Estimation of the Number of Nuisance Bears in the Oshima Peninsula, Hokkaido

ABSTRACT In Hokkaido, Japan, various management measures are being implemented to mitigate human‐brown bear conflicts. To evaluate the effectiveness of these measures, we aimed to estimate the number of nuisance bears as an indicator of conflict based on damage and occurrence reports. For the estimation, we assessed the harmfulness level (Conditions 0–3) of the bears based on information provided in the reports and developed a method to remove duplicate or substantial overcounts of a bear resulting from multiple reports on the same individual. The specified criteria based on the difference in dates and distance were established to identify a single bear associated with multiple reports. By establishing two sets of criteria, one relaxed and one stringent, we estimated the minimum and maximum numbers of nuisance bears. We estimated the number of nuisance individuals annually based on the reports collected from 2009 to 2023 in the Oshima Peninsula, Hokkaido. The total number of nuisance individuals fluctuated between 362 and 495 (maximum) and 163 and 214 (minimum) in the first half of the 2010s. Thereafter, the maximum number of individuals in Condition 0/1 (lower harmfulness) continued to increase, reaching 504 in 2023, whereas the number of individuals in Conditions 2 and 3 remained relatively stable, ranging from 153 in 2015 to 261 in 2018. Establishing a specific criterion to estimate the number of nuisance individuals involved in conflict provides a more valuable evaluation indicator for adaptive management than one that solely relies on the number of occurrences.