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Timber Damage by Black Bears:
Approaches to Control the Problem

Table 1—Douglas-fir trees damaged by black bears on seven 20-hectare timber stands with feeders and seven 20-hectare timber stands without feeders.

Table 2—Douglas-fir trees damaged by black bears on seven 20-hectare timber stands with feeders and seven 20-hectare timber stands without feeders the second year after the feeders were installed.

Nutritional consequences—During the spring, bears living in areas with feeders gained more weight than bears in areas without feeders. By the fall, bears of the same age had the same weight whether they lived in areas with feeders or not. Therefore, feeding probably does not improve the reproductive fitness of bears. The study did not assess whether the program benefited lactating females. However, the high-energy diet in areas with feeders may enhance a female bear’s milk production, improving the chance her cubs will survive.

Behavioral consequences—Bear behavior around the feeders was monitored. All classes of bears fed at the stations (table 3). There was no indication that one class of bears (such as females) avoided feeders during times of high use more than another class of bears (such as large males). Most bears visited more than one feeder. Bears generally fed at feeders every 2 or 3 days. No bears were observed protecting feeders from intruders. Dominant bears may not restrict access to this resource because feeders provide an unlimited amount of food. Radio telemetry studies showed that the presence of feeders did not affect the size of a bear’s home range.

The use of feeding stations requires a long-term commitment and should be continued until trees are old enough that the risk of damage is reduced. Some bears may not eat from the feeding stations and may continue to damage trees. Lethal control may have to be combined with feeding stations before damage is reduced to acceptable levels.

Table 3 —Type and number of black bears monitored at feeders in western Washington during 1999 and in western Oregon and Washington during 2000.

Alternative Approaches

When bears are damaging valuable trees, a manager needs to develop a damage management strategy that considers all feasible approaches to resolve the problem and selects the most appropriate approach for each situation. Many approaches other than supplemental feeding have been suggested by persons with little or no experience in protecting forest resources. Although most of these suggestions lack merit, they should be considered. Under some conditions, it might be feasible to adapt some aspects of them into a comprehensive management strategy.

Conditioned avoidance—Conditioned food avoidance occurs when a food is altered to produce gastrointestinal distress. Generally, animals are more likely to form aversions to novel foods than to known “safe” foods. Training animals to avoid safe foods requires repeatedly feeding them altered food that produces gastrointestinal distress. When bears peel trees, they are eating a known source of sugars when other sources are limited. Using conditioned aversion to train bears to avoid sapwood is impractical.

Fencing—Excluding animals from a site prevents them from causing damage. However, constructing and maintaining a fence that will keep bears out of forest stands would be costly, particularly in areas with steep terrain. Regardless of the cost, a fence would impede movements by other wildlife, pose a hazard to some species (such as deer), and require disturbing natural habitats during installation. Fencing can be used to protect small research plots or valuable genetic sources from bears, but fencing is not a practical approach to prevent damage at most sites.

Birth control—Some persons have proposed managing black bear populations through contraceptives or chemical sterilants. If conception were prevented in enough females, local populations would decline over the long term. The efficacy of this approach and the ethical concerns associated with it remain controversial among biologists and the general public. Although this approach is occasionally promoted by some individuals or groups, no chemical or biological contraceptive agents are available for use in bears.

Devices to frighten bears—Devices traditionally used to frighten animals, such as propane cannons, sirens, lights, and scarecrows, are generally ineffective, even over the short term. The effect of these devices on bears has not been studied. Bears generally avoid human activity. Lights or noisemakers can deter bears, but bears will become accustomed (habituated) to these devices over time.

Devices activated by an animal’s presence are generally more effective than permanent or routine displays. These devices will probably deter bears longer than devices that are active whether or not a bear is present. Installing devices on the scale needed to deter bears from a forest plantation would be costly because the entire plantation would have to be covered. Forest plantations provide habitats and resources for numerous wildlife species that would be harmed if the devices were truly effective. The ecological implications of treating thousands of forest hectares with sirens and lights would probably prevent their use. These devices are generally impractical, except to protect small, carefully selected areas. Repellents—Repellents reduce the desirability of a food. Bears avoid apples treated with bittering agents. Several commercially available deer repellents contain bittering agents. A study assessing whether repellents could prevent bears from stripping trees was inconclusive, but results indicated that additional research was merited. If repellents are applied across a plantation, bears may have to choose between going hungry in the spring or eating a nutritious, but bitter, food. Bears might move to untreated areas. But the practicality and cost of treating thousands of trees each spring will probably prevent repellents from being used, except to protect small, carefully selected stands.

Alternative natural plants—Bears are believed to peel trees because other forage is limited or of poor quality. Bear damage occurs during the spring when most plants are dormant or are too small to provide much nutrition. Landowners can encourage plants that are available during the spring, such as skunk cabbage and devil’s club. Salmon berry produces a berry crop earlier than most plants. Alternative plants should have sugar levels that are higher than tree sap to deter bears from stripping trees. These plants are unlikely to provide enough food to maintain bears throughout the spring. In addition, if these plants were encouraged near a vulnerable timber stand, they might attract bears to the stand.

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