Shinsuke Koike

We investigated the foraging habits of the Asian black bear, probably the smallest bear population in the world, using 122 fecal samples, foraging signs, and stable isotope analysis of bear hair in Shikoku Island (SI). Fecal analysis revealed obvious seasonal changes, with the dominant food items being green vegetation in spring, soft masts in summer, and soft and hard masts in autumn. To clarify the characteristics of fecal content in SI, we compared it with that of bears in other areas of Japan. Although the fecal contents in the Pacific coastal area of the Kanto region were similar in several seasons, the bears may have been more dependent on animal matter from summer to autumn in SI. The analysis of feeding signs demonstrated that the bears consumed a wide variety of fruits of not only cool-temperate but also temperate-zone tree species. The stable isotope ratios of bear hair indicated similar diet to that of bears in their natural habitat on Honshu, suggesting little dependence on artificial food. Considering that only a few dozen bears are living in SI, it will be necessary to continue accumulating information on bear biology for conserving bears and their habitats in SI. Published online 15 September, 2026; Print publication 31 October, 2026

Human–bear conflict in Japan fluctuates markedly among years, often peaking following hard-mast failures that trigger large conflict years (LCYs) with intensified culling. How these spikes reshape population structure remains poorly quantified. We quantified age–structured dynamics of female Asian black bears Ursus thibetanus in central Japan and tested two predictions: (P1) older females are disproportionately affected during higher culling years; and (P2) increased culling pressure shifts age structure toward younger individuals. We implemented a two-step hierarchical framework model, estimating fecundity and natural mortality from independent data as informative priors for an age-at-harvest model fit to 17 years (2001–2017) of harvest records. We contrasted reconstructed dynamics with a counterfactual scenario of uniformly low culling and assessed these effects on age-classes. Culling rates increased with age (peaking at six to seven years old), and showed age-specific amplification during LCYs. Total abundance declined slightly (mean population growth rate = 0.984). High culling reduced the proportion of older age classes (≥7 years old) and also negatively affected cubs, yielding truncation of age structure rather than a clear rejuvenation. Conflict-driven surges of culling—on the order observed in LCYs—were sufficient to produce detectable demographic shifts via loss of mature females, without evidence of reproductive compensation. Adaptive monitoring should therefore track demographic indicators (e.g., proportion of reproductive-age females) and feed these back into quota setting to limit negative population effects.

A lack of information persists on external seed dispersal interactions, despite the rich diversity of potential dispersers. Roadkills offer a unique opportunity to obtain ecological data directly from carcasses. For 18 years, we collected road‐killed mammals in Toyama (Japan) and screened them for seed attachment. We then illustrated species interactions, quantified the number of plant species and seeds individual roadkill carried, and evaluated seasonal variations in the probability of seed attachment. We identified nine mammal species dispersing seeds from 16 distinct plant taxa. Most importantly, medium‐sized mammals (1.5–10.0 kg) accounted for approximately 88% of roadkill carrying seeds, with raccoon dogs Nyctereutes procyonoides dispersing the most seeds. Likely due to seed‐set phenology, we showed a significant increase in seed prevalence for roadkills occurring in autumn. We advocate for future studies in epizoochory to focus on potential animal dispersers community wide.

In male mammals, reproduction and reproductive behavior are strongly influenced by testosterone. While some species exhibit roaming behavior to encounter receptive females and show consorting behavior with females, the relationship between sex hormone and those behaviors remains unclear. To clarify testosterone's influence on behavior, we examined fecal testosterone metabolites (FTM) and behaviors in male Asian black bears ( Ursus thibetanus ) using collars equipped with GPS transmitters, activity sensors, and animal‐borne cameras. We assessed four behavioral variables (daily movement speed, net movement distance, turning angle, activity level) and mating behavior in five males over a cumulative 8 years. Fresh fecal samples, collected at GPS locations of collared individuals, were analyzed for FTM. In total, 111 feces were collected in 2022–2023 across 58 locations. The FTM values and the four behavioral variables were compared between the breeding (May–July) and post‐breeding season (August–November) using the Brunner–Munzel test. Overall, FTM were higher, while movement speed and activity levels were lower during the breeding season than in the post‐breeding season. These results suggest that some males may engage in consorting associated with elevated testosterone. We further examined the relationships between FTM and the four behavioral variables using Spearman's correlation tests. The correlation between FTM and behaviors varied among males. For example, the relationship between FTM and net movement distance was negative in two males but positive in three males. These interindividual differences in testosterone–behavior correlations were possibly the result of incomplete sampling during mating and consorting, as well as variation in breeding strategies. The negative relationships may indicate mate guarding or consorting, whereas positive relationships may reflect roaming. Our results suggested that the behavior of male Asian black bears may be influenced by increased testosterone, and monitoring testosterone allows us to gain insights into male bear behavior.

This study reviewed worldwide spatial patterns in the food habits of Asiatic black bears (ABB) in relation to geographical (altitude, latitude, and longitude) and environmental (climate type, rainfall, temperature, and vegetation type) variables. Data on the ABB diet were collected from 29 cases based on fecal analysis. Three seasonal data were separately analyzed using principal component analysis and linear regression models. During spring, green vegetation and hard mast were mainly characterized by high loadings; latitude had a significant relationship. During summer, green vegetation, soft mast, and invertebrates were mainly characterized by high loadings; altitude, latitude, longitude, precipitation, and temperature had significant relationships. During autumn, soft and hard masts were mainly characterized by high loadings; temperature and latitude had significant relationships. Spatial variation in the bear diet was the main result of vegetation types due to climatic factors that affect the nutritional and energetic requirements of bears and the availability of local food. In contrast, the tradeoff between food availability, nutritional conditions, and energetic requirements determined the food items. However, there were many distributions where dietary information was lacking, so accumulating information is essential to elucidate the ABB feeding strategy and how it adapts to each environment.

Sexually dimorphic ungulates often show differences in habitat use between sexes; however, information on seasonal changes in habitat use according to sex and the presence of offspring is scarce. This study aimed to clarify the seasonal differences in habitat use of sika deer ( Cervus nippon ) according to sex, age, and the presence of offspring in the highly seasonal habitats of the subalpine zone of Mount Fuji, Japan. Habitat use varied across seasons and substantial differences according to sex and the presence offspring were observed in summer. In summer, males frequently used habitats with abundant forage (forest edges). Conversely, while females without offspring frequently used habitats with abundant forage (forest edges) and safety (flat terrain), females with offspring preferred safer habitats (forest interior, areas far from mountain trails, and flat terrain) instead. These results revealed that males, females without fawns, and females with fawns prioritized food intake over safety, both food intake and safety, and safety, respectively. These patterns reflect differences in vulnerability to predation and in strategies to maximize reproductive success. The habitat use of females with fawns changed drastically from summer to autumn: in autumn, they prioritized not only safety but also food conditions, suggesting that their habitat use changed seasonally as vulnerability declined with fawn growth.

There is an urgent need to develop global observation networks to quantify biodiversity trends for evaluating achievements of targets of Kunming-Montreal Global Biodiversity Framework. Camera traps are a commonly used tool, with the potential to enhance global observation networks for monitoring wildlife population trends and has the capacity to constitute global observation networks by applying a unified sampling protocol. The Snapshot protocol is simple and easy for camera trapping which is applied in North America and Europe. However, there is no regional camera-trap network with the Snapshot protocol in Asia. We present the first dataset from a collaborative camera-trap survey using the Snapshot protocol in Japan conducted in 2023. We collected data at 90 locations across nine arrays for a total of 6162 trap-nights of survey effort. The total number of sequences with mammals and birds was 7967, including 20 mammal species and 23 avian species. Apart from humans, wild boar, sika deer and rodents were the most commonly observed taxa on the camera traps, covering 57.9% of all the animal individuals. We provide the dataset with a standard format of Wildlife Insights, but also with Camtrap DP 1.0 format. Our dataset can be used for a part of the global dataset for comparing relative abundances of wildlife and for a baseline of wildlife population trends in Japan. It can also used for training machine-learning models for automatic species identifications.

Large terrestrial mammals have generally declined due to human activity, but the recovery of some populations poses new issues for coexistence. Few studies to date have investigated drivers of this recovery and its impacts on human societies at the national scale. We assessed the process of range expansion of six species of large terrestrial mammals over approximately 40 years and its impacts on human society in Japan, one of the most rapidly depopulating countries. We found evidence that increased agricultural abandonment and decreased snowfall drove the range expansion of large terrestrial mammals. The range of all six species expanded from mountainous landscapes to those closer to human settlements, leading to an increase in conflicts that threaten people’s property and safety. We predict that accelerating depopulation and climate warming could lead to further range expansion of these species, and call for measures to mitigate conflicts and achieve coexistence with them.

While diverse animal species have been implicated in epizoochorous seed dispersal, studies specifically focused on bird‐mediated seed dispersal are scarce. We evaluated the potential contribution of two terrestrial birds, green pheasant ( Phasianus versicolor ) and Chinese bamboo partridge ( Bambusicola thoracicus ), to epizoochorous seed dispersal using a dummy‐based method. Furthermore, we compared the number of seeds attached to birds and mammals using data from a previous study conducted using the same method, site, and season. The results revealed 435 seeds of four herbaceous species ( Achyranthes bidentata , Hylodesmum podocarpum , Oplismenus undulatifolius , and Persicaria filiformis ) attached to two bird dummies. All seeds found on birds possessed adhesive appendages such as hooks, bristles, or viscous substances. In addition, the number of attached seeds does not exhibit significant differences between birds and mammals, irrespective of the season or plant species. Our findings provide the first documented evidence of epizoochorous seed dispersal by Phasianidae birds, highlighting the potential redundancy and complementarity between birds and mammals in mediating epizoochory.