Over 1,000 Asiatic black bears (Ursus thibetanus) are killed each year in Japan to control depredation activity. Our objective was to determine if killing bears reduces depredation costs. We focused our study on Nagano Prefecture, where 2,562 nuisance bears were reported killed and where reported depredation cost exceeded ¥1,430 million between 1979 and 1999. We used mixed models with repeated measures to determine if annual depredation costs were associated with the number of bears killed. Our data set included 15 years (1985–99) of kill and cost data for 122 municipal jurisdictions within 10 regions. We performed analyses at the regional level based on combined harvest and nuisance kill data, and at the municipal level based only on nuisance kill data. We classified the number of kills into 3 classes (low, medium, high). Analyses were repeated using prior-year kills to examine whether a possible time-lag existed. Annual depredation costs were positively associated with the kill data at the regional level (F = 5.51; 2, 72.3 df; P = 0.006) during the same year. However, we observed no association based on prior-year kill data (F = 0.96; 2, 65.1 df; P = 0.390), suggesting that depredation costs and bear kills are a function of nuisance bear numbers rather than reflecting a causal relationship between the 2 measures. Nuisance bear numbers may in turn be affected either by the availability of natural foods or by general population trends. At the municipal level, depredation costs were not associated with the number of nuisance bears killed during the same year (F = 1.36; 2, 466 df; P = 0.258) or the prior year (F = 0.42; 2, 459 df; P = 0.656). Our results suggest that systematically killing Asiatic bears may not be an effective tool for mitigating nuisance costs. In municipalities where nuisance costs remain high, we recommend that alternative methods be tested for their efficacy in mitigating costs. Such methods may include public education, changing or removing financial incentives to kill bears, changing crop rotations to crops that are not attractive to bears in risk areas, promoting natural food production, using electric fences, and applying aversive conditioning techniques.
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Vol. 15 • No. 2