Abstract
The relationship between the acorn crops of trees belonging to the Fagaceae family and the mass intrusion of Asiatic black bears (Ursus thibetanus) into the residential areas of the Hokuriku region were investigated based on an acorn crop monitoring survey conducted over a 7-year period, from 2005 to 2011, in the Toyama, Ishikawa, and Fukui Prefectures of Japan. Large fluctuations were observed in the annual acorn production of both Fagus crenata and Quercus crispula located in the high-altitude areas of all three prefectures. In particular, extremely poor yields of acorns were noted for 2006 and 2010, which coincided with the mass intrusion of bears into the residential areas. In contrast, little fluctuation was observed in the annual acorn production of Q. serrata distributed in low-altitude areas, and there were no incidents of years with extremely poor yields. These results infer that food shortages, due to simultaneous poor crops of F. crenata and Q. crispula in the mountainous areas of Hokuriku region, triggered the mass intrusions of bears into residential areas. Since the fluctuations in the annual acorn production of these key species were synchronized across a wide geographic area, a comparative analysis and coordinated survey of the acorn crop monitoring of each neighboring prefecture should result in an effective as well as accurate forecast of the acorn yields and therefore of bear intrusions.
