In the News

Wildlife Copes with Winter
date posted: January 28 2004

By Heather Segale, Environmental Education Coordinator; and John Cobourn, Water Resource Specialist; University of Nevada Cooperative Extension

When the temperatures dip below freezing and the snow piles up in the mountains, it’s nice to be able to go home to a warm home that protects you from the elements. But, what do the animals do in the wintertime? It’s miserably cold out there when night falls and the temperatures drop. Winter is particularly stressful on wildlife, not only due to the cold, but also due to the lack of available food. That’s why each species has adapted strategies to survive the season. These strategies include migration to lower elevations, latitudinal migration (heading south), hibernation and changes in fur coats.

There are actually two species of weasel in the Tahoe Basin that change color when it gets cold in the winter to help them stay warm. “The coats of short-tailed and long-tailed weasels will turn white in the wintertime except for the tip of their tail, which will be black,” says Shawn Espanosa, Nevada Division of Wildlife. “Those white hairs lack pigment. Melanin is a pigment and it takes up space in the hairs. That space is now taken up by simply air, so the coat has more insulation capability.” With that extra insulation, the weasels are able to tough it out over the winter. It is also a defense mechanism to provide better camouflage from predators.

The pine martin and coyote grow a thicker coat to help keep them keep warm through the winter. Animals such as deer migrate to lower elevations when snow covers the mountains. Other animals, such as bears and marmots, hunker down in burrows or dens to sleep off the wintertime cold. Hibernation occurs as a physiological response to a lack of food (assuming they don’t have access to human garbage and are not disturbed by people snowmobiling, cross-country skiing or snowshoeing in the backcountry). Frogs do something similar to hibernation. They go into a torpor where they slow down their metabolic rate and hide out in a burrow.

In the winter, you can expect to see fewer wildlife species and fewer individuals within a species. For example, you will probably notice a significant reduction in the number of different birds at your bird feeder. However, you may still see the Mountain Chickadee, Pigmy Nuthatches, White-breasted Nuthatch and Red-breasted Nuthatch out and about. The Stellar Blue Jay is still around, but in fewer numbers and with much less noise than in the warmer months.

Birds such as osprey and bald eagles are lucky because Lake Tahoe doesn’t freeze over in the winter, so they can keep fishing throughout the year. In fact, you may even see more bald eagles at Lake Tahoe during the winter. Shane Romsos, wildlife ecologist, Tahoe Regional Planning Agency, tells us that eight to15 individual bald eagles are identified during an average winter. During the summer, we tend to have fewer bald eagles, with three documented nest sites. Not all of these nest sites are active each year, but there is usually at least one active nest site in any given year. Since bald eagles do not migrate but instead overwinter here at Lake Tahoe, they are extremely vulnerable. They need to conserve energy to maintain warmth, but they also need to expend the energy in order to get to food. Survival may be further compromised when we travel in their foraging areas.

Difficult winters can also have effects on the reproductive success of wildlife. Over time, declines in population can occur if animals cannot bear young, especially if they cannot find undisturbed sites for foraging. The local effects could be more significant than the effects nationally, so we have developed protected areas, habitat conservation and proposals to keep areas undisturbed. It’s a tough existence, and many animals simply don’t make it through the winter. We can help by respecting closures to specific areas and keeping domestic animals on leash so that they don’t disturb wildlife. If you plan to venture out into the forest this winter, it’s a good idea to be aware of the wildlife around you.

Watch for “The Lake Tahoe Report” in the North Lake Bonanza each Friday, and tune in to KOLO-TV News Channel 8 Tuesdays at 5 p.m. to learn more. Next week, learn more about Tahoe’s wildlife and how biologists use photo surveys to monitor for animals. “The Lake Tahoe Report” is a collaborative effort of the Lake Tahoe Environmental Education Coalition, University of Nevada Cooperative Extension, UC Davis and the USDA Forest Service. For more information, contact Heather Segale, University of Nevada Cooperative Extension, (775) 832-4138, or logon to www.lteec.org or www.unce.unr.edu.