Maternal human habituation enhances sons' risk of human-caused mortality in a large carnivore, brown bears

Estimation of breeding population size using DNA-based pedigree reconstruction in brown bears

Robust estimates of demographic parameters are critical for effective wildlife conservation and management but are difficult to obtain for elusive species. We estimated the breeding and adult population sizes, as well as the minimum population size, in a high-density brown bear population on the Shiretoko Peninsula, in Hokkaido, Japan, using DNA-based pedigree reconstruction. A total of 1288 individuals, collected in and around the Shiretoko Peninsula between 1998 and 2020, were genotyped at 21 microsatellite loci. Among them, 499 individuals were identified by intensive genetic sampling conducted in two consecutive years (2019 and 2020) mainly by noninvasive methods (e.g., hair and fecal DNA). Among them, both parents were assigned for 330 bears, and either maternity or paternity was assigned to 47 and 76 individuals, respectively. The subsequent pedigree reconstruction indicated a range of breeding and adult (≥4 years old) population sizes: 128-173 for female breeders and 66-91 male breeders, and 155-200 for female adults and 84-109 male adults. The minimum population size was estimated to be 449 (252 females and 197 males) in 2019. Long-term continuous genetic sampling prior to a short-term intensive survey would enable parentage to be identified in a population with a high probability, thus enabling reliable estimates of breeding population size for elusive species.

Diel and monthly activity pattern of brown bears and sika deer in the Shiretoko Peninsula, Hokkaido, Japan

Mammals exhibit several types of diel activity pattern, including nocturnal, diurnal, crepuscular, and cathemeral. These patterns vary inter- and intra-specifically and are affected by environmental factors, individual status, and interactions with other individuals or species. Determining the factors that shape diel activity patterns is challenging but essential for understanding the behavioral ecology of animal species, and for wildlife conservation and management. Using camera-trap surveys, we investigated the species distributions and activity patterns of terrestrial mammals on the Shiretoko Peninsula, Hokkaido, Japan, with particular focus on brown bears and sika deer. From June to October 2019, a total of 7,530 observations were recorded by 65 camera-traps for eight species, including two alien species. The diel activity pattern of brown bears was diurnal/crepuscular, similar to that of bears in North America, but different from European populations. Bear observations were more frequent during the autumnal hyperphagia period, and adult females and sub-adults were more diurnal than adult males. In addition, bears inside the protected area were more diurnal than those outside it. These findings suggest that appetite motivation, competitive interactions between conspecifics, and human activities potentially affect bear activity patterns. Similar to other sika deer populations and other deer species, the diel activity patterns of sika deer were crepuscular. Deer showed less variation in activity patterns among months and sex-age classes, while adult males were observed more frequently during the autumn copulation period, suggesting that reproductive motivation affects their activity patterns.

Camera traps reveal interspecific differences in the diel and seasonal patterns of cicada nymph predation

Cicadas, a group of large-bodied insects, are preyed upon at both nymphal and adult stages by diverse range of vertebrates such as birds and mammals. Although the behavior of predators toward adult cicadas is well documented, there is a lack of research on the predation on cicada nymphs. In this study, camera traps deployed in conifer plantations, in which high population densities of cicadas Lyristes bihamatus emerge, were used to evaluate the seasonal and diel patterns of predation upon cicada nymphs by three predator species, namely brown bears, red foxes, and jungle crows, from May to September in 2018 and 2019 in northern Japan. Among all three species, cicada nymph predation occurred until early August when the final instar nymphs fully emerged. Bears were observed to constantly dig for cicada nymphs until early August, whereas foxes and crows were frequently observed foraging from late July to early August, during the season of L. bihamatus emergence. In contract to the powerful digging ability of bears, which facilitates efficient predation upon subterranean cicada nymphs, it is generally difficult for foxes and crows with limited or no digging ability to gain access these nymphs until the period of emergence. Cicada nymph predation by bears and crows was observed primarily during the daytime, despite the typical crepuscular/nocturnal emergence schedules of these insects. Contrastingly, the predatory activities of foxes tended to be nocturnal during the period prior to the beginning of cicada emergence, although subsequently became diurnal during the cicada emergence period. These observations indicate that the temporal activity patterns of cicada nymph predators are determined by interspecific differences in predation abilities and cicada emergence schedules. Accordingly, the findings of this study provide evidence to indicate that the timing and duration of trophic interactions between above- and belowground communities might vary among predator species, depending on their predation abilities.

Dining from the coast to the summit: Salmon and pine nuts determine the summer body condition of female brown bears on the Shiretoko Peninsula

Body condition in mammals fluctuates depending on energy intake and expenditure. For brown bears (Ursus arctos), high-protein foods facilitate efficient mass gain, while lipids and carbohydrates play important roles in adjusting dietary protein content to optimal levels to maximize energy intake. On the Shiretoko Peninsula, Hokkaido, Japan, brown bears have seasonal access to high-lipid pine nuts and high-protein salmon. To assess seasonal and annual fluctuation in the body condition of adult female brown bears in relation to diet and reproductive status, we conducted a longitudinal study in a special wildlife protection area on the Shiretoko Peninsula during 2012-2018. First, analyses of 2,079 bear scats revealed that pine nuts accounted for 39.8% of energy intake in August and salmon accounted for 46.1% in September and that their consumption by bears varied annually. Second, we calculated the ratio of torso height to torso length as an index of body condition from 1,226 photographs of 12 adult females. Results indicated that body condition continued to decline until late August and started to increase in September when salmon consumption increased. In addition, body condition began to recover earlier in years when consumption of both pine nuts and salmon was high. Furthermore, females with offspring had poorer body condition than solitary females, in particular in late August in years with low salmon consumption. Our findings suggest that coastal and subalpine foods, which are unique to the Shiretoko Peninsula, determine the summer body condition of female brown bears, as well as their survival and reproductive success.

Reforestation provides a foraging habitat for brown bears (Ursus arctos) by increasing cicada Lyristes bihamatus density in the Shiretoko World Heritage site

Reforestation, which converts abandoned farmland back into forestland by planting woody species, can provide habitat for wildlife, including the brown bear (Ursus arctos Linnaeus, 1758). In the Shiretoko World Heritage site, northern Japan, where brown bears occur at high density, conifers have been planted since the 1970s to reforest abandoned farmland. In this area, brown bears were first observed digging for cicada Lyristes bihamatus Motschulsky, 1861 = Auritibicen bihamatus (Motschulsky, 1861) nymphs from 2000. Our preliminary observations suggested that the emergence of digging behavior might be associated with reforestation. We examined whether reforestation provided a foraging habitat for brown bears. We found that digging occurred only within the restored conifer forests, but not within the natural forest. The densities of cicada nymphs in the restored forests were higher than in the natural forest. These results indicate that the reforestation of abandoned farmland provides a foraging habitat for brown bears by increasing the availability of cicada nymphs in the Shiretoko World Heritage site.