Home ranges and habitat use of Asiatic black bears in Nagano Prefecture, Japan

Japan may have >20% of the world's Asiatic black bears (Ursus thibetanus), but continuing local extinctions have resulted in an overall decrease of the Japanese subspecies (U. t. japonicus). This decrease is related to loss and fragmentation of habitat and liberal permit systems for depredation kills. Science-based management could mitigate much of the effects of these threats, but decisions usually are made without adequate ecological data. From 1997 to 1999, I studied bear habitat relationships in the central, mountainous region of Honshu, the main island of Japan. Bears were captured with barrel traps and fitted with radiocollars. I collected 1,479 locations and selected 507 locations of 13 bears for analysis. Home ranges averaged 18.7 km² by the minimum convex polygon method; 10.0 km² for females and 24.2 km² for males. The average home range sizes for the 95%, 75%, and 50% contours were 24.2 km² (SD = 15.1), 20.4 km² (SD = 7.4), and 8.4 km² (SD = 3.2), respectively. I used classification and regression tree analysis (CART) to determine the hierarchical structure of bear-habitat associations in a 154-km² study area. I generated random locations within the study area and compared habitat types with those of bear locations. Bears used oak and planted forests in the montane zone (<1,460 m) more than expected. Habitat use at this local scale seems mostly related to the distribution of food resources, such as hard mast in the natural oak forests and soft mast in the planted forests. I also applied a model of habitat use based on the Mahalanobis distance statistic to a 432-km² area. Areas with the greatest bear use were usually associated with deciduous forests, of which >95% had oaks as 1 of 2 dominant species. The model associated values for lower habitat quality with cut forests that had poor regeneration. Cut areas that were regenerated through planting often had higher values in the model; these areas may be used for cover or for food resources, such as soft mast. Where bears included low-quality habitat in the core of their home ranges, they also had access to higher quality habitat. The results of this study indicate that different forestry management schemes influence bear habitat use. The most critical management needed to ensure the long-term viability of the Asiatic black bear population in Japan is the protection and promotion of oak-dominated forests in the montane zone.