Shiretoko Museum

Understanding the interactions among hosts, vectors, and pathogens is essential for elucidating the ecology of tick-borne diseases. However, studies on tick fauna and pathogenic infections in large mammals in Hokkaido, Japan remain limited. We examined the spatial and temporal (region and season) and host factors (sex and age) affecting pathogen prevalence and tick infestation in sika deer (Cervus nippon yesoensis) and brown bears (Ursus arctos yesoensis) in Hokkaido. We selected Anaplasma and Hepatozoon, two prevalent pathogens in sika deer and brown bears, respectively, to analyze host-vector-pathogen relationships. Between 2021 and 2024, we tested samples from 223 deer and 437 bears for these pathogens and examined tick infestation patterns in 157 deer and 255 bears across four regions. Anaplasma infection prevalence was high in deer from South and East Hokkaido but low in those from North Hokkaido. Hepatozoon infection in bears was high in South and Central Hokkaido, and low in the East and North. Generalized linear mixed models (GLMMs) indicated that Anaplasma prevalence was determined by regional factors, whereas Hepatozoon infection was influenced by region and host age, with adults showing lower infection rates. Six tick species were identified: Ixodes ovatus, Ixodes persulcatus, Haemaphysalis japonica, Haemaphysalis megaspinosa, Haemaphysalis flava, and Haemaphysalis longicornis. The GLMMs revealed that I. ovatus was more prevalent on male deer than females. Conversely, I. persulcatus nymphs were less prevalent male bears than females. Older hosts showed higher levels of infestation across multiple tick species. These findings reveal the complex interplay shaping tick-borne disease ecology in wildlife.

Abstract Information on age is essential for exploring the life history, conservation, and management of wildlife. Recently, DNA methylation levels-based methods using blood or skin have been established as alternatives to the traditional tooth-based method in bear species. However, the collection of these tissues is limited to captured or dead individuals. In the present study, we established the first hair-based age estimation model based on DNA methylation levels in brown bears, aiming for future application to less-invasively obtained hair of wild individuals. We performed bisulfite pyrosequencing and measured the methylation levels of hair root DNA. The methylation levels of cytosine-phosphate-guanine sites adjacent to the genes VGF, KCNK12, and ELOVL2 were found to be correlated with age. The best age estimation model used three cytosine-phosphate-guanine sites adjacent to two genes, VGF and KCNK12, with a mean absolute error of 3.2 years and median absolute error of 2.2 years after leave-one-out cross-validation. Our method is innovative because of the simplicity of sampling and the lack of requirement to capture bears. If this method can be widely applied to hair samples obtained in the field, the age structure of wild populations can be understood, contributing to ecological research, conservation, and management of bear species.

This study examined the parasite fauna of wild brown bears and differences in the likelihood of parasite detection by season (summer vs autumn), year, and host factors (sex and age class). From June 2022 to November 2024, 334 fecal samples were collected from the Shiretoko Peninsula, Hokkaido, Japan, and examined for parasites using the centrifugal flotation technique. Fecal DNA analysis and data from a long-term field monitoring survey led to the identification of 49 individuals, which were further classified based on sex and age. Parasites detected in the feces included Uncinaria sp. (35.0% of total samples), Baylisascaris transfuga (13.5%), Dibothriocephalus nihonkaiensis (8.4%), Strongylida (2.7%), Capillariidae (0.6%), and coccidia (0.6%). The prevalence of detection for D. nihonkaiensis tended to be higher in autumn (September-November) than in summer (May-August). The likelihood of B. transfuga and Uncinaria sp. detection varied by season, year, and bear age class. The likelihood of B. transfuga detection was significantly higher in autumn than in summer, and tended to be higher in young bears (0-2 years) than in subadult/adult (≥3 years) bears, whereas that of Uncinaria sp. was significantly higher in summer than in autumn and in subadult/adult than in young bears. Egg shedding by these three parasites tended to disappear before or during hibernation. These results suggest that the likelihood of parasite detection in brown bear reflects the interactions of environmental and host factors, including seasonal and/or annual changes in diet, winter hibernation, and host growth.

Ticks prefer specific feeding sites on a host that are influenced by host–tick and tick–tick interactions. This study focused on the spatiotemporal distribution of ticks in Hokkaido sika deer, an important tick host in Hokkaido, Japan. Tick sampling was performed on the sika deer in the Shiretoko National Park between June and October 2022. Ticks were collected from 9 different body parts of the deer to compare their attachment site preferences. Interspecific and intraspecific relationships among ticks were examined using co-occurrence analysis. The collected ticks were nymphal and adult stages of 4 species: Ixodes ovatus, Ixodes persulcatus, Haemaphysalis japonica and Haemaphysalis megaspinosa. Seasonal variations in tick burden were observed, with I. persulcatus and I. ovatus peaking in June and declining towards October; H. japonica showing low numbers in July and August and increasing from September; and H. megaspinosa appearing from September onwards with little variation. Attachment site preferences varied among species, with a significant preference for the pinna in I. ovatus and I. persulcatus. Haemaphysalis japonica was mainly found on the body and legs between June and August, and shifted to the pinna from September. Haemaphysalis megaspinosa showed a general preference for areas other than the legs. Co-occurrence analysis revealed positive, negative and random co-occurrence patterns among the tick species. Ticks of the same genus and species exhibited positive co-occurrence patterns; I. ovatus showed negative co-occurrence patterns with Haemaphysalis spp. This study revealed the unique attachment site preferences and distinct seasonal distributions of tick species in the Hokkaido sika deer.

2015年9月北海道斜里町で捕獲されたエゾヒグマを剖検したところ小腸より大型の条虫を検出した。頭節の形態および生殖器の配置から，Dibothriocephalus属と思われた。虫体の一部からDNAを抽出し，核28S ribosomal RNA geneおよびミトコンドリアcytochrome c oxidase geneの一部を解析した。その結果，DNAデータベース上の日本海裂頭条虫のものとほぼ一致し，本種を日本海裂頭条虫と同定した。本症例は，エゾヒグマから検出された条虫を日本海裂頭条虫と同定した初めての報告である。

Abstract Natal dispersal likely plays an important role in avoiding inbreeding among large carnivores. We tested the hypothesis that male-biased dispersal reduces close inbreeding by limiting the spatial overlap of opposite-sex pairs of close relatives in brown bears (Ursus arctos) in the Shiretoko Peninsula, Hokkaido, Japan. We genotyped 837 individuals collected in 1998–2017 at 21 microsatellite loci and performed parentage analysis. To calculate natal dispersal distance, we considered the site where the mother was identified as the birthplace of her offspring, and the site where the offspring were identified as their dispersed place. As predicted, we found that dispersal distances were significantly greater for males (12.4 km ± 1.0) than for females (7.7 km ± 0.9), and those for males increased from 3 years old, indicating that males begin to disperse around the time sexual maturation begins. Relatedness decreased with distance among pairs of females, and the mean relatedness was significantly higher between pairs of females than between pairs of males or between female–male pairs within 3 km. Closely related female–male pairs rarely (5–6%) resided in close proximity (< 3 km), compared with pairs of closely related females. Our study revealed that the potential for close inbreeding was low in Hokkaido brown bears because males are effective dispersers.

Vocalizations of ice-breeding ribbon seals Histriophoca fasciata were recorded using underwater passive acoustic methods from November 2012 to March 2014 off the Nemuro Strait, Japan. Seal presence in the strait was examined in relation to the sea ice extent in the Okhotsk Sea. Ribbon seal downsweeps were only detected when sea ice was present in the strait (February and March), with more detections in March leading up to the spring breeding season. Since ribbon seals require ice for breeding, underwater communication for breeding could be needed during the sea ice presence in this strait. Northeasterly winds were another indirect driver of ribbon seal occurrence, since winds from this direction likely transport sea ice from the central Okhotsk Sea into the Nemuro Strait. Downsweep detections decreased in the middle of the day, which is consistent with observations that seals hauled out on the ice during this time, and thus were producing fewer underwater vocalizations. Our results suggest that a decrease in the sea ice extent in the Okhotsk Sea may change the distribution of ribbon seals and impact their breeding behaviour since the Nemuro Strait region of the Okhotsk Sea is likely the southern limit of their breeding range.

A number of marine mammal species travel off Rausu, Shiretoko as feeding and breeding habitats, providing resources for tourism. However, seasonal sea ice and severe weather conditions have restricted visual observations of marine mammals off Rausu except for daytime observations between spring and fall. To compensate for this lack of information, fixed passive acoustic recording devices were deployed to monitor the presence of marine mammals during November 2012–March 2014. Pacific white-sided dolphin (Lagenorhynchus obliquidens) burst pulsed calls in July, November, and December; ribbon seal (Histriophoca fasciata) downsweeps in February and March; killer whale (Orcinus orca) pulsed calls from April to August; and sperm whale (Physeter macrocephalus) clicks in July and August were detected. Cetacean species were possibly involved in foraging since their pulsed calls or clicks were often detected during foraging. In contrast, ribbon seals were possibly involved in breeding behaviours as seal vocalizations are likely related to breeding activities. This passive acoustic monitoring will provide new insights into the ecology of diverse marine mammals off Rausu.