March 2007

Living in Jackson Hole throughout the winter season, we are constantly either removing snow from where we do not want it or searching for soft snow to recreate in. One thing is certain, however, we have seen dramatic changes in the overall condition of our snow this season. This scenario includes human inhabitants as well as thousands of small mammals that inhabit our winter world all season. More specifically, what might be the perspective of a long-tailed weasel on the changing snow conditions? I thought about this recently after cross-country skiing with a small group of friends. As we looked out on the peaceful quiet of a snow-covered field, some of us perceived the large open field of dead space-void of singing birds and green grass-as nothing more than a frigid cold, wind-swept blanket of snow. Their impression was that of a desolate, lifeless world. I offered a much different perspective, And here is why.

There are entire neighborhoods of animals and animal activity beneath the blanket of snow where we were looking. They are living there-active, well-fed and warm for the most part-because of one main tenet of physics that many small animals understand: Air acts as an insulator. For the long-tailed weasel-a fearless and incredibly agile carnivore-and other animals that have chosen not to hibernate or migrate when winter hit Jackson, the options are adapt or perish. One important adaptation is to live life under the snow, right at the boundary between the earth and the snow pack (the area that winter ecologists call the 'subnivean'). Unpacked snow contains air, and lots of it. The amount of air to insulate the ground, and our wild inhabitants, is dependent on the physical make-up of the snow pack; how dense the snow is, the number and types of hard ice layers that develop within the snow pack and the total depth of snow. Shallow, dense snow packs often mean a cold subnivean world: cold air will penetrate downward. Deep, uncompacted snow on the other hand offers a warm protective layer. How warm? Given that evening winter temperatures in our valley can drop to minus 25 degrees Fahrenheit and the earth with an adequate insulating layer of snow is a near constant 32 degrees Fahrenheit, I know where I would rather spend the evening! The physical structure of the snow crystals at the 'earth-snow boundary' is also important to our little long-tailed weasel. Here, ice crystals often 'grow' in large, elegant shapes, including ice cups, some the size of your small fingernail, creating a secret new world full of air pockets and large crystals that form a barrier as easy to tunnel through for the weasel as we would move through a pile of balloons. The long-tailed weasel is not the only creature taking advantage of this cozy winter 'subnivean' world. Now add thousands upon thousands of small rodents such as mice, shrews and voles that are living beneath our seemingly quiet, uninhabited snow-covered field... Beginning to get the real picture? It is a snow-covered world of seeds, dormant grass and berries that feed rodent populations, along with inquisitive and effective predators perfectly shaped to tunnel under the snow in search for prey.

If only for a few brief moments, I wish I could magically turn the white blanket of snow transparent. Thus I could stand on the deck of the Nature Center and witness one of nature's most long-held secrets. A world in motion with animals moving and tunneling the snow here and there, of animals collecting and storing seeds, of little animals huddled together at night in nests lined with bison fur and of other snow-dwellers engaged in the never-ending game of predator-prey, like our long-tailed weasel. Through it all, I hope all of us will look upon the next peaceful, quiet, snow-covered field we come across and see our winter world from a whole new perspective…and gain a new level of appreciation.

3 Creek Ranch home owners please stop in or give a call to the Nature Center to share a story or two, relax by the fire or learn more about our winter world here on the Ranch.

Respectfully,
Roger Smith
Resident Naturalist
Director of Outdoor Pursuits