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Eight reproductively isolated populations have been described from the extensive spotted seal's range. Of these, the population from the Peter the Great Bay (Sea of Japan) is the only one that lost its ecological relationship to ice. Seals of this population breed on island shores. Based on the analysis of published data, this review summarizes information about the main features of the biology and ecology of the spotted seal population in the Peter the Great Bay that distinguish it from other populations. Over the last 25 years, the size of this population has increased three to four-fold. This happened despite the poor condition of the species in some parts of the range. The most serious threats to this population are accidental entanglement and death of seals in fishing gear and habitat pollution by toxic substances. The prospects for survival of the population in current conditions are evaluated. The spotted seal population in the Peter the Great Bay is extremely important for the conservation of the genetic diversity, which increases the chances to survive for the species in general. The breeding grounds of spotted seals in the Peter the Great Bay are protected by the Far Eastern Marine Biosphere Reserve.
Published online 25 September, 2024; Print publication 31 October, 2024
The distribution of the Japanese serow (Capricornis crispus) has recently expanded to low-elevation areas. However, there is little ecological information available for this species in such areas. This study aimed to elucidate the feeding habits of the Japanese serow in the Ome Hills, central Japan, a low-elevation area characterized by the dominance of evergreen broad-leaved trees in the shrub layer. Through the analysis of 115 fecal samples collected between 2019 and 2020, our findings revealed that Japanese serow consistently foraged on monocot leaves and dicot leaves and stems throughout the year. Furthermore, a detailed examination of feeding signs indicated a preference for graminoids in both coniferous plantations and deciduous broad-leaved forests across all seasons.
Published online 3 July, 2024; Print publication 31 October, 2024
Ungulates exhibit various and persistent behavioral responses to anthropogenic disturbance. However, information about natural behavior of sika deer with regard to their flight response is lacking. To clarify the effects of internal and external factors on the flight response of sika deer, it is crucial to initially evaluate this response in areas with low anthropogenic disturbance. Therefore, this study aimed to investigate the flight distance (FD) of sika deer in response to human presence on a forest road and clarify the influences of both internal and external factors on FD. Although there was no significant difference in the number of deer observed per 1 km between the fawn-rearing and rutting seasons, the numbers of males and females significantly varied seasonally, with more females observed in the fawn-rearing and more males in rutting season. FD was significantly influenced by herd composition, herd size, deer positioning, and terrain ruggedness index, indicating that females with fawn, larger herds, and deer in uphill or areas with high terrain ruggedness index tended to flee farther distances. Consequently, given the influences of internal and external factors on FD, as demonstrated in the present study, continuous monitoring of FD could provide valuable insights into wildlife management.
Published online 3 July, 2024; Print publication 31 October, 2024
The sika deer (Cervus nippon) is known to exhibit north-south variations in body size, but growth patterns and sexual size differences are not well studied. This study compared age-related changes in the hindfoot length and body weight of deer in the northern and southern populations in Japan. Hindfoot lengths of the northern deer were 12% (males) and 9% (females) longer and the body weights were 19% (males) and 8% (females) heavier than the southern deer. Hindfoot length increased from fawns to two years of age and then remained stable in both sexes in the northern deer, while it increased to yearlings in both sexes in the southern deer. Male body weight significantly increased until three years in the northern deer and until two years in the southern deer. Female body weight significantly increased until two years both in the northern and southern deer. Male/female ratios were greater in the northern deer than in the southern deer. We showed that 1) the northern deer were larger, 2) males were larger than females in both places, 3) males grew faster for a longer period than females, and 4) sexual dimorphism was more pronounced in the northern population.
Published online 5 August, 2024; Print publication 31 October, 2024
Postnatal growth and vocalization development in the Ussurian tube-nosed bat Murina ussuriensis were investigated under captive conditions. Response calls between mothers and their young were also analyzed. Parturition occurred in early June. At birth, forearm length averaged 12.7 mm, and body weight averaged 1.43 g. The newborn young opened their eyes around five days after birth. From days five to 20, their forearm length and body weight grew noticeably. The calls of newborns had a peak frequency (PF) of 42 kHz and lasted 14 ms, while nursing females had a lower PF of 27 kHz. The females also used these calls to respond to their young. As the young grew, the PF of their short calls increased rapidly from 12 to 23 days of age and reached 68 kHz at 31 days of age. The duration of these calls decreased rapidly from three to 23 days of age and then gradually decreased to 2.5 ms, similar to adult echolocation calls. When the mother bat made echolocation calls, the young quickly responded by emitting isolation calls. As the young grew, the PF of their calls changed to around 35 kHz, which was lower than that in short calls.
Published online 5 August, 2024; Print publication 31 October, 2024
Grizzled giant squirrel Ratufa macroura dandolena is confined to a few forest fragments in India, lacks population status, and is often ignored in management. The northernmost distribution is the Cauvery Wildlife Sanctuary where the habitat is threatened due to anthropogenic activities. Therefore, occupancy and habitat requirements for their activities are essential to manage them. We sampled 158 grid cells for the occupancy of squirrels and followed two adult males and two adult females for ten days to study their behavior. The detection probability, naïve occupancy, and the estimate of occupancy were 0.10, 0.13, and 0.42, respectively. The basal area and canopy cover positively influenced the occupancy, while the tree height and forest cover negatively influenced it. Males rest more while females spend more on feeding and moving. The day path length and home range sizes of females were more than those of males. Of the 25 plant species fed by squirrels, Albizia amara, Muntingia calabura, Tamarindus indica, and Ziziphus oenoplia are the most fed plants. Of the 255 nests recorded, 42.35% were on T. indica and 23.14% were on Terminalia arjuna. More than 80% of the nests were between 11 and 20 m in the tree.
Published online 5 August, 2024; Print publication 31 October, 2024
We evaluated the fine-scale spatiotemporal habitat use by the Japanese hare (Lepus brachyurus) in daily active (nighttime) and inactive (daytime) periods during heavy snowfall seasons in northeastern Japan. To reveal the habitat use by hares considering the relationship with predators, we conducted camera trap surveys between January and March in 2021 and 2022 in 150 ha and footprint tracking surveys between January and March in 2022 and 2023 in 400 ha. Consequently, the shooting events of hare camera traps were significantly positively related to canopy openness, slope, and those of martens, but not related to those of foxes. The diel activity of hares overlapped with those of martens and foxes, but did not overlap with that of foxes in daytime. There were no significant differences in time lags between appearance times of hares and martens, or hares and foxes. In contrast, the forms (i.e., resting sites) of hares during the inactive period (daytime) were located in areas with closed canopies and low horizontal openness. These findings suggest that habitat selection by hares may be based on foraging rather than terrestrial predator avoidance during the active period (nighttime), and on both aerial and terrestrial predator avoidance during the inactive period (daytime).
Published online 10 September, 2024; Print publication 31 October, 2024
Mountains are home to many endemic species. Such organisms are isolated by the environmental gradient around mountains. Such isolation would affect various kinds of populations' diversity of mammalian species among mountains in Japan. This study examined the skull morphology of the lesser Japanese shrew mole Dymecodon pilirostrisTrue, 1886 (Eulipotyphla: Talpidae), which is distributed in high mountain areas of Honshu, Shikoku, and Kyushu Islands, Japan. Univariate and multivariate analyses were performed on the basis of 19 measurements obtained from 104 skull specimens. The results showed morphological differences among mountain ranges, in overall skull size, teeth row length, and mandibular height. This morphological divergence was revealed in mountain ranges in Honshu, even among the neighboring mountain ranges from Akaishi, Kiso, and Hida, so-called the Japan Alps. The geographic divergent pattern suggests that the morphological evolution of D. pilirostris occurred in each mountain island in Japan.
Published online 5 August, 2024; Print publication 31 October, 2024
Investigating activity patterns of wild mammals is important for proper conservation and management. Brown bears generally have a crepuscular activity pattern; however, their seasonal variation and differences among sex-age classes have not been quantitatively investigated in Japan. Using 97 camera traps located in the Akan–Shiranuka in Hokkaido, Japan, we monitored the diurnal activity patterns of brown bears from April to November between 2016 and 2018. We divided 2183 capture events into four sex-age classes; adult males (AMs), solitary adult females (SFs), females with cubs of the year (FCs), and subadults (SAs) for four seasons; spring (April–May), early summer (June–July), late summer (August–September), and autumn (October–November). The activity patterns of AMs, SFs, and FCs were crepuscular or vesperal, whereas those of SAs were diurnal from spring to late summer. In autumn, all sex-age classes changed their activity patterns to more nocturnal or vesperal. SFs and AMs had similar activities, especially in the mating season (spring and early summer) with high overlap coefficients. The FCs were more active during daytime compared to AMs, which might be a strategy to avoid temporally infanticidal males. These results suggest that human activity and intraspecific relationships influence brown bear activity patterns.
Tunnel construction by captive long-clawed shrews (Sorex unguiculatus) was investigated in an experimental cage designed for the observation of subterranean activity. Five subadult individuals were observed constructing tunnel systems in the experimental cage, but one newborn individual could not make a complex system. The tunnel system consisted of two parts: the main burrows at a depth of approximately 20–30 cm from the ground surface and surface runways at a depth of 3–7 cm. In a tunnel system, there were 2–4 permanent vertical passages with entrances to the ground surface and 3–5 blind chambers and burrows. To complete the tunnel system construction, a shrew usually spent 5–6 days. Two types of digging were recognized: (1) digging surface runways and short vertical passages and (2) digging deep tunnels.
Published online 5 August, 2024; Print publication 31 October, 2024
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