Out on a cross country ski on The Grand Mesa, we enjoyed a Colorado Bluebird Day. Bluebird days are defined as the day after a snowstorm, when the sun comes out and the new fallen snow sparkles. It doesn’t get much better than going skiing on a crisp, sunny day with fluffy powder snow blanketing the forest.
We decided to break trail through the woods, following the blue diamonds tacked to the trees. Our dog, Simon, accompanied us on our nordic ski adventure, bounding through the snow. Up and down, he loped, with his black plume of a tail swishing behind him.
Finally, at one point, he stopped, sniffing in the snow, like a bloodhound on the trail of a thief.
“Simon, come on, let’s go!”
But, still we could not get him to come. He would not be deterred. His black head continued to burrow deeper and deeper into the snow.
Suddenly, he jerked his head out of the snow. Something gray caught my eye.
“Oh my God, what is that?”
Sitting on top of his nose was a small gray mouse. As he jerked his head, the mouse went flying through the air into the woods. The entire episode seemed comical, yet preposterous at the same time. It also startled the heck out of Simon. For the rest of our ski, he kept his nose out of the snow.
Our adventure, made me wonder — where was that mouse living with several feet of snow on the ground? How did he survive winter at 11,000 feet?
In winter, when feet of snow cover the ground, there is a small layer of open space between the ground and the snow. The warmth of the ground causes this by melting off the snow, forming a wator vapor. The water vapor forms ice crystals on the lowest layer of snow, sort of making a roof for that space between the snow and the ground.
This life zone is referred to as the subnivean zone, and many small animals reside there during the winter, including mice and voles. These small critters will sleep, store food, and wonder around in these tunnels under the snow. They will also come out above the snow through small holes or vents. These holes also allow the carbon dioxide they exhale to escape.
You might think living under the snow protects them from predators like coyotes, lynx, and foxes. Not so, as most of these predators have excellent hearing and can actually detect the noises of these small rodents. Coyotes have been known to collapse their “vents’, thus trapping them under the snow, where they can easily be killed and eaten.
Next time you are out for a snowshoe walk or cross country ski, look more closely at the snow that surrounds you. You might see tracks or even these entry holes for the life below your feet. Though the winter world of the Rocky Mountains can seem silent, know that a teeming ecosystem is going on all around you.