Across the world, large carnivores are increasingly encountered near towns, farms, and schools. Understanding which age classes are represented in conflict-related removals can inform both ecological interpretation and management. In northern Nagano, Japan, Asian black bears (Ursus thibetanus japonicus) are often captured after repeated sightings near residential areas. The Hokushin region combines high bear density with steep mountains closely interwoven with settlements, creating frequent opportunities for human–bear encounters and subsequent capture responses.
Here we characterize the age profile of bears captured in peri-urban contexts over the past 20 years and evaluate how this profile has changed in association with topographic and land-use conditions. Ages were estimated using cementum annuli analysis of extracted premolars. We analyzed estimated age with generalized linear mixed models including elevation, slope, topographic position (valley, ridge, hillside), surrounding land use (forest, farmland, orchards, settlement proximity), and time period, and tested interactions between landscape variables and time to assess temporal changes in associations. Importantly, our results describe bears removed following encounter-based management and therefore reflect the intersection of bear space use, human reporting, and capture practices.
In the middle 2000s, bears captured on gentle slopes adjacent to farmland were predominantly younger than 10 years, consistent with the idea that dispersing juveniles are more likely to appear in accessible peri-urban settings. Older individuals were more frequently captured in steep, high-elevation areas. Over time, however, the mean age of bears captured within agricultural mosaic landscapes increased, and older individuals—including bears in their late twenties—were increasingly recorded in similar peri-urban environments.
These patterns suggest that the demographic profile of encounter-triggered captures has shifted over time, implying changes in how multiple age classes interact with human-modified landscapes. Rather than indicating population-wide aging per se, because captured individuals are not a random sample of the population, our findings point to a changing composition of bears involved in peri-urban encounters, potentially driven by shifts in landscape resource availability, bear behavior, and/or management response. More broadly, our results highlight how interactions between population structure and landscape configuration can reshape patterns of human–wildlife conflict, a challenge faced by many regions undergoing simultaneous wildlife recovery and landscape intensification.