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Open Access Publications from the University of California

Efficacy of black bear supplemental feeding to reduce conifer damage in western Washington

  • Author(s): Ziegltrum, Georg J.
  • et al.

While searching for food, one black bear may girdle 60 - 70 coniferous trees in a day during the spring months in western Washington. Tree-bark peeling and subsequent foraging on sapwood can result in substantial economic losses for forest landowners. The supplemental feeding program, a nonlethal approach to minimize black bear damage by providing an alternative food source, was developed by the Washington Forest Protection Association in 1986. From 1998 to 2002, I studied the efficacy of this supplemental feeding program on the Olympic Peninsula. I selected 14 conifer stands of approximately 20 ha each for study. Mean pretreatment conifer damage on these sites in 1998 was 26% of trees. In March 1999, 1,000 trees were marked on 4 transects throughout each stand. Two feeding stations were installed on each of 7 randomly chosen stands in April of 1999, while no supplemental feed was supplied on the remaining 7 control stands. I found that bears damaged significantly more trees on control sites than on treatment sites (P < 0.001). To validate initial results, I removed feeding stations from 2 of the 7 feeding sites in July 2000. Damage increased by a factor of nearly 7 on one feeding site over the next 2 years. I concluded that the supplemental bear feeding program constituted a viable, nonlethal damage control tool.

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