Using DNA metabarcoding, we examined dietary components of the wild boar (Sus scrofa) and tested a common but rarely examined assumption that a small fecal subsample represents the dietary signal of an entire fecal mass. We analyzed multiple subsamples taken from the same fecal mass as well as already separated fecal pieces collected on Shodoshima Island, Japan, in May, July, and September, using chloroplast trnL and mitochondrial COI markers to infer plant and animal dietary taxa, respectively. Relative read abundance data revealed substantial variation in both plant and animal dietary taxa among subsamples originating from feces of the same individual. These results indicate that extracting DNA from a small, arbitrarily chosen portion of feces can lead to biased or incomplete dietary inference, and highlight the methodological importance of sufficient homogenization of as large an amount of fecal material as possible in DNA metabarcoding studies of wild boars and other large mammals. In addition, our approach recovered seasonal dietary patterns consistent with previous studies and enabled genus-level identification of several animal taxa, including earthworms (Amynthas and Metaphire) and centipedes (Scolopendra and Scolopocryptops), as well as previously unreported plant taxa such as Platycarya and Rhododendron.
Recently, the distribution of sika deer has expanded, and their high densities have caused damage to agriculture and forestry and adversely affected natural vegetation. Appropriate population management is necessary to reduce damage and mitigate adverse impacts on ecosystems. Understanding the habitat selection of sika deer is essential for more effective management. The objectives of this study were 1) to evaluate the habitat selection of sika deer and 2) to predict suitable habitats in summer and winter. We analyzed the data by resource selection function (RSF) model, using GPS data from two adult females tracked from June 2021 to August 2023. We used the presence or absence of deer use as the objective variable and environmental factors (weather, topography, vegetation, distance to forest edge, etc.) of the study site as explanatory variables. The results indicated that sika deer selected deciduous broad-leaved forests and grassland with gentle slopes close to the forest edge in summer and south-facing slopes at lower elevations in winter. The RSF values were then used to create a predictive map of potential habitat suitability for the entire region. Our findings will contribute to population management for sika deer to maintain low density in expanding distribution areas. Published online 28 April, 2026; Print publication 31 July, 2026
（要旨）． アカボウクジラ科鯨類 3 種における陰茎および関係する生殖器構造の形態学的研究． アカボウクジラ科鯨類は，種間および雌雄間で高い形態的多様性を有しており，性選択が種分化を促進する重要な要因である可能性が示唆されている．しかしながら，アカボウクジラ科鯨類の生殖器に関する知見は限られている．本研究では，漁業および死亡漂着によって得られたアカボウクジラ科鯨類に属する，ツチクジラ，アカボウクジラ，タイヘイヨウアカボウモドキの 3 種の雄性生殖器構造を解剖学的および組織学的に調べた．基本的な生殖器の構造は 3 種間で共通しており，これらは他のハクジラ類と同様の形態学的特徴を有していた．3 種とも陰茎は円錐形で，共通の内部構造を有していたが，一部のハクジラ類で報告されている尿道突起に類似した陰茎伸長部といった特徴的な構造は認められなかった．アカボウクジラの前立腺および前立腺圧迫筋は極めて小さく，ツチクジラにおいても同様の筋構造と痕跡的な前立腺様組織が認められた．タイヘイヨウアカボウモドキでは組織の劣化のため前立腺は特定できなかったが，他のハクジラ類で認められるような発達した前立腺圧迫筋は認められなかった．本研究で得られた知見は，知見が少ないアカボウクジラ科鯨類の繁殖生態の理解に貢献する貴重な知見を提供するものである．
The waters around the Chichijima Islands of the Ogasawara Islands, approximately 1000 km south of mainland Japan, are known breeding areas for humpback whales Megaptera novaeangliae, although their suitable habitat in this area has not been assessed in a spatially explicit manner. This study examined the relationship between the spatial distribution of humpback whales and topographic factors, using boat-based sighting survey data from 2013 and 2015–2018. A generalized additive model (GAM) and a maximum entropy model (Maxent) were used to estimate the suitable habitat of humpback whales. Both models demonstrated that the whale distribution was related to water depth and seabed slope, with water depth having a particularly strong influence. High suitability was observed at shallow water depths and gentle slopes, reaching a maximum at depths of 50–60 m and slopes of 0.5–0.8°. Additionally, suitable habitats were more extensive off the west coast than off the east coast, suggesting that the western area was more suitable for whales. The resulting habitat suitability map provides valuable information about their key habitats and can be utilized for their appropriate conservation in this area. Published online 18 May, 2026; Print publication 31 July, 2026
