, almost like sugar. This type of structure makes it easy for mice and voles to create an entire network of tunnels completely hidden from the hungry eyes of predators.
That doesn’t mean they are completely safe. Predators like weasels and mink can follow them down into the tunnels, while foxes and owls listen for them from above (a story for another day). Still, with lots of readily-available food, shelter and relative safety, being subnivean isn’t a bad way to be for a small mammal.
However, there are reasons to come ‘top-side’ now and then. The pukak layer can be compacted by snow collapsing or from people walking or driving snowmobiles over it, making the substrate impenetrable. It can also get hard to breathe down there. With all sorts of critters running around in what is essentially a closed environment, CO2 can build up, making it necessary to punch a few air holes to clear things out (above).
So next time you’re out for a walk in the snow, keep your eyes peeled for the subtle signs of our subnivean neighbours.