Minimizing browsing damage from deer

Foothill residents and mule deer can easily coexist with some planning

When mule deer browse expensive nursery plants on foothill benches during the winter, they often destroy or reshape trees, shrubs and flowers. However, with proper planning, homeowners can assist wildlife and create attractive landscapes. Information in this article can help homeowners, nursery operators and landscape architects plan home landscapes that are compatible with plant utilization patterns of mule deer on winter ranges.

Preventing deer use

The most effective way to eliminate browsing by deer is to enclose the area with a fence that is at least 7.6 feet high. Entrances must be closed at all times, particularly at night. Lower fences, such as 4-foot-high chain-link, and decorative, wood or metal fences will reduce, but not eliminate use. Repellents such as systemic insecticides, human hair, soap and other chemicals, as well as outdoor lighting and artificial noise, are unreliable in preventing deer use.

Protective plant adaptations, such as thorns on rosebushes, are also generally ineffective. Hungry deer tend to ignore repellents and browse (graze) available plants. Individual plants that are highly susceptible to deer damage can be protected by thoroughly wrapping with burlap or several layers of plastic.

Extent of the deer winter range

Almost all foothill bench areas as well as many valley floors are traditional wintering and foraging areas for mule deer. For example, Old Main Hill on the Utah State University campus in Logan was once a rocky slope covered by big sagebrush, a primary winter food of mule deer. In the predawn hours, deer still browse cultivated ornamental plants that have replaced the native rangeland species.

During the day, deer usually stay in the thickest vegetative cover available and as far as possible from homes and people. At night. deer leave the security of daytime cover and venture out in search of forage. Plants around homes closest to good deer habitat, such as streamsides, brushy draws, juniper patches and Gambel oak stands, will generally be the most heavily browsed. Although deer use of landscaped plants usually decreases as distance to daytime cover increases, noticeable browsing often occurs within one mile of cover areas.

Factors affecting plant use by deer

Deer typically begin using traditional winter ranges, with or without housing developments, soon after the end of the deer hunt in early November. They eat the most preferred plants first, which may be the only plants browsed during mild winters. During severe winters almost all available plants are browsed to some degree. Deer usually continue browsing until spring green-up in March or April but can continue browsing until May or later when early spring flowers such as crocus and tulips are abundant.

The number of deer on the range alternate food sources, including native and urban foraging areas, winter weather conditions, and plant preferences, also influence the degree of plant use by deer. Browsing of ornamental plants typically increases after heavy snowfalls limit the mobility of deer. Deep snow forces deer to move to lower elevations where plants are more accessible.

Deep snow cover may also prevent deer from browsing low-growing and small ornamental plants. Deer will generally dig down through only about eight inches of snow to obtain forage. Snow depth must be deeper to protect taller plants. Mule deer generally browse no higher than six feet but can reach higher when standing on snow.

Browsing of landscaped plants is likely to increase during severe, long winters when snow cover is deep and extensive. As forage supplies dwindle, deer will reach higher and dig deeper for food. Plants in secluded locations tend to be more susceptible to browsing. The presence of household pets may discourage use.

Plant recovery from deer use

Many heavily browsed plants recover vigorously during spring and summer, especially when regularly watered, fertilized and weeded. Many native plants are ecologically adapted to annual moderate or heavy browsing. Winter browsing stimulates new vegetative growth in spring, even on dry rangelands.

Although regrowth of many ornamental plants may increase if browsed during the growing season, some do not recover from heavy winter use and others may require two or more growing seasons to recover. Two growing seasons are often required to replace the vegetative and fruiting buds of apple trees browsed during the winter. Evergreen conifers, junipers, pines, firs and spruces are the most susceptible plants to permanent damage by deer. In addition to direct browsing damage, occasionally heavy use exposes plant tissues and can lead to frost damage.

Observation of plant use

Deer use of ornamental plants was studied during the winters of 1979-81 in 12 landscaped yards on foothill benches near Layton and Bountiful, Utah. Utilization of all plant species in each yard was evaluated in late winter by estimating the proportion of the current annual growth removed by mule deer. Plant species were categorized by the degree of deer use: no use (0 percent), light (1-40 percent), moderate (41-70 percent) and heavy use (71+ percent).

The results of these and other observations were used to evaluate the likelihood that ornamental plants would be utilized by deer. The lists are not inclusive and should serve only as guidelines. Additional research is needed. Deer will probably exhibit similar preferences for related plants. The recommended list of native shrubs was based on the field, research and home landscaping experiences of the authors and reviewers. A similar list was developed using whitetailed deer in Connecticut.

Landscape planning on deer winter ranges

Ornamental plants, which may be expected to receive heavy use by deer and are often permanently damaged, should not be planted unless they are completely protected. These plants, although generally highly preferred by and useful to deer, are less likely to survive and more likely to acquire an unattractive appearance due to browsing. Deer will eat most ornamental plants, many of which can recover from moderate use during the spring and summer. Many homeowners are willing to trade the opportunity to view wildlife in backyards for moderate browsing.

Fortunately, some plants are seldom browsed by deer except during harsh weather when other forages are not available. Many of the native shrubs provide forage for mule deer on winter ranges and are also attractive for landscape purposes. Seeds and plant materials for some of these native shrubs may be available from commercial nurseries. The best sources are nurseries that specialize in native plants.

Small amounts of seeds for many species of native shrubs can be easily hand-collected in late summer through fall. Blending a variety of native and ornamental plants into a home landscape can create a highly attractive environment for people, mule deer and other wildlife species. Enhancing the home environment and replacing some of the lost wildlife habitat can be enjoyable and beneficial.

Ornamental plants highly preferred by mule deer

(These are generally not recommended for landscaping on deer winter range areas.)

Trees

Shrubs/small trees

Flowers/vines

Ornamental plants moderately preferred by mule deer

(These are generally recommended for landscaping on deer winter range areas.)

Trees

Shrubs/small trees

Flowers/vines

*Plant species native to Utah.

Ornamental plants seldom preferred by mule deer

(These are recommended for landscaping on deer winter range areas.)

Trees

Shrubs/small trees

Flowers/vines

*Plant species native to Utah.

Native shrubs used by deer in winter that generally recover during the growing season

(Most are also highly attractive to birds and other wildlife species.)