担当区分：筆頭著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：Public Library of Science (PLoS)  

The rapidly growing number of wind farms is an increasing threat to many bat species and populations worldwide. Monitoring and prediction of bat collision risk requires techniques capable of quantifying bat movements over large spatial areas. Marine radar systems are highly effective tools for observing flying animals over large surveillance areas. However, the detection capability of marine radar systems has rarely been validated for bats. In this study, we sought to validate the effectiveness of a commercially available X-band marine radar in detecting Asian particolored bats ( Vespertilio sinensis ). To achieve this goal, we first examined the effect of adjusting the height of the radar antenna to reduce ground clutter. By lowering the antenna height from 2.2 m to 0.4 m, the visible area on radar images was increased by a factor of 2.1 over the entire 1.5 km observation range. Subsequently, we conducted radar observations under conditions where radar-detected targets could be reliably identified as bats. To acquire ground truth bat flight trajectories, we tracked bats at dusk using an ornithodolite simultaneously with radar scans. We manually tracked bat echoes on radar images and matched them to ornithodolite trajectories. Following this procedure, we identified 25 radar tracks as bat flights. These tracks were analyzed to determine the probability of echo detection (detection versus non-detection) as a function of distance from the radar by applying a generalized linear mixed model. The model analysis demonstrated that X-band marine radar was capable of detecting bat flights at a distance of up to 1.0 km, with a probability of detection exceeding 70%. Our results suggest that X-band marine radar can be an appropriate tool for monitoring bat movements, and also contribute to the establishment of range settings that should be considered for radar bat surveys.

DOI： 10.1371/journal.pone.0337422

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担当区分：筆頭著者,　責任著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：Frontiers Media SA  

In a wide range of heterothermic mammals, hibernation interrupts the reproductive cycle by forcing reproductive delays. In hibernating bats with delayed fertilization, an opportunity for sperm competition is enhanced by extending a time-window between copulations and fertilization. In order to achieve greater fertilization success, males are expected to show adaptations for sperm competition by increasing their opportunities for mating over an extended period. We aimed to clarify the physiological and behavioral characteristics of male bats experiencing increased risks of sperm competition. We investigated the characteristics of the reproductive cycle of the little horseshoe bat (Rhinolophus cornutus), and examined whether males retain reproductive physiology related to sexual behavior, and attempt to copulate with females even during the hibernation period. Field observations and histological examinations of the reproductive cycle confirmed that females, having mated in the autumn, store spermatozoa in the uterus during hibernation and give birth in the early summer to just one offspring per year, thus males face a low certainty of successful fertilization. Although their testes regressed rapidly and their testosterone levels were lower during winter than in autumn, males stored motile spermatozoa in their cauda epididymides from autumn throughout the winter. During hibernation, we found that males occasionally aroused from torpor and attempted to mate forcibly with torpid females. Forced copulations appear to increase a male’s chances of obtaining a mate while avoiding pre-copulatory female choice. Epididymal sperm storage could be advantageous for males in allowing them to extend their potential mating period even though their testes have regressed. We also found that some hibernating nulliparous females were ready for fertilization in spring after hibernation, whereas few parous females appeared in the same roost. In contrast to males, forced copulations would be maladaptive for females because they cannot opt for higher-quality males while in torpor. Females that have experienced sexual coercion when young may subsequently avoid hibernacula where adult males are present.

DOI： 10.3389/fphys.2023.1241470

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Science and Business Media LLC  

Abstract

The collection of wildlife tracking information throughout a species’ entire life cycle is important for comprehensive ecological elucidation and the establishment of practical protected areas. Although streaked shearwater (SS) is a seabird species for which biologging techniques are highly developed, there have been no reports of successful global positioning system (GPS) tracking during the early breeding and non-breeding seasons, when recapture is difficult. In this study, we succeeded in long-term GPS tracking, obtaining highly accurate tracking data during the non-breeding season from November to March and the early breeding season from April to July. We discuss the relationship between prey distribution and the marine environment to understand the species’ foraging habitat preferences. In September 2018, we attached GPS tags to birds breeding on Toshima, in the Izu Islands, and recaptured two birds in August 2020 and 2022. The tags worked for 277 and 549 days and fixed 23,510 and 37,233 positions, respectively. During the early breeding season, the foraging area had low sea surface temperatures (SST) and high chlorophyll-a (Chl-a) concentrations and moved northward as the season progressed. During the non-breeding season, one bird wintered in the South China Sea and the other off northern New Guinea. In the South China Sea, SS preferred sea areas with an average SST of 26 °C and high Chl-a concentrations (> 0.8mg/m³), whereas off northern New Guinea, SS preferred an area with an average SST of 29 °C. The foraging area used during the early breeding season depended on the optimal water temperature zone for their primary prey—Japanese Anchovy. The foraging areas used during the non-breeding season matched the optimal water temperature zones of the main fish distributed in each sea area. The GPS tracking data obtained in this study, while not a statistically sufficient sample size, are valuable and provide new insights into the environmental preferences of SS during early breeding and non-breeding seasons; life stages for which little information is available.

DOI： 10.1186/s40317-024-00397-8

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その他リンク： https://link.springer.com/article/10.1186/s40317-024-00397-8/fulltext.html

掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Science and Business Media LLC  

Abstract

Radar is a powerful technology for surveys of avian movements. Validating the accuracy of radar detection is essential when establishing quantitative criteria for tracking bird trajectories and counting bird flocks. This study clarifies the positional and biological factors influencing the probability of detection (POD) and echo size on X-band marine radar. The bird trajectory for validation was obtained by ornithodolite at the same time as the radar scan. Distance was found to have a negative effect on POD and echo size, while elevation angle positively affected POD. Body mass and flock size positively affected POD and echo size. In predicting detection performance, the survey distance required to achieve 50% POD was 750 m or less for Grey-faced Buzzard, the lightest target species, but up to 1800 m for a pair of Bewick’s Swan. Our study provides survey and analysis procedures that allow for efficient validation using ornithodolites. Then, we identify the range settings that should be considered for target species and contribute to establishing criteria for quantitative radar bird surveys.

DOI： 10.1038/s41598-024-73198-x

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その他リンク： https://www.nature.com/articles/s41598-024-73198-x

掲載種別：研究論文（学術雑誌）  

DOI： 10.2208/jscejj.24-26006

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総ページ数：xi,360p   記述言語：日本語

CiNii Books

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総ページ数：vii, 177p, 図版 [2] 枚   記述言語：日本語

CiNii Books

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開催年月日： 2025年10月

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開催年月日： 2025年9月

会議種別：口頭発表（一般）  

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開催年月日： 2024年9月

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開催年月日： 2024年9月

記述言語：日本語   会議種別：ポスター発表  

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開催年月日： 2024年5月

会議種別：ポスター発表  

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