Publications
Diel and monthly activity pattern of brown bears and sika deer in the Shiretoko Peninsula, Hokkaido, Japan
Brown bears and sika deer on Japan's Shiretoko Peninsula exhibit distinct diel activity patterns influenced by seasonal behaviors, reproductive motivations, and environmental factors. Unlike European brown bears, those in Shiretoko show a diurnal/crepuscular pattern, with increased activity during autumnal hyperphagia, particularly among adult females and sub-adults. Protected areas further enhance diurnality, suggesting human activities and competitive interactions play significant roles. Sika deer, meanwhile, maintain a crepuscular pattern with minimal variation across months or sex-age classes, though male activity peaks during the autumn copulation period. The study employed camera-trap surveys over five months in 2019, capturing 7,530 observations to analyze these patterns, offering critical insights for wildlife conservation and management.
Identifying effective tree planting schemes to restore forest carbon and biodiversity in Shiretoko National Park, Japan
Tree planting in Shiretoko National Park, Japan, can effectively restore both forest carbon and biodiversity when done with high density (2,500+ trees/ha) and species richness (>4 species), regardless of distance from natural seed sources. Simulation modeling revealed that such planting scenarios achieve over 50% of the restoration success of intact forests within 33 years for both goals. Conversely, low-species planting or reliance on distant natural regeneration significantly delays biodiversity recovery.
Dining from the coast to the summit: Salmon and pine nuts determine the summer body condition of female brown bears on the Shiretoko Peninsula
Female brown bears on the Shiretoko Peninsula experience seasonal fluctuations in body condition, primarily driven by their access to high-lipid pine nuts and high-protein salmon. A six-year study (2012–2018) found that while body condition declined until late August, it began to recover in September when salmon consumption peaked. Years with higher intake of both pine nuts and salmon saw earlier recovery in body condition. Additionally, females with offspring had poorer body condition than solitary ones, especially during low-salmon years. The research used scat analysis (2,079 samples) and photographic measurements (1,226 images from 12 bears) to quantify diet and body condition, revealing the critical role of these unique coastal and subalpine foods in bear survival and reproduction.
Incidence of Multiple Paternity and Inbreeding in High-Density Brown Bear Populations on the Shiretoko Peninsula, Hokkaido, Japan
A study on the Shiretoko Peninsula, Japan, reveals that approximately 15% of brown bear litters result from multiple paternity, comparable to rates observed in Scandinavian populations despite differences in population density and litter size. The research also identified low but notable instances of inbreeding, including cases involving father-daughter matings (2.7%), maternal half-siblings (0.5%), and paternal half-siblings (1.8%). No evidence was found for mother-son or full-sibling matings. These findings suggest that male-biased dispersal plays a crucial role in limiting close inbreeding, offering insights into the genetic dynamics of high-density brown bear populations. The study genotyped 837 individuals at 21 microsatellite loci and analyzed parentage across 70-82 litters to derive these conclusions.
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.
Adaptation to climate-change effects on fisheries in the Shiretoko World Natural Heritage area, Japan
Climate change is significantly impacting fisheries in the Shiretoko World Natural Heritage area, Japan, with observed effects including reduced seasonal sea ice and shifts in fishing grounds. The study highlights the need for integrated policy measures and cross-sector coordination to adapt to these changes, emphasizing the importance of large-scale marine ecosystem (LME) research and monitoring. It also suggests that cultural elements, such as those promoted by the World Heritage programme, could contribute to developing a new, peaceful societal framework based on LME principles.
Evaluation of nutrient flux from Shiretoko into the ocean using MRI-GCM
Researchers found that rainfall intensity, particularly its standard deviation, significantly controls nutrient flux from Shiretoko's inland areas to the coast. This discovery highlights a key factor influencing coastal ecological systems. To estimate future nutrient supply, the study used bias-corrected data from the Meteorological Research Institute Global Climate Model (MRI-GCM), which aligns well with observed rainfall data. A synthetic generation technique produced hourly rainfall data, crucial for assessing nutrient dynamics in Shiretoko's river basins. The findings suggest that nonlinearity in rainfall intensity strengthens its impact on nutrient flux, providing critical insights for understanding coastal nutrient cycles.
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