Mule Deer in Lemhi County - Winter Survival

While mule deer can be seen in town at any time of year, winter seems to be the time we are most likely to notice their presence. They appear in yards nibbling on shrubs or are seen crossing city streets. Why are they here and what attracts them to human communities? As mentioned in the first article of this series, mule deer are a migratory species. Winter weather forces them from their summer homes as cold and deep snow grip the land. Should the winter be mild, with warmer temperatures and little snow, mule deer may remain close to their summer range. But in most cases, the first snows of winter act to push the deer into lower elevation areas where food is still abundant and easy to find. These intermediate ranges provide important habitat in both the fall and spring as deer follow their food supply. Most deer enter winter with a good layer of stored fat that has been accumulated over the summer and autumn. The deer rely on this stored fat during winter to supplement the foods they find on their winter ranges. In most cases, this is sufficient to sustain deer that are relatively undisturbed through the winter even though they may lose 20% of their body weight. Foods that are actively sought are those with a lower fiber content, making them easier to digest. Such plants include grasses and forbs. And while many shrubs are avoided because of high fiber content and unpalatable essential oils, others such as big sagebrush, mountain mahogany, and bitterbrush are easier to digest than others. Deer will actively seek out these important winter food plants. Reducing fiber intake is important during all seasons but becomes especially important during winter when high amounts of fiber can impede the digestive process. Deer are small ruminants with a limited ability to digest fibrous roughage. Large volumes of such foods move slowly through the digestive tract and are of minimal nutritional value to the animal. In addition, many shrubs contain essential oils that disrupt the bacterial activity in the gut further slowing digestion. During normal winters, most deer are able to find sufficient low-fiber food sources by pawing through soft snow or by feeding in areas protected from heavy snowfalls. However, when winter snows become deep and temperatures plummet, deer will seek out food wherever they can find it, including your backyard. Unfortunately for mule deer, the very areas that are vital winter range are also very attractive places for people to live. Valleys provide warmer temperatures, less snow and protection from cold winter winds. These attributes combined with a scenic view make mountain valleys perfect places for towns to spring up and communities to grow. Scenery aside, deer utilize mountain valleys for their winter range for basically the same reasons we do. And this is where the problem starts. Homeowners in winter range find themselves with deer in their yard and the deer find a previous food source gone and possibly a fence blocking their progress. And since their instinct is to find food, they jump the fence and sample the ornamentals. Houses and property with dense trees and shrubs provide shelter for the deer. Initially, homeowners may enjoy having a deer or two in their yard. But over time, they may find not just a few animals, but many that are eating up every ornamental planting they have so carefully cultivated. Now the deer that are simply trying to survive become a nuisance. They crop buds and twigs from dormant shrubs and small trees. Perennial flower beds are targeted, especially those with early flowers such as tulips. Deer may even eat sunflower seed from bird feeders, swinging or tipping a feeder to spill its contents. The animals may even pose a danger for motorists as they dash in front of cars on city streets. With all these potential problems, co-existing with our mule deer may seem impossible. The best way to do this involves a variety of means from ensuring that healthy winter range is available to changing what we plant around our yards. In part three of this series, we will take a look at what can be done to help co-exist with our local deer population.