Reproductive parameters and cub survival of brown bears in the Rusha area of the Shiretoko Peninsula, Hokkaido, Japan

Brown bears (Ursus arctos yesoensis) in the Rusha area of Shiretoko, Hokkaido, Japan, exhibit among the highest reproductive rates globally, with females producing 0.70 to 0.76 young per year. A long-term study (2006–2016) tracking 15 philopatric females revealed key parameters: mean age of first reproduction at 5.3 years, litter sizes averaging 1.76 cubs, and inter-birth intervals of 2.43 to 2.53 years. Cub survival rates (60–73%) peaked in mortality during summer (July–August), likely due to nutritional stress. These findings align with global trends but highlight Shiretoko's unique demographic dynamics, offering critical insights for conservation strategies.

Shimozuru, M., Yamanaka, M., Nakanishi, M., Moriwaki, J., Mori, F., Tsujino, M., Shirane, Y., Ishinazaka, T., Kasai, S., Nose, T., Masuda, Y., & Tsubota, T. (2017). Reproductive parameters and cub survival of brown bears in the Rusha area of the Shiretoko Peninsula, Hokkaido, Japan. Plos One, 12(4), e0176251. https://doi.org/10.1371/journal.pone.0176251