Male reproductive input, breeding tenure, and turnover in high-density brown bear (Ursus arctos yesoensis) populations on the Shiretoko Peninsula, Hokkaido, Japan

A high-density brown bear population on Japan's Shiretoko Peninsula shows relatively even male reproductive input, with 19 males siring 82 offspring from 54 litters over a decade. Paternity analysis using microsatellite DNA revealed that while some years favored certain individuals, breeding tenure typically lasted 1 to 6 years. Human-caused mortality in peripheral areas disrupted this balance, highlighting the impact of human activity even within protected zones. Male reproductive success peaked at ages 10–14, aligning with physical maturity. These insights advance understanding of solitary mammal breeding systems and inform conservation strategies for vulnerable populations.

Shimozuru, M., Shirane, Y., Jimbo, M., Yamanaka, M., Nakanishi, M., Ishinazaka, T., Kasai, S., Nose, T., Fujimoto, Y., Tsuruga, H., Mano, T., & Tsubota, T. (2020). Male reproductive input, breeding tenure, and turnover in high-density brown bear (Ursus arctos yesoensis) populations on the Shiretoko Peninsula, Hokkaido, Japan. Canadian Journal of Zoology, 98(3), 175–185. https://doi.org/10.1139/cjz-2019-0061