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岩田 高志大学院海事科学研究科 海事科学専攻助教
研究活動情報
■ 論文- Abstract Female Weddell seals (Leptonychotes weddellii) display a mixed capital-income breeding strategy, losing up to 40% of their body mass between birthing and weaning their pups. How and when they regain energy stores, however, remains to be fully explored. To better understand the foraging by lactating Weddell seals, we fitted time-depth recorders and head-mounted cameras on 26 seals in Erebus Bay, Ross Sea, for ~ 5 days in November and December 2018 and 2019. We aimed to (1) identify prey species and foraging depth and (2) investigate relationships between seal physiology and demographics and probability of foraging. We recorded 2782 dives, 903 of which were > 50 m, maximum depth was 449.3 m and maximum duration was 31.1 min. Pup age likely contributes to the probability of a lactating Weddell seal foraging (Est. = 1.21 (SD = 0.61), z = 1.97, p = 0.0484). Among 846 prey encounters, the most frequent prey items were crustaceans (46.2%) and Antarctic silverfish (Pleuragramma antarcticum, 19.0%); two encounters were observed with juvenile Antarctic toothfish (Dissostichus mawsoni, 0.2%). We identified substantial variability in foraging behaviour, individually and between locations, and found that lactating seals target many species and some may specialise on certain prey groups.Springer Science and Business Media LLC, 2024年08月, Polar Biology[査読有り]研究論文（学術雑誌）
- Abstract Finless porpoises (Neophocaena asiaeorientalis) currently face population decline caused by significant human activities and are categorized as endangered on the International Union for Conservation of Nature (IUCN) Red List; however, information on their habitats is currently insufficient. Although conducting visual surveys to determine the distribution of cetaceans is common, visual observation of finless porpoises is challenging owing to their specific morphological and ecological characteristics. In this study, we developed an environmental DNA (eDNA) assay for species-specific detection of finless porpoises. To test the utility of the assay, we conducted a visual survey in parallel with an eDNA survey by collecting water samples from 50 sites throughout Osaka Bay. We visually found a finless porpoise at one location and detected eDNA at nine sites, including sites near the visual observation site and those with rare sightings of finless porpoises. Therefore, in this study, we suggest that the use of eDNA analysis for distribution surveys of finless porpoises will enable more efficient surveys. The proposed eDNA technique can not only be applied to the distribution surveys finless porpoises but also to those of other cetacean species.Springer Science and Business Media LLC, 2024年05月, Conservation Genetics Resources[査読有り]研究論文（学術雑誌）
- Abstract Top marine predators, such as odontocetes, pinnipeds, and seabirds, are known to forage around fishing boats as fishermen aggregate and/or discard their prey. Recently, incidents of humpback whales interacting with fishing boats have been reported. However, whether humpback whales utilise discard fish as a food source and how they forage around fishing boats is unknown. This study reports, for the first time, the foraging behaviour of a humpback whale around fishing boats. Three whales were tagged using a suction‐cup tag containing a video camera, and a behavioural data logger in the coastal area of Tromsø, Norway. Video data from one tagged whale showed that the whale remained in close vicinity of fishing boats for 43 min, and revealed the presence of large numbers of dead fish, fish‐eating killer whales, fishing boats, and fishing gear. In waters with large numbers of dead fish, the whale raised its upper jaw, a motion associated with engulfing discard fish from fishing boats, and this feeding behaviour differed markedly from lunge‐feeding observed in two other whales in the same area. This behaviour was defined as “pick‐up feeding”. No lunge feeding was seen on the data logger when the whale foraged around fishing boats. This study highlights a novel humpback whale foraging strategy: low energy gain from scattered prey but also low energy costs as high‐energy lunge feeding is not required.Wiley, 2023年11月, Ethology[査読有り]研究論文（学術雑誌）
- Abstract Attaching cameras to marine mammals allows for first-hand observation of underwater behaviours that may otherwise go unseen. While studying the foraging behaviour of 26 lactating Weddell seals (Leptonychotes weddellii) in Erebus Bay during the austral spring of 2018 and 2019, we witnessed three adults and one pup investigating the cavities of Rossellidae glass sponges, with one seal visibly chewing when she removed her head from the sponge. To our knowledge, this is the first report of such behaviour. While the prey item was not identifiable, some Trematomus fish (a known Weddell seal prey) use glass sponges for shelter and in which to lay their eggs. Three of the four sponge foraging observations occurred around 13:00 (NZDT). Two of the three sponge foraging adults had higher-than-average reproductive rates, and the greatest number of previous pups of any seal in our study population, each having ten pups in 12 years. This is far higher than the study population average of three previous pups (± 2.6 SD). This novel foraging strategy may have evolved in response to changes in prey availability, and could offer an evolutionary advantage to some individuals that exploit prey resources that others may not. Our observations offer new insight into the foraging behaviours of one of the world’s most studied marine mammals. Further research on the social aspects of Weddell seal behaviour may increase our understanding of the extent and mechanisms of behavioural transfer between conspecifics. Research into the specific foraging behaviour of especially successful or experienced breeders is also warranted.Springer Science and Business Media LLC, 2023年05月, Polar Biology, 46(7) (7), 611 - 621[査読有り]研究論文（学術雑誌）
- Elsevier BV, 2021年03月, iScience, 24(4) (4), 102221 - 102221[査読有り]研究論文（学術雑誌）
- Animal-borne video loggers are powerful tools for investigating animal behaviour because they directly record immediate and extended peripheral animal activities; however, typical video loggers capture only a limited area on one side of an animal being monitored owing to their narrow field of view. Here, we investigated the resting behaviour of humpback whales using an animal-borne omnidirectional video camera combined with a behavioural data logger. In the video logger footage, two non-tagged resting individuals, which did not spread their flippers or move their flukes, were observed above a tagged animal, representing an apparent bout of group resting. During the video logger recording, the swim speed was relatively slow (0.75 m s-1), and the tagged animal made only a few strokes of very low amplitude during drift diving. We report the drift dives as resting behaviour specific to baleen whales as same as seals, sperm whales and loggerhead turtles. Overall, our study shows that an omnidirectional video logger is a valuable tool for interpreting animal ecology with improved accuracy owing to its ability to record a wide field of view.Elsevier BV, 2021年02月, Behavioural Processes, 186, 104369 - 104369, 英語[査読有り]研究論文（学術雑誌）
- Monitoring the body condition of free-ranging marine mammals at different life-history stages is essential to understand their ecology as they must accumulate sufficient energy reserves for survival and reproduction. However, assessing body condition in free-ranging marine mammals is challenging. We cross-validated two independent approaches to estimate the body condition of humpback whales (The Royal Society, 2021年01月, Proceedings of the Royal Society B: Biological Sciences, 288(1943) (1943), 20202307 - 20202307, 英語
Megaptera novaeangliae ) at two feeding grounds in Canada and Norway: animal-borne tags (n = 59) and aerial photogrammetry (n = 55). Whales that had a large length-standardized projected area in overhead images (i.e. whales looked fatter) had lower estimated tissue body density (TBD) (greater lipid stores) from tag data. Linking both measurements in a Bayesian hierarchical model to estimate the true underlying (hidden) tissue body density (uTBD), we found uTBD was lower (−3.5 kg m −3 ) in pregnant females compared to adult males and resting females, while in lactating females it was higher (+6.0 kg m −3 ). Whales were more negatively buoyant (+5.0 kg m −3 ) in Norway than Canada during the early feeding season, possibly owing to a longer migration from breeding areas. While uTBD decreased over the feeding season across life-history traits, whale tissues remained negatively buoyant (1035.3 ± 3.8 kg m −3 ) in the late feeding season. This study adds confidence to the effectiveness of these independent methods to estimate the body condition of free-ranging whales.[査読有り]研究論文（学術雑誌） - 2020年08月, 哺乳類科学, 60(2) (2), 281 - 296, 日本語海生哺乳類学におけるバイオロギングの利用と発展[査読有り]研究論文（学術雑誌）
- Central place foraging theory (CPF) has been used to predict the optimal patch residence time for air-breathing marine predators in response to patch quality. Humpback whales (Megaptera novaeangliae) forage on densely aggregated prey, which may induce drastic change in prey density in a single feeding event. Thus, the decision whether to leave or stay after each feeding event in a single dive in response to this drastic change, should have a significant effect on prey exploitation efficiency. However, whether humpback whales show adaptive behavior in response to the diminishing prey density in a single dive has been technically difficult to test. Here, we studied the foraging behavior of humpback whales in response to change in prey density in a single dive and calculated the efficiency of each foraging dive using a model based on CPF approach. Using animal-borne accelerometers and video loggers attached to whales, foraging behavior and change in relative prey density in front of the whales were successfully quantified. Results showed diminishing rate of energy intake in consecutive feeding events, and humpback whales efficiently fed by bringing the rate of energy intake close to maximum in a single dive cycle. This video-based method also enabled us to detect the presence of other animals around the tagged whales, showing an interesting trend in behavioral changes where feeding duration was shorter when other animals were present. Our results have introduced a new potential to quantitatively investigate the effect of other animals on free-ranging top predators in the context of optimal foraging theory.2019年, PloS one, 14(2) (2), e0211138, 英語, 国際誌[査読有り]研究論文（学術雑誌）
- 2018年09月, Frontiers in Marine Science, 5, 333, 英語[査読有り]研究論文（学術雑誌）
- CELL PRESS, 2017年11月, CURRENT BIOLOGY, 27(21) (21), R1154 - R1155, 英語[査読有り]研究論文（学術雑誌）
- The foraging strategy of many animals is thought to be determined by their past experiences. However, few empirical studies have investigated whether this is true in diving animals. We recorded three-dimensional movements and mouth-opening events from three Antarctic fur seals during their foraging trips to examine how they adapt their behaviour based on past experience-continuing to search for prey in the same area or moving to search in a different place. Each dive cycle was divided into a transit phase and a feeding phase. The linear horizontal distance travelled after feeding phases in each dive was affected by the mouth-opening rate during the previous 244 s, which typically covered two to three dive cycles. The linear distance travelled tended to be shorter when the mouth-opening rate in the previous 244 s was higher, i.e. seals tended to stay in the same areas with high prey-encounter rates. These results indicate that Antarctic fur seals follow decision-making strategies based on the past foraging experience over time periods longer than the immediately preceding dive.ROYAL SOC, 2015年07月, BIOLOGY LETTERS, 11(7) (7), 20150227, 英語[査読有り]研究論文（学術雑誌）
- Albatrosses are known to expend only a small amount of energy during flight. The low energy cost of albatross flight has been attributed to energy-efficient gliding (soaring) with sporadic flapping, although little is known about how much time and energy albatrosses expend in flapping versus gliding during cruising flight. Here, we examined the heart rates (used as an instantaneous index of energy expenditure) and flapping activities of free-ranging black-browed albatrosses (Thalassarche melanophrys) to estimate the energy cost of flapping as well as time spent in flapping activities. The heart rate of albatrosses during flight (144 beats min(-1)) was similar to that while sitting on the water (150 beats min(-1)). In contrast, heart rate was much higher during takeoff and landing (ca. 200 beats min(-1)). Heart rate during cruising flight was linearly correlated with the number of wing flaps per minute, suggesting an extra energy burden of flapping. Albatrosses spend only 4.6 +/- 1.4% of their time flapping during cruising flight, which was significantly lower than during and shortly after takeoff (9.8 +/- 3.5%). Flapping activity, which amounted to just 4.6% of the time in flight, accounted for 13.3% of the total energy expenditure during cruising flight. These results support the idea that albatrosses achieve energy-efficient flight by reducing the time spent in flapping activity, which is associated with high energy expenditure.COMPANY OF BIOLOGISTS LTD, 2013年08月, JOURNAL OF EXPERIMENTAL BIOLOGY, 216(16) (16), 3175 - 3182, 英語[査読有り]研究論文（学術雑誌）
- Northern fur seals (Callorhinus ursinus) continue to dive and forage during foraging trips in cold water. Although their dense fur may prevent a decrease in body temperature, they must spend considerable time grooming to maintain a layer of trapped air in their fur. This study examined grooming and shaking behaviours, which are high-energy cost movements, using an accelera-tion data logger to accurately estimate the energy budget of these aquatic mammals. The authors examined the consistency between the behav-ioural records obtained using an animal-borne acceleration data logger and video observations of a captive northern fur seal. Grooming behav-iour was defined as rubbing the body with its flip-pers with rolling that was occasionally associated with shaking. Grooming behaviour was detected by low-frequency components of lateral and dor-soventral acceleration resulting from rolling and high-frequency components of lateral accelera-tion resulting from rubbing and shaking. These observations show that the grooming and shaking behaviours of northern fur seals can be accurately detected using an acceleration data logger. We suggest that the energy budgets of free-ranging northern fur seals can be more accurately esti-mated using an index of energy costs and benefits captured using an acceleration data logger.2013年, Aquatic Mammals, 39(4) (4), 378 - 384, 英語[査読有り]研究論文（学術雑誌）
- 2013年, Czech Polar Reports, 3, 82 - 86[査読有り]
- WILEY-BLACKWELL, 2012年04月, MARINE MAMMAL SCIENCE, 28(2) (2), 345 - 357, 英語[査読有り]研究論文（学術雑誌）
- P>1. Breath-hold divers are widely assumed to descend and ascend at the speed that minimizes energy expenditure per distance travelled (the cost of transport (COT)) to maximize foraging duration at depth. However, measuring COT with captive animals is difficult, and empirical support for this hypothesis is sparse. 2. We examined the scaling relationship of swim speed in free-ranging diving birds, mammals and turtles (37 species; mass range, 0 center dot 5-90 000 kg) with phylogenetically informed statistical methods and derived the theoretical prediction for the allometric exponent under the COT hypothesis by constructing a biomechanical model. 3. Swim speed significantly increased with mass, despite considerable variations around the scaling line. The allometric exponent (0 center dot 09) was statistically consistent with the theoretical prediction (0 center dot 05) of the COT hypothesis. 4. Our finding suggests a previously unrecognized advantage of size in divers: larger animals swim faster and thus could travel longer distance, search larger volume of water for prey and exploit a greater range of depths during a given dive duration. 5. Furthermore, as predicted from the model, endotherms (birds and mammals) swam faster than ectotherms (turtles) for their size, suggesting that metabolic power production limits swim speed. Among endotherms, birds swam faster than mammals, which cannot be explained by the model. Reynolds numbers of small birds (< 2 kg) were close to the lower limit of turbulent flow (similar to 3 x 105), and they swam fast possibly to avoid the increased drag associated with flow transition.WILEY-BLACKWELL, 2011年01月, JOURNAL OF ANIMAL ECOLOGY, 80(1) (1), 57 - 68, 英語[査読有り]研究論文（学術雑誌）
- This study aimed to evaluate the utility of acceleration data for monitoring the swimming and foraging behavior of a marine mammal. We examined the matches between the acceleration records obtained by animal-borne data loggers and the video observation of flipper movement and prey capture for a captive northern fur seal. The results showed that 93% of forelimb strokes were successfully detected. Furthermore, elevated swim speed, large changes in body angle and elevated stroke frequency were detected during prey pursuit or capture events. These results suggest that the swimming costs and the number of prey pursuits or captures can be estimated in free-ranging otariids using acceleration data.日本水産學會, 2009年11月, 日本水産學會誌 = Bulletin of the Japanese Society of Scientific Fisheries, 75(6) (6), 989 - 994, 日本語[査読有り]研究論文（学術雑誌）
- Albatrosses fly many hundreds of kilometers across the open ocean to find and feed upon their prey. Despite the growing number of studies concerning their foraging behaviour, relatively little is known about how albatrosses actually locate their prey. Here, we present our results from the first deployments of a combined animal-borne camera and depth data logger on free-ranging black-browed albatrosses (Thalassarche melanophrys). The still images recorded from these cameras showed that some albatrosses actively followed a killer whale (Orcinus orca), possibly to feed on food scraps left by this diving predator. The camera images together with the depth profiles showed that the birds dived only occasionally, but that they actively dived when other birds or the killer whale were present. This association with diving predators or other birds may partially explain how albatrosses find their prey more efficiently in the apparently 'featureless' ocean, with a minimal requirement for energetically costly diving or landing activities.PUBLIC LIBRARY SCIENCE, 2009年10月, PLOS ONE, 4(10) (10), e7322, 英語[査読有り]研究論文（学術雑誌）
- 2022年04月, 日本生態学会誌, 73(1) (1), 1 - 9
- 2017年, 勇魚, 65, 18 - 22タイ湾のカツオクジラ調査[招待有り]
- 2016年, JARE DATA REPORTS (Marine Biology), 56, 1 - 20Plankton sampling by the training vessel Umitaka-maru in the Indian sector of the Southern Ocean in the austral summer of 2012/2013.速報，短報，研究ノート等（大学，研究機関紀要）
- 2008年, 極域気水圏シンポジウムプログラム・講演要旨, 31st加速度データロガーを用いた飼育下キタオットセイの遊泳行動モニタリング
- 2007年, 平成19年度水産庁委託事業・多魚種資源管理調査事業報告書, <キタオットセイの摂餌生態に関する研究>(第2章) (第2章), 21 - 36データロガーを用いた飼育下キタオットセイの採餌行動モニタリング．
- 分担執筆, 亜南極の無人島でオットセイライフ p107-145, 東海大学出版部, 2016年12月はじめてのフィールドワーク②海の哺乳類編
- 分担執筆, オットセイは記憶力で採餌行動を決める p171-175, 京都通信社, 2016年08月バイオロギング＜２＞ 動物たちの知られざる世界を探る
- 分担執筆, 母の帰りを待ちわびて p62, 京都通信社, 2009年09月バイオロギング 最新科学で解明する動物生態学
- 独立行政法人環境再生保全機構, 環境研究総合推進費, 革新型研究開発, 神戸大学, 2022年04月 - 2025年03月, 研究代表者沿岸生態系の高次捕食動物スナメリ（絶滅危惧種）の生態解明
- 日本学術振興会, 科学研究費助成事業, 基盤研究(C), 東京大学, 2021年04月01日 - 2024年03月31日うるさい場所に慣れるか逃げるかー騒音がアオウミガメの性格分布に与える影響海中の騒音問題という新しい課題に対し、絶滅危惧種への影響・評価の指標を作り、人と動物が共存できる仕組みを作る必要がある。しかし、騒音は間接的な淘汰要因のため、移動性野生動物などの生態が不明瞭な絶滅危惧種では、生活史への影響・評価は難しい。そこで、本研究では、捕食圧が高いとリスクをとる個体は淘汰され、リスクを回避し続ける性格分布に偏る現象を利用し、騒音問題のある環境下でも同様の現象が起こっているか室内・野外実験で調べる。具体的には、まず、アオウミガメの性格であるBold―Shy分布を調べ、性格に応じて摂餌と逃避の時間配分が異なるか検証する。そして、性格に応じた野外行動と生息環境の特性を明らかにする。これにより、騒音がアオウミガメの行動を変え、性格分布を変えることが示されれば、騒音が淘汰圧として機能する指標として性格を用いることができる。 今年度は、性格を調べるための刺激の設定を行うために、複数の音刺激に対するプレイバック実験を行なった。その結果、全ての音刺激に対して、近づく個体と離れる個体が存在することがわかった。また、刺激を提示している時の心拍数は、刺激を提示しない時より多い傾向にあった。さらに、複数の音刺激の中でも特に、船舶音に対して心拍数が多くなる個体も確認された。今年度は個体数が少なく、傾向を見出すに止まったため、来年度は個体数を増やして刺激に対する反応を行動と心拍で特定し、反応の一貫性から性格を特定することを目指す。
- 公益財団法人市村清新技術財団, 地球環境研究助成, 2020年02月 - 2022年03月, 研究代表者気候変動が北極圏生態系に及ぼす影響を評価するための海生哺乳類の生態調査競争的資金
- 日本学術振興会, 科学研究費助成事業 研究活動スタート支援, 研究活動スタート支援, 東京大学, 2019年08月 - 2021年03月シロナガスクジラの保全に関する研究シロナガスクジラを含む大型ヒゲクジラ類の生態把握を目的とし、動物装着型記録計を用いた行動調査を実施した。2012-2021年の期間にアイスランドで得られたシロナガスクジラ6個体およびザトウクジラ14個体の行動データから、それぞれ1534回、6521回の潜水を記録が得られた。行動データから1潜水あたりの採餌イベント数の平均を年別に算出し、その採餌イベント数と水温（0m、20m、50m）の関係を調べたところ、採餌イベント数は深度50mの水温と負の相関が示された。調査海域に来遊するヒゲクジラ類は深度30-60m付近に分布する餌生物を採餌するため、深度50mの水温変化の影響を受けることが示唆された。
- クリタ水・環境科学振興財団, 自然科学・技術 (2), 2019年10月 - 2020年09月, 研究代表者南極定着氷下の水域生態系における高次捕食者の生態解明競争的資金
- 日本学術振興会, 科学研究費助成事業 若手研究(B), 若手研究(B), 東京大学, 2016年04月 - 2017年03月ヒゲクジラ類と漁業の競合問題を解決するためのカツオクジラの採餌行動の解明本研究ではナガスクジラ科の動物が必要とする資源量を推定するためにタイ湾でカツオクジラの摂餌量を実測することを目的とした。 2016年9月に野外調査準備として、動物装着型記録計（データロガー）、VHF発信器、浮力材と吸盤がセットになったタグを作製した。また既存のデータロガーは水中での抵抗が大きく、クジラへのタグ装着後すぐに外れてしまうという問題があったため、2016年8月に新規開発された小型のデータロガーを購入した。 2016年の10月29日から11月11日の期間、タイのサムットソンクラームに滞在しタイ湾で野外調査を実施した。例年では10-11月をピークとして、多くのカツオクジラがタイ湾に来遊するのだが、本調査ではクジラをほとんど見ることができなかった。例年よりも気温が低く、それが間接的にクジラの来遊状況に影響を与えていた可能性が考えられるが、はっきりとした理由はわからなかった。クジラにほとんど遭遇できなかったため、本調査ではクジラへのタグ装着はできなかった。野外調査においてタグ装着はできなかったが、滞在期間中にタイの共同研究者スラサク・トンサクディー研究員（Department of Marine and Coastal Resource）と本研究課題について多くの議論を交わすことができた。また今後の調査計画についての打ち合わせを実施した。 調査終了後はこれまで集めたデータおよび、今年度の調査で得られた目視観測のデータを合わせ解析を進め、現在国際学会誌への投稿準備中である。
- 京都大学野生動物研究センター, 共同利用・共同研究, 2015年04月 - 2016年03月, 研究代表者タイ沿岸域に来遊するニタリクジラの採餌行動の解明競争的資金
- 一般財団法人 自然環境研究センター, 公益信託乾太助記念動物科学研究助成基金, 2013年10月 - 2014年09月, 研究代表者北海道沿岸域に生息する絶滅危惧種ゼニガタアザラシの音響・行動生態に関する研究競争的資金
- 総合研究大学院大学, 海外学生派遣事業, 2007年07月, 研究代表者アイスランド沿岸域に来遊するミンククジラの生態調査競争的資金
研究シーズ
■ 研究シーズ- 南極・マクマード湾で繁殖するウェッデルアザラシの生態解明シーズカテゴリ：自然科学一般研究キーワード：動物生態, 行動, バイオロギング, 鰭脚類研究の背景と目的：生態系を理解するうえで高次捕食者の生態を明らかにすることは重要な項目の一つとして考えられています。南極海はウェッデルアザラシを高次捕食者とした生態系が形成されています。アザラシが氷上にいる間は観察することができるのですが、ひとたび海に潜ってしまうとアザラシが何をしているのかがわかりません。本研究ではウェッデルアザラシの水中での生態を明らかにすることを目的としました。研究内容：近年では直接観察することの難しい動物の生態を調べるために、バイオロギングと呼ばれる手法が使われています。バイオロギングとは動物に記録計を取り付け、動物の行動や周囲の環境を計測する手法です。野外調査は南極・マクマード湾で実施します。ウェッデルアザラシは、夏の期間（11-2月）に出産、子育てをし、子育て期間中の母アザラシは海洋でのエサ獲りと氷上での授乳を繰り返します。授乳のために氷上にいる母アザラシに記録計を装着し（図）、数日後に再び授乳のために氷上へ戻ってきた個体から記録計を回収します。本研究では、頭に加速度記録計とビデオ、背中に地磁気加速度記録計と音響記録計とビデオを取り付けます。頭の加速度記録計から餌取り行動、ビデオから餌の種類、背中に取り付けた地磁気加速度記録計から3次元遊泳軌跡、音響記録計から鳴音、ビデオから利用していた周囲の環境を明らかにします。
期待される効果や応用分野：ウェッデルアザラシの詳細な行動が明らかとなります。例えば餌採り回数や餌の種類から1日のエネルギー獲得量を見積もることができます。また、子育てに費やす時間から、自身の体調管理と子育てのトレードオフが明らかとなります。さらに、アザラシの鳴き声と行動データを照合することで、鳴音コミュニケーションを推察することができます。餌採りデータからアザラシの利用した海氷下の餌の分布を推定できるかもしれません。 - シロナガスクジラの生態に関する研究シーズカテゴリ：自然科学一般研究キーワード：動物生態, 行動生態, バイオロギング研究の背景と目的：地球上最大の動物であるシロナガスクジラは1900年代に世界中で捕鯨され、その個体数は激減し、現在ではIUCNレッドリストの絶滅危惧種として指定されています。動物を保護する上でまず初めに取り組むべき重要なことは、彼らの生態を理解することです。しかし、一生のうちほとんどの時間を水中で過ごすシロナガスクジラの生態的知見の多くが不足しているのが現状です。本研究ではシロナガスクジラの生態解明を目的とします。研究内容：本研究では観察することが難しいクジラの生態を調べるために、バイオロギングと呼ばれる動物に記録計を取り付ける手法を使います。野外調査はアイスランドで実施します。小型のボートでクジラに近づき、6メートルのポールを使って動物の背中に記録計を装着します（図）。取り付ける記録計は行動や音響を計測するものとビデオです。吸盤で装着するため、記録計は数時間から十数時間後に自然脱落します。記録計と一緒に取り付けた発信機の電波を頼りに脱落した記録計を回収します。回収した記録計からデータを取り出し、時系列解析ソフトを使い解析をします。餌を食べていたタイミングや休息していたタイミングをプログラミングによって抽出し、行動分類をします。また何を食べていたか、周りに他個体がいたかなどはビデオによりに確認できます。クジラの行動と鳴音を照合することで、クジラの鳴音の役割を考察します。
期待される効果や応用分野：シロナガスクジラの生態が明らかとなれば、個体数回復に向けて効果的な取り組みや適切な保護方法を立案できます。例えば、調査海域営まれているホエールウォッチングに対し、クジラの休息時間を避けた営業を推奨できます。クジラが餌捕りに使う海域や深度帯の知見は、漁業者がクジラとの競合を避けるために有益な情報となります。このように、本研究で得られる成果は、シロナガスクジラの保護に貢献できることが期待されます。
iwatatakashi
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