Tahoe Institute for Natural Science: Animals that benefit from deep snow
March 4, 2018
The recent shift in weather has people hoping for another "Miracle March," a term coined in 1991 when it snowed 20 feet during that month after a long period of drought.
It could happen again and, we certainly hope so! Sierra snow is not only vital for Tahoe's recreation-based economy and the summer water supply on both sides of the range, but also helps many of our local animals withstand Tahoe's winters.
Many of Tahoe's animals flee the freezing temperatures of winter and others sleep away the difficult months. Yet few people realize that throughout the winter, with temperatures regularly dipping well below freezing, many small species including voles, shrews, mice, and other rodents, remain active underneath the snow, which acts as an insulating layer.
Throughout the cold months, in the "subnivean zone" — the area between the surface of the ground and the bottom of the snowpack — animals are protected from the harsh conditions above. It takes only 5 to 6 inches of snow for small rodents to have a covering layer to hide under. Add only a few more inches, and the subnivean zone remains slightly above 32 degrees Fahrenheit, regardless of the temperature and weather conditions of the world above. In addition, depending on the density of the snow pack, certain wavelengths of light can penetrate through up to 6 feet of snow, allowing some photosynthesis and plant growth to occur, providing snacks for animals facing the winter in the subnivean zone.
In Tahoe's winter wonderland, there are five species of animals that turn from the color of dirt in the summer, to white in the winter. These include long- and short-tailed weasels, snowshoe hare, white-tailed jackrabbit, and of course my favorite, the white-tailed ptarmigan; a mountain chicken that changes its feathers to welcome winter's arrival instead of flying south (like so many birds do).
Both temperature and photoperiod (also known as daylight length) trigger hormonal changes in each of these species to undergo a molt, replacing fur or feathers with those of another color. These transformations allow each animal to better camouflage in their surroundings and prevent them from being eaten, or for the carnivorous weasels, escape detection as they hunt prey (including the smaller rodents that live in the subnivean zone).
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You can imagine how difficult it would be for an animal that turns completely white during the winter, to stay hidden from predators with little or no snowpack.
We too are an animal that relies on a deep winter snowpack. We enjoy the snow that provides us the many recreational activities on the slopes or in the backcountry. Far more importantly, the snow serves as our largest water reservoir, with an estimated 23 million Californians directly relying on Sierra Nevada snow for their water supply.
As the snowpack slowly melts through the spring and summer, it provides water for our agricultural needs, along with water for drinking, cooking, cleaning and other industrial needs. And of course, the local plants and animals use that water also.
So with all of that being said, be sure to pray, dance, or hope for a Miracle March, as the snow is extremely vital for many creatures in the Tahoe region.
We naturalists at the Tahoe Institute for Natural Science (TINS) seek to advance the natural history, conservation, and ecosystem knowledge of the Tahoe region through science, education, and outreach. If you would like to learn more about Tahoe's natural history, join us on one of our many free nature tours, as we explore Tahoe and teach the public about the animals and plants that reside here. To learn more, visit us at http://www.tinsweb.org.