As I trudge through a foot of snow, bundled from head to toe in multiple layers--I think about the animals. How are they getting along?
Some of them are faring quite well between the snow and the ground in that space called the subnivean zone. Snow traps the warmth of the earth and maintains a temperature of about 32 degrees.
The snow blanket enables small mammals to stay relatively warm and move around seeking food and mates.
Northern Michigan’s subnivean dwellers include voles, mice and shrews. Mice eat primarily seeds, voles eat mostly roots and other vegetation and shrews are carnivores. They eat insects, worms—and occasionally voles and mice!
All three create tunnels under the snow. Sometimes you can see these in the spring when the snow melts. They look like a tangled maze.
Which is how you’d like your tunnels to look if you wanted to use them to escape predators.
Just as these subnivean dwellers have developed ways to survive the winter, so have predators. Some of them have evolved ways of locating their prey under the snow.
Foxes and coyotes, for example, can hear rustling under the snow. When they’ve located a possible target, they leap into the air and pounce head first through the snow. With skill and luck, their paws land on a meal.
If you’re out walking this winter, you might spot a hole in the snow about the diameter of your thumb. This could be an entrance to a subnivean runway. These holes also serve as ventilation shafts so the subnivean dwellers aren’t overcome by carbon dioxide.
