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Human habituation of large carnivores is becoming a serious problem that generates human–wildlife conflict, which often results in the removal of animals as nuisances. Although never tested, human habituation potentially reduces the fitness of adult females by reducing their offspring’s survival as well as their own, due to an increased likelihood of human-caused mortality. Here, we tested this hypothesis in brown bears inhabiting Shiretoko National Park, Japan. We estimated the frequency of human-caused mortality of independent young (aged 1–4 years) born to mothers living in areas with different maternal levels of human habituation and different proximities to areas of human activity. The overall mortality rate was higher in males than in females, and in females living near a town than those in a remote area of park. Surprisingly, more than 70% of males born to highly habituated mothers living around a remote wildlife protection area were killed by humans; this proportion is greater than that for males born to less-habituated mothers living in almost the same area. The current study clarified that interactions among maternal human habituation, birthplace (proximity to town), age, and sex determine the likelihood of human-caused mortality of brown bears at an early stage of life.

Understanding individual variations in animal behavior is crucial for ecology, evolution, conservation, and wildlife management. However, traditional bio‐logging methods have often impeded the reconstruction of long‐term behavioral patterns in mammals because of cost, battery life, and device size constraints. This study proposes and evaluates a novel method using retrospective isotope analysis of eye lenses to reconstruct mammalian feeding history, focusing on brown bears (Ursus arctos). We devised a protocol for longitudinal segregation of fragile mammalian lenses and sequentially analyzed lens fragments for carbon and nitrogen stable isotope ratios (δ13C and δ15N, respectively) in seven bears. We verified the reproducibility of the protocol by comparing isotopic patterns within lens pairs of the same bear. The results successfully reconstructed time‐series feeding histories, capturing dietary shifts during the lactation‐weaning process, reflected by δ15N from all bears and changes in corn crop (Zea mays) consumption primarily indicated by δ13C from nuisance bears. The reconstructed δ15N lactation‐weaning signal suggested that higher‐resolution isotopic information is preserved for 1–2 years after birth, with resolution declining as eye lens growth slows. The similarity of patterns between the same lens pairs supports the reliability of the method. This novel approach for reconstructing the time‐series feeding history of various mammals is simple and effective.

Body condition is an important determinant of health, and its evaluation has practical applications for the conservation and management of mammals. We developed a noninvasive method that uses photographs to assess the body condition of free-ranging brown bears ( Ursus arctos ) in the Shiretoko Peninsula, Hokkaido, Japan. First, we weighed and measured 476 bears captured during 1998–2017 and calculated their body condition index (BCI) based on residuals from the regression of body mass against body length. BCI showed seasonal changes and was lower in spring and summer than in autumn. The torso height:body length ratio was strongly correlated with BCI, which suggests that it can be used as an indicator of body condition. Second, we examined the precision of photograph-based measurements using an identifiable bear in the Rusha area, a special wildlife protection area on the peninsula. A total of 220 lateral photographs of this bear were taken September 24–26, 2017, and classified according to bear posture. The torso height:body/torso length ratio was calculated with four measurement methods and compared among bear postures in the photographs. The results showed torso height:horizontal torso length (TH:HTL) to be the indicator that could be applied to photographs of the most diverse postures, and its coefficient of variation for measurements was <5%. In addition, when analyzing photographs of this bear taken from June to October during 2016–2018, TH:HTL was significantly higher in autumn than in spring/summer, which indicates that this ratio reflects seasonal changes in body condition in wild bears. Third, we calculated BCI from actual measurements of seven females captured in the Rusha area and TH:HTL from photographs of the same individuals. We found a significant positive relationship between TH:HTL and BCI, which suggests that the body condition of brown bears can be estimated with high accuracy based on photographs. Our simple and accurate method is useful for monitoring bear body condition repeatedly over the years and contributes to further investigation of the relationships among body condition, food habits, and reproductive success.

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.

Interactions between brown bears (Ursus arctos) and anadromous salmon (Oncorhynchus spp.) constitute a unique energy pathway that facilitates nutrient cycling between marine and terrestrial ecosystems. Previous studies have documented variation in salmon consumption by brown bears; however, few have addressed potential anthropogenic factors influencing consumption. We assessed diet of brown bears on Hokkaido Island, Japan, using carbon and nitrogen stable isotopes to determine the effect of demographic (age and sex) and environmental (developed and undeveloped area) factors on salmon consumption. We collected thigh bones from 190 harvested bears from 1996 to 2011 and samples of their major dietary foods from 2009 to 2011, and we then estimated the potential contributions of these foods to the diets of brown bears using a Bayesian mixing model. Brown bears consumed more herbs, fruits, and corn than terrestrial animals or salmon at the population level. However, the dietary contribution of salmon varied widely among bears; in some cases, it comprised >30% of the total diet. Salmon consumption also varied by bear age class, sex, and location. Low salmon consumption by adult females with cubs suggested avoidance of salmon-spawning areas to minimize risk to their cubs. Bears inhabiting undeveloped areas were more likely to consume salmon than those inhabiting developed areas, suggesting that human activities restrict brown bears' salmon consumption. The lower salmon intake of Hokkaido brown bears compared with Alaskan brown bears may be attributed in part to extensive human development on Hokkaido Island, including in-stream structures that preclude salmon migrations and agricultural crops that provide an alternative food subsidy.

Understanding natal dispersal patterns is fundamental in the ecology and conservation biology of large wild carnivores. In this study, we used two approaches to determine genetic variation and dispersal patterns of brown bears in the Shiretoko Peninsula, eastern Hokkaido, Japan. The first approach was a large-scale genetic analysis. We analyzed haplotypes from the mitochondrial DNA (mtDNA) control region of 760 individual samples collected throughout the peninsula during 1998–2016. We detected seven haplotypes, including two that were confirmed for the first time. In females, the distribution of haplotypes was geographically structured, whereas haplotypes in males were distributed widely throughout the peninsula. Only some males in the lower peninsula had haplotypes that were not detected within the peninsula. The second approach was a local-scale genetic analysis, including intensive focal sampling in the Rusha area, a special wildlife protection area on the peninsula. Proportions of mtDNA haplotypes in adult bears were investigated and compared between the sexes. Although more than half of the females had the same haplotype, males had more diverse haplotypes, suggesting that they came to the Rusha area from other regions. Thus, our study revealed that mtDNA haplotype distribution has been maintained by female philopatry, and that bears exhibit male-biased dispersal. Furthermore, the lower peninsula appears to act as a contact zone between the peninsula and mainland Hokkaido, which is important for maintaining genetic diversity.

Background Sex-biased dispersal is widespread among mammals, including the brown bear ( Ursus arctos ). Previous phylogeographic studies of the brown bear based on maternally inherited mitochondrial DNA have shown intraspecific genetic structuring around the northern hemisphere. The brown bears on Hokkaido Island, northern Japan, comprise three distinct maternal lineages that presumably immigrated to the island from the continent in three different periods. Here, we investigate the paternal genetic structure across northeastern Asia and assess the connectivity among and within intraspecific populations in terms of male-mediated gene flow. Results We analyzed paternally inherited Y-chromosomal DNA sequence data and Y-linked microsatellite data of 124 brown bears from Hokkaido, the southern Kuril Islands (Kunashiri and Etorofu), Sakhalin, and continental Eurasia (Kamchatka Peninsula, Ural Mountains, European Russia, and Tibet). The Hokkaido brown bear population is paternally differentiated from, and lacked recent genetic connectivity with, the continental Eurasian and North American populations. We detected weak spatial genetic structuring of the paternal lineages on Hokkaido, which may have arisen through male-mediated gene flow among natal populations. In addition, our results suggest that the different dispersal patterns between male and female brown bears, combined with the founder effect and subsequent genetic drift, contributed to the makeup of the Etorofu Island population, in which the maternal and paternal lineages show different origins. Conclusions Brown bears on Hokkaido and the adjacent southern Kuril Islands experienced different maternal and paternal evolutionary histories. Our results indicate that sex-biased dispersal has played a significant role in the evolutionary history of the brown bear in continental populations and in peripheral insular populations, such as on Hokkaido, the southern Kuril Islands, and Sakhalin.

We examined 24 microsatellite markers to select those most suitable for individual identification and parentage tests of brown bears (Ursus arctos) based on statistical parameters and experimental error using liver samples (38 issues) from nuisance bears killed in the Akan-Shiranuka Region, eastern Hokkaido, Japan from 1996 to 2006. We found seven microsatellite markers suitable for identifying individuals (G1A, G10B, G10L, UarMU5, UarMU23, UarMU50, and UarMU51; probability of identity P id = 3.17 x 10⁻⁷; probability of identity of sibs P id₋sib = 2.23 x 10⁻³), 12 microsatellite markers suitable for parentage testing when one parent is known [G1A, G1D, G10B, G10L, G10P, UarMU5, UarMU23, UarMU50, UarMU51, UarMU59, UarMU61, and UarMU64; probability of excluding one parent (PE I = 0.9991)], and 15 microsatellite markers for parentage testing when neither parents are known [three markers added to the above: G10M, G10X, and UarMU9; probability of excluding both parents (PE II = 0.9869)].

We investigated reproductive characteristics of brown bears (Ursus arctos yesoensis) in the Oshima Peninsula, Hokkaido, Japan, based on the study of individuals harvested from 1983 to 1987. Analyses were based on age-class and reproductive status data determined for 196 females killed during the study period. The minimum age at 1st parturition was 4 years, but frequency of reproductive success among females <6 years old was notably lower than that among females greater than or equal to 6 years of age. Females <6 years old were more apt to produce single offspring and lose them during the 1st year. There appeared to be few changes in frequency of reproducing cubs among females 6-20 years of age. Females typically separated from young when young were 15-27 months old. For mature adult females, mean litter size was 1.8, and interval between births was 2.3-3.0 years. Embryo loss and neonatal mortality were uncommon.

To further elucidate the migration history of the brown bears (Ursus arctos) on Hokkaido Island, Japan, we analyzed the complete mitochondrial DNA (mtDNA) sequences of 35 brown bears from Hokkaido, the southern Kuril Islands (Etorofu and Kunashiri), Sakhalin Island, and the Eurasian Continent (continental Russia, Bulgaria, and Tibet), and those of four polar bears. Based on these sequences, we reconstructed the maternal phylogeny of the brown bear and estimated divergence times to investigate the timing of brown bear migrations, especially in northeastern Eurasia. Our gene tree showed the mtDNA haplotypes of all 73 brown and polar bears to be divided into eight divergent lineages. The brown bear on Hokkaido was divided into three lineages (central, eastern, and southern). The Sakhalin brown bear grouped with eastern European and western Alaskan brown bears. Etorofu and Kunashiri brown bears were closely related to eastern Hokkaido brown bears and could have diverged from the eastern Hokkaido lineage after formation of the channel between Hokkaido and the southern Kuril Islands. Tibetan brown bears diverged early in the eastern lineage. Southern Hokkaido brown bears were closely related to North American brown bears.