著者

内藤 靖彦 Boeuf Burney J. Le 浅賀 朋宏 Huntley Anthony C. Yasuhiro Naito Burney J. Le Boeuf Tomohiro Asaga Anthony C. Huntley

雑誌

南極資料 = Antarctic Record (ISSN:00857289)

巻号頁・発行日

vol.33, no.1, pp.1-9, 1989-03

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南極アザラシの冬季潜水行動を知るために開発した長期潜水記録計の現場実験を, 回収が容易なキタゾウアザラシ(Mirounga angustirostris)を用いて行った。現場実験はキタゾウアザラシの連続的な深い潜水行動を知ることを主要な目的としてカリフォルニア, アニュ・ノエボ海岸で行った。1987年2月繁殖終了後の雌の成獣に記録計を装着し, 換毛のため再上陸した5月に記録計の回収を行い, 潜水行動記録として初めて73日間におよぶ長期連続記録を得た。潜水回数は, 73日間5024回であり, 1時間平均2.9回の潜水を行った。全潜水の平均深度は463.9±147mであり, 平均潜水時間は17.1±3.4分であつた。最大潜水深度と最大潜水時間は, 934mと33.5分であつた。最大潜水深度は実測された鰭脚類の深度としては最も深い記録であった。潜水は初めの4日間は深度を徐々に増し, 500m深度に達すると安定した。しかし, 潜水深度は昼夜で変わり, また約20日単位でも変化した。潜水時間は長期にも安定していた。ESI (Extended Surface Interval)直後の潜水は非常に浅い潜水から再開され, 数回の深度を増す潜水を経て通常の深度に達した。以上の実験の結果, 本記録計は装着による動物行動への影響がないことが判明し, 南極アザラシでも有効に利用できることがわかった。Seventy-three days long diving record of an adult female northern elephant seal (Mirounga angustirostris) was obtained using the long-term time depth recorder which was developed for Antarctic seal research by the National Institute of Polar Research, Tokyo. It was observed that the female northern elephant seal dived to a great depth continuously for a long period. It dived 5024 times during 73 days, 2.9 times per hour on the average. The mean dive depth and duration were 463.9±147m and 17.1±3.4min, the maximum values being 934m and 33.5min. The dive depth increased gradually on the first 4 days. After that, it fluctuated diurnally, while the dive duration remained rather stable. Following the extended surface intervals (ESIs : defined as surface intervals longer than 10min) dives were shallow but the depth increased gradually.

著者

Burney J. Le Boeuf

雑誌

Memoirs of National Institute of Polar Research. Special issue

巻号頁・発行日

vol.58, pp.89-100, 2004-03

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The aim of these studies was to determine local movements of hunting white sharks (Carcharodon carcharias) near a seal rookery and global movements during migration. Seven adults were monitored locally with attached ultrasonic tags that received and telemetered animal position and behavior via an array of three-acoustic-positioning (RAP) buoys moored off Ano Nuevo Island, California. Migratory movements of 6 adults departing this island and nearby Southeast Farallon Island were tracked for 2-6 months with attached pop-up satellite archival tags. Sharks began hunting seals at Ano Nuevo Island in October, spending 40% of the day patrolling the 1 km2 receptive field within 400 m of the island at a depth of 30 m or less. For six weeks, they did not stray far or long from the area, were equally active at night as by day, were non-territorial, and fed infrequently. This nearshore phase at both island rookeries ended abruptly in winter as the sharks moved offshore to a region of the subtropical eastern Pacific half way to Hawaii. An adult male went further, traveling to Hawaii where it remained until migrating back to California, only to repeat the journey the following year. Electronic tagging provides vital information on the hunting and migratory behavior of this apex predator.