UNDER THE SNOW | Snowpack also provides protection from cold, with temperatures at the ground usually staying above freezing, allowing tiny meat-eaters like shrews to survive. They must consume 80 to 90 percent of their body weight daily, and can easily die if they fail to find food. Shrews are abundant in our forests, which indicates an even greater abundance of insects and other invertebrates! bigstockphoto.com/CreativeNaturePhotography
By WILL RICHARDSON | Moonshine Ink
At the Tahoe Institute for Natural Science, we are all about connecting people to Tahoe’s fascinating natural history. While nature is most easily enjoyed and appreciated during the summer, Tahoe’s winter ecology is equally intriguing. The season does present a host of challenges for our plants and animals, however, with cold, short days, often deep snow, and reduced access to or availability of food and other resources.
WINTER SURVIVAL | Relocating for the season, moving to an area where the climate is milder and resources easier to come by, is one option. This can mean migrating long distances to the south, as many of our breeding birds do, or simply shifting to lower elevations. Tahoe’s deer herds and mountain quail both practice the latter, walking over low passes and following drainages downhill. Photo by W. Richardson/TINSWINTER SURVIVAL | Another solution to meeting caloric needs during the winter is to dramatically reduce the expense side of the budget and simply take a long nap. There are many fine distinctions differentiating types of seasonal dormancy among the scientists who study that sort of thing, but they can all be thought of as variations of hibernation. Photo by W. Richardson/TINSWINTER SURVIVAL | The third strategy is to adapt to winter conditions and find a way to hang in there! This works well for rabbits, tree squirrels, some predators, and many resident bird species, all of whom get a jump on the summer breeding season in years when spring comes early. Photo by W. Richardson/TINSTHE SLEEPERS | Bear hibernation is driven by availability of food in the fall and early winter; if it’s abundant, many bears will remain active. This is easily observed in neighborhoods with ready access to garbage. However, females give birth during a dormant denning phase, so any pregnant females must hibernate, even if only for a short time. Photo by W. Richardson/TINSTHE SLEEPERS | Belding’s ground-squirrels are common residents of alpine meadows and grassy ridges at higher elevations. Males may spend up to nine months in hibernation, starting at the end of July. One of the longest dormancies of any mammal in North America, it is a testament to the considerable energy savings of dormancy strategies when food is scarce. bigstockphoto.com rck_953THE SLEEPERS | By far the most impressive are the Sierran tree frogs, which can freeze themselves solid for weeks, possibly months. Blood sugars serve as anti-freeze in vital organs and tissues, while ice-promoting nucleation agents flow to the spaces around those tissues, controlling where ice can and cannot form. Heartbeat and brain function cease completely until the frogs thaw with warmer temps. Photo by W. Richardson/TINSUNDER THE SNOW | Many animals gain protection from predators under a dense snowpack, staying active below in what is called the “subnivean zone.” Voles create extensive networks of tunnels, food caches, and nests, raising litters of young through the winter. In springtime, these are revealed as eskers of thatched grass and mud, a familiar sight. bigstockphoto.com/CreativeNaturePhotographyUNDER THE SNOW | Snowpack also provides protection from cold, with temperatures at the ground usually staying above freezing, allowing tiny meat-eaters like shrews to survive. They must consume 80 to 90 percent of their body weight daily, and can easily die if they fail to find food. Shrews are abundant in our forests, which indicates an even greater abundance of insects and other invertebrates! bigstockphoto.com/CreativeNaturePhotographyUNDER THE SNOW | Amazingly, some evergreen plants are able to perform limited photosynthesis beneath the snow, as longer wavelengths of the light spectrum can penetrate as much as 6 feet down. This provides an important jump on spring growth among plants that live in the arctic tundra, and likely benefits Tahoe’s evergreen shrubs like Mahala mat, chinquapin, and pinemat manzanita. Photo by W. Richardson/TINSROOTED TO THE GROUND | Short days and low sun angle make photosynthesis inefficient; lack of groundwater combined with strong winds result in desiccation; and freezing temperatures damage the cellular structure of leaves. Most of our plants get around this by either dropping deciduous leaves, dying back to the roots, or waiting until the next growing season as seeds. Photo by ninaphototahoe.comROOTED TO THE GROUND | Even though aspens drop their leaves, they are able to perform photosynthesis on warm winter days — in their bark! Mature bark cells are shed in a fine powder so that sunlight can penetrate the outer layers and reach photosynthetic pigments. As with shrubs photosynthesizing beneath the snow, this is an important trait in areas with long winters. bigstockphoto.com/PhotosiberROOTED TO THE GROUND | Extremely heavy snow loads are a great challenge. Junipers and Western white pines manage by growing stout and strong very quickly. Others, like mountain hemlock, stay flexible, especially where outer limbs are young and slim. The classic triangular Christmas tree shape of fir trees with down-angled limbs is particularly good for shedding snow and minimizing structural damage. Photo by W. Richardson/TINS
