Elk and deer (two ungulate species) cause the most widespread damage to forest resources. Elk may trample or pull seedlings without well-established root systems out of the ground. Browsing elk often splinter woody stems. During the spring, the stems may be stripped of bark below where they break the stem. Deer damage inflicted on seedlings is similar to elk damage. Woody stems are often splintered and the bark is stripped from twigs. New buds are generally clipped back to the previous year's growth. Deer do not pull seedlings as frequently as elk and their damage rarely occurs above 6 feet.
Traditional frightening devices, as listed above, are generally ineffective to deter ungulates for prolonged periods. However, devices activated by an animal's presence are generally more effective than permanent or routine displays. Further, a device affixed to an individual animal may generate responses from those individuals, and possibly from accompanying animals of the same species (conspecifics). For example, a device affixed to a matriarch elk that activates a signal (e.g., strobe and siren) and after a couple seconds delivers a mild shock to the matriarch may be very effective in inhibiting this animal from remaining in a protected site. Accompanying conspecifics pairing these signals with distress displayed by their leader also may avoid the area.
Electric collars and ear tags have shown promise for deterring cattle from protected areas, such as riparian zones. Although effective, current technology prohibits operational use of these devices to deter deer and elk from target areas. Technology more applicable for prolonged use with these animals is being pursued by field station scientists.
An improved understanding of deer and elk foraging ecology may help to reduce browsing on establishing seedlings. All plants contain toxins, and the amount of toxin an animal can ingest depends on the kinds and amounts of nutrients and toxins in the forage. Field station researchers are trying to determine if nutritional status of deer and elk affects their preference for Douglas-fir seedlings. Supplemental energy and protein increases the ability of animals to eat foods that contain toxins. Thus, supplemental nutrients offer the potential to increase intake of plants habitually avoided or to decrease intake of plants habitually eaten. Other, studies are investigating potential to select for western red cedar genotypes that may be less preferred by deer because of high terpene concentrations.
Field station biologists are also working to identify feasible approaches to exclude animals from sites. Alternative fence designs have been investigated. In addition, scientists at the station routinely evaluate efficacy of marketed repellents. Concurrently, scientists are conducting parallel behavioral and chemical assays to identify potential natural aversive agents for new repellents.