Nolte, Dale L; Wagner, Kimberly K; Trent, Andy . 2003. Timber Damage by Black Bears: Approaches To Control the Problem. 0324 2832. Missoula, MT: U.S. Department of Agriculture, Forest Service, National Technology and Development Program. 10 p.
Describes alternative approaches to controlling the damage black bears cause during the spring when they strip bark to eat the newly formed wood underneath. One bear might strip as many as 70 trees in a day. The trees will be damaged and may be killed if the bark is stripped all the way around the tree, girdling it. Bears appear to strip the most vigorous trees, preferring stands that have been thinned, or those where urea fertilizer has been applied. Bears also appear to prefer trees with a high concentration of sugars relative to the concentration of terpenes. Pruning decreases the sugar-to-terpene ratio, reducing the likelihood that trees will be stripped by bears. Bears generally quit stripping trees once other foods become available during the late spring or early summer. One approach to reducing damage has been to provide supplemental feed (pellets resembling dog food) in stands being damaged by bears. In one study, damage was just one-fifth as much in stands with feeders as in stands without feeders. Killing bears in areas where trees are being stripped can also reduce damage. Other approaches, such as relocation, contraception or sterilization, or repellents, are not generally practical for protecting forest plantations.
Keywords: animal damage control, carbohydrates, fertilization, girdling, plantations, reforestation, repellents, silviculture, sugars, terpenes, thinning, Ursus americanus
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