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Timber
Damage by Black Bears:
Approaches to Control the Problem
Three primary options are available to reduce bear damage:
The appropriate approach depends on management objectives and site characteristics. A damage management plan may incorporate more than one of the approaches. Other nonlethal approaches (such as devices to frighten bears, fences, or repellents) can be considered, but are generally impractical for large forest stands.
Historically, bears were killed to protect timber resources from bear damage. Animal damage control agents or professional hunters were hired to trap and hunt bears in areas where damage was occurring. Although regulations governing control measures have changed, professional agents are still effective in removing problem animals. Aldrich foot snares permit agents to target bears in specific areas. Trained hounds also can be used to locate problem bears. Depredation hunts may be used to remove problem animals.
Recreational hunting can be used to suppress bear populations. Special bear hunts have been authorized in some high-damage areas. Hunters can be encouraged to hunt in areas where tree stands are most vulnerable to bear damage. In such cases, maps of specific bear-damage areas can assist sport hunters. Master hunter programs provide additional training for hunters. Graduates of such programs provide a pool of ethical and knowledgeable hunters for use in sensitive damage-control situations such as these.
The general public would often prefer that bears be moved rather than killed. Moving bears is generally impractical. Few, if any, unoccupied favorable sites exist where bears will not cause similar problems. Furthermore, once bears have learned to strip trees, moving the bears may move the problem. Even after bears have been moved, they are likely to return to their original capture site. Bears that are relocated may transport diseases or parasites to other bear populations.
Bears are selective when choosing the areas where they forage and the trees they strip. Several trees within a stand may be stripped while adjacent trees are ignored or barely damaged. Bears select the healthiest, fastest growing trees. Damage occurs more frequently after certain silvicultural practices. Thinned stands tend to be more vulnerable than dense stands. Depredation also appears to increase after urea fertilizer has been applied.
A series of studies was conducted to assess whether bears selected trees to strip based on chemical constituents within a tree’s vascular tissue and the impact of forest management practices on these constituents. Sugars and terpenes were correlated with the extent of damage inflicted on a tree. Generally, sugars are desirable to bears and terpenes are not. Sugars are concentrated in the vascular tissue of trees. Conifers have high concentrations of terpenes, compounds known to discourage animals from feeding on other plants. A summary of the test results include:
Silvicultural practices affect chemical constituents found in trees. The extent to which altering practices to reduce bear damage depends largely on alternative foraging options. For example, a pruned stand located among unpruned stands may be less vulnerable to bear damage, but if all stands are pruned, the bears’ options become limited to ingesting fewer carbohydrates or going hungry. Given this option animals generally do not select starvation. Greatest value of understanding the impacts of silvicultural practices may be predicting where and when bear damage is likely to occur and appropriately implementing management techniques.
Private timber managers began investigating alternative damage control techniques during the mid-1980s. In 1985, bears were provided an alternative food source to reduce tree girdling. During the first year, about 2,250 kilograms of pellets were fed to bears from 10 feeders. Since its inception, this program has continued to grow. During 2001, about 300 metric tons of pellets were offered from about 900 feeders across western Washington, and a few feeders in California and Oregon.
Feeding Stations—Most forest managers in western Washington use similar approaches when feeding bears. Feeding stations (figure 3) are constructed from 55-gallon (250-liter) metal or plastic drums. An opening in the front provides access to pellets. A simple self-feeding delivery system prevents bears from spilling pellets. A foam-insulated plywood roof keeps pellets dry. A single feeder holds about 90 kilograms of pellets. Commercial pellets are about 0.6 centimeter in diameter and 1.3 centimeters long. They resemble dry commercial dog food, but are greenish. The sugar concentration in pellets is high (about 20 percent) and provides at least four times the concentration of sugar found in the vascular tissue of Douglas-fir trees during the spring. The pellets include fats, proteins, vitamins, and minerals to provide the bears a nutritionally balanced diet. Feeders normally are placed near a road so they can be restocked easily, but away from public areas to avoid possible conflicts with people. All feeders are removed from the forest at the end of the feeding season, sometime during the middle of July. Bears normally wean themselves from feeders once alternative foods (such as berries) become available. When feeding stations are no longer being used, they are removed to reduce vandalism and the perception that feeders could serve as bait stations for persons hunting bears.
Figure 3—A feeding station that dispenses pellets with a high
concentration of sugar. When they had the opportunity, bears
tended to feed on pellets rather than strip bark from trees.
The supplemental feeding program appeared to be effective in reducing bear damage in particular timber stands. Bears generally girdle fewer trees after they start consuming pellets. However, limited empirical evidence was available to document these observations. In addition, the effect of supplemental feeding on bear behavior is largely unknown. Several studies were conducted to learn more about supplemental feeding and its effects. Summaries of the results of those studies follow.
Efficacy—Overall, supplemental feeding reduced damage to Douglas-fir trees. Damage in stands with supplemental feeders was just one-fifth the damage in stands without feeders during the first year pellets were offered to bears (table 1). In most feeding sites, damage was even less severe during the second year (table 2). Bears probably require time to locate feeders and begin using them.
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