Under the Snows

Today I headed out for a ski up towards Robertson Glacier in Peter Lougheed Provincial Park. The weather was overcast with a slight sprinkling of new snow. As we headed up the valley towards the glacier, we decided to dig a snow pit to evaluate the avalanche hazard. Starting as usual I began digging but it didn't take long to discover that this wasn't going to be any ordinary snowpit. By the time we'd finished digging, the pit was eight feet deep--by far the deepest I've ever had to excavate. This was just another sign of the unusually high snowfalls in the Rockies this year. By the way, there was about a two foot slab sitting atop a nasty sliding layer.

As we passed a group of half a dozen ptarmigans waddling through the snow, my thoughts began wandering back to the snowpit and onto the life under that eight foot snowpack. While many animals including myself, are struggling to stay on top of the snow, a number of others spend the winter traveling beneath its heavy blanket.

During early winter, you may see signs of mice and voles traveling across the snow surface in search of food, but after the snowpack reaches between 15 and 25 cm, they retreat under the snow. For the remainder of the winter, they'll forage at ground level. Eventually, they will establish a series of runways that allow them to move around freely. Unfortunately, the snows this year have not made their runway construction easy. On cold years with strong depth hoar formation, it's fairly simple to move about, however this year the weather has not cooperated. Not only did our snowpit, and others this season, show little sign of significant depth hoar, but the November rains have left several hard icy layers just above the surface--no one said life in the mountains was easy.The pika is another animal that spends the winter traveling under the snow (known as the subnivean environment). During the summer it's constantly collecting plants to help it get through the long winter. This year they're going to need a good supply to last them well into the spring as they are generally found at higher altitudes where the snowfalls are the heaviest.

One of the biggest dangers to subnivean animals is an early cold spell. If the temperatures turn cold before the snow is deep enough to provide ample insulation, there can be a large die off of both plants and animals that rely on the snow for protection from the cold.

Once the runways have been developed and enough snow accumulated to provide a constant near 0°C temperature, they can remain fairly active through-out the winter with little worry of blizzards and bottomless snow. They are not completely free of predators though as animals like the coyote and the snowy owl are quite adept at tracking down their dinner right through the snow.