Deeryards are forested areas used by deer for shelter during winter, and deer at the northern extremes of their range are highly dependent on deeryards for survival. Deeryards include a core area composed of mature softwoods and a hardwood browse area that may occur within the core, or more frequently as young openings located around the periphery of the core.
Depending on location, the softwood component primarily consists of mature balsam fir, spruce, northern white cedar, pine or eastern hemlock. The canopy species provide many advantages such as reduced snow depth, lower wind velocity, increased temperatures and higher relative humidity at the ground level. On sloped terrain, south-facing deeryards are preferred as they receive more sun and less snow during winter.
In some instances, steep south-facing slopes with hardwood species in the canopy can be deeryards. The steep terrain and south-facing aspects combine to minimize snow accumulation and wind chill. Understory vegetation within the stand should be dense enough to provide shelter from prevailing winds and browse for deer. To meet these requirements, stands need at least 50 percent crown closure. For small deeryards (less than 50 acres) 70 to 100 percent crown closure is preferred. Softwood species need to be approximately 35 feet tall to be functional, so a stand must be older than 30 to 40 years.
In addition to the thermal advantages, deer migrate to deeryards because the lower snow accumulation combined with packing of snow on trails greatly decreases the energy spent walking and foraging. The improved travel ability also enhances predator avoidance, and these attributes allow deer to slow the loss of their fat reserves and increase their chance of winter survival. When snow depths reach the point where deer sink more than 18 inches, they typically remain on trails within the deeryard and abandon all other areas.
While deeryard is the term commonly used, deer wintering area (DWA) is a more accurate description. Steve Weber, chief of wildlife for the New Hampshire Fish and Game Department, began working with DWAs in 1980. Steve describes DWAs as analogous to big rubber bands that expand and contract in size depending on winter severity. That is, deer use a larger or smaller component of the DWA depending on snow depth and temperature. Moderate weather allows deer more mobility and the ability to use larger portions of the DWA, while severe weather may restrict deer to the most dense softwood cover.
Yarding is routinely observed across Canada, New England, upstate New York, the upper Great Lakes region, the upper Midwest and the Northwest. Whitetails may also yard up in more southerly regions for short periods during extreme winters or in high elevation areas. Whitetails may travel considerable distances to reach DWAs. The exact distance depends on temperature and snow depth, elevation of fall range and distance to wintering habitat.
In Maine and Minnesota, deer travel an average of 6 to 10 miles from summer to winter ranges, but movements of 20 to 30 miles have been documented. Deer travel a little farther in Quebec, as 18- to 36-mile migrations are common. In southern New England, most deer travel less than 5 miles to reach DWAs because winters are less severe and the DWAs have been reduced to remnants of their original size. They neither draw nor support large numbers of deer.