Research activity information

• Biologging intelligent Platform (BiP): an integrated and standardized platform for sharing, visualizing, and analyzing biologging data

  Katsufumi Sato, Shinichi Watanabe, Takuji Noda, Takuya Koizumi, Ken Yoda, Yuuki Y. Watanabe, Kentaro Q. Sakamoto, Teijiro Isokawa, Makoto A. Yoshida, Kagari Aoki, Akinori Takahashi, Takashi Iwata, Hideaki Nishizawa, Takuya Maekawa, Ryo Kawabe, Yutaka Watanuki

  Springer Science and Business Media LLC, Apr. 2025, Movement Ecology, 13(1) (1)

  [Refereed]

  Scientific journal


• Biologging as a potential platform for resolving ocean environmental issues and threats: Towards the development of the Internet of Animals

  Takashi Iwata, Tomonari Akamatsu

  Elsevier BV, Mar. 2025, Water Biology and Security, 100383 - 100383

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Prey targeted by lactating Weddell seals (Leptonychotes weddellii) in Erebus Bay, Antarctica

  Rose T. N. Foster-Dyer, Kimberly T. Goetz, Takashi Iwata, Rachel R. Holser, Sarah A. Michael, Craig Pritchard, Simon Childerhouse, Daniel P. Costa, David G. Ainley, Matthew H. Pinkerton, Michelle A. LaRue

  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, Aug. 2024, Polar Biology

  [Refereed]

  Scientific journal


• Detection of environmental DNA of finless porpoise (Neophocaena asiaeorientalis) in Osaka Bay, Japan

  Nagisa Hashimoto, Takashi Iwata, Natsumi Kihara, Kiyomi Nakamura, Masayuki K. Sakata, Toshifumi Minamoto

  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.

  Corresponding, Springer Science and Business Media LLC, May 2024, Conservation Genetics Resources

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Non‐lunge feeding behaviour of humpback whales associated with fishing boats in Norway

  Takashi Iwata, Kagari Aoki, Patrick J. O. Miller, Martin Biuw, Michael J. Williamson, Katsufumi Sato

  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, Nov. 2023, Ethology

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• First observations of Weddell seals foraging in sponges in Erebus Bay, Antarctica

  Rose T. N. Foster-Dyer, Kimberly T. Goetz, Matthew H. Pinkerton, Takashi Iwata, Rachel R. Holser, Sarah A. Michael, Craig Pritchard, Simon Childerhouse, Jay Rotella, Luisa Federwisch, Daniel P. Costa, Michelle A. LaRue

  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, May 2023, Polar Biology, 46(7) (7), 611 - 621

  [Refereed]

  Scientific journal


• Similar circling movements observed across marine megafauna taxa

  Tomoko Narazaki, Itsumi Nakamura, Kagari Aoki, Takashi Iwata, Kozue Shiomi, Paolo Luschi, Hiroyuki Suganuma, Carl G. Meyer, Rui Matsumoto, Charles A. Bost, Yves Handrich, Masao Amano, Ryosuke Okamoto, Kyoichi Mori, Stéphane Ciccione, Jérôme Bourjea, Katsufumi Sato

  Elsevier BV, Mar. 2021, iScience, 24(4) (4), 102221 - 102221

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Using an omnidirectional video logger to observe the underwater life of marine animals: humpback whale resting behaviour

  Takashi Iwata, Martin Biuw, Kagari Aoki, Patrick James O’Malley Miller, Katsufumi Sato

  Feb. 2021, Behavioural Processes, 186, 104369 - 104369, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Aerial photogrammetry and tag-derived tissue density reveal patterns of lipid-store body condition of humpback whales on their feeding grounds

  Kagari Aoki, Saana Isojunno, Charlotte Bellot, Takashi Iwata, Joanna Kershaw, Yu Akiyama, Lucía M. Martín López, Christian Ramp, Martin Biuw, René Swift, Paul J. Wensveen, Patrick Pomeroy, Tomoko Narazaki, Ailsa Hall, Katsufumi Sato, Patrick J. O. Miller

  Jan. 2021, Proceedings of the Royal Society B: Biological Sciences, 288(1943) (1943), 20202307 - 20202307, English

  [Refereed]

  Scientific journal


• Utilization and development of biologging in marine mammal studies

  Takashi Iwata

  Aug. 2020, Mammalian Science, 60(2) (2), 281 - 296, Japanese

  [Refereed]

  Scientific journal


• Leave or stay? Video-logger revealed foraging efficiency of humpback whales under temporal change in prey density.

  Yu Akiyama, Tomonari Akamatsu, Marianne H Rasmussen, Maria R Iversen, Takashi Iwata, Yusuke Goto, Kagari Aoki, Katsufumi Sato

  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, PloS one, 14(2) (2), e0211138, English, International magazine

  [Refereed]

  Scientific journal


• Future directions in research on Bryde’s whales

  Constantine R, Iwata T, Nieukirk S.L, Penry G

  Sep. 2018, Frontiers in Marine Science, 5, 333, English

  [Refereed]

  Scientific journal


• Tread-water feeding of Bryde's whales

  Takashi Iwata, Tomonari Akamatsu, Surasak Thongsukdee, Phaothep Cherdsukjai, Kanjana Adulyanukosol, Katsufumi Sato

  Nov. 2017, CURRENT BIOLOGY, 27(21) (21), R1154 - R1155, English

  [Refereed]

  Scientific journal


• The influence of preceding dive cycles on the foraging decisions of Antarctic fur seals

  T. Iwata, K. Q. Sakamoto, E. W. J. Edwards, I. J. Staniland, P. N. Trathan, Y. Goto, K. Sato, Y. Naito, A. Takahashi

  Jul. 2015, BIOLOGY LETTERS, 11(7) (7), 20150227, English

  [Refereed]

  Scientific journal


• Heart rate and estimated energy expenditure of flapping and gliding in black-browed albatrosses

  Kentaro Q. Sakamoto, Akinori Takahashi, Takashi Iwata, Takashi Yamamoto, Maki Yamamoto, Philip N. Trathan

  Aug. 2013, JOURNAL OF EXPERIMENTAL BIOLOGY, 216(16) (16), 3175 - 3182, English

  [Refereed]

  Scientific journal


• Detection of grooming behaviours with an acceleration data logger in a captive northern fur seal (Callorhinus ursinus)

  Takashi Iwata, Shiroh Yonezaki, Kaoru Kohyama, Yoko Mitani

  Lead, 2013, Aquatic Mammals, 39(4) (4), 378 - 384, English

  [Refereed]

  Scientific journal


• Report of seabird observation in the Indian sector of the Southern Ocean during the austral summer of 2005-2008.

  Iwata. T, Hayashi. T, Takasawa-Kasamatsu. N

  2013, Czech Polar Reports, 3, 82 - 86

  [Refereed]


• Using a mandible accelerometer to study fine-scale foraging behavior of free-ranging Antarctic fur seals

  Takashi Iwata, Kentaro Q. Sakamoto, Akinori Takahashi, Ewan W. J. Edwards, Iain J. Staniland, Philip N. Trathan, Yasuhiko Naito

  Apr. 2012, MARINE MAMMAL SCIENCE, 28(2) (2), 345 - 357, English

  [Refereed]

  Scientific journal


• Scaling of swim speed in breath-hold divers

  Yuuki Y. Watanabe, Katsufumi Sato, Yutaka Watanuki, Akinori Takahashi, Yoko Mitani, Masao Amano, Kagari Aoki, Tomoko Narazaki, Takashi Iwata, Shingo Minamikawa, Nobuyuki Miyazaki

  Jan. 2011, JOURNAL OF ANIMAL ECOLOGY, 80(1) (1), 57 - 68, English

  [Refereed]

  Scientific journal


• Validation of acceleration records to monitor swimming and prey-capture behavior in the captive northern fur seal

  Takashi Iwata, Yoko Mitani, Shiroh Yonezaki, Kaoru Kohyama, Akinori Takahashi

  Nov. 2009, NIPPON SUISAN GAKKAISHI, 75(6) (6), 989 - 994, Japanese

  [Refereed]

  Scientific journal


• From the Eye of the Albatrosses: A Bird-Borne Camera Shows an Association between Albatrosses and a Killer Whale in the Southern Ocean

  Kentaro Q. Sakamoto, Akinori Takahashi, Takashi Iwata, Philip N. Trathan

  Oct. 2009, PLOS ONE, 4(10) (10), e7322, English

  [Refereed]

  Scientific journal

• Biologging intelligent Platform（BiP）により実現する バイオロギングデータの共有と海洋の可視化

  渡辺 伸一, 野田 琢嗣, 小泉 拓也, 依田 憲, 吉田 誠, 岩田 高志, 西澤 秀明, 奥山 隼一, 青木 かがり, 木村 里子, 坂本 健太郎, 高橋 晃周, 前川 卓也, 楢崎 友子, 三田村 啓理, 佐藤 克文

  Apr. 2022, 日本生態学会誌, 73(1) (1), 1 - 9


• タイ湾のカツオクジラ調査

  岩田高志

  2017, 勇魚, 65, 18 - 22

  [Invited]


• Plankton sampling by the training vessel Umitaka-maru in the Indian sector of the Southern Ocean in the austral summer of 2012/2013.

  Sakurai. H, Uchiyama. K, Shimada K, Iwata. T, Takasawa. N, Watanabe. H, Ono. A, Tachibana. A, Mitazaki. N, Ojima. M, Kitade. Y, Moteki. M, Ishimaru. T, Takahashi. T. K, Iida. T, Makabe. R, Odate. T, Tanimura. A

  2016, JARE DATA REPORTS (Marine Biology), 56, 1 - 20

  Report research institution


• 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

  岩田高志, 三谷曜子, 三谷曜子, 米崎史郎, 香山薫, 高橋晃周, 高橋晃周

  2008, 極域気水圏シンポジウムプログラム・講演要旨, 31st


• 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．

  岩田高志, 三谷曜子, 米崎史郎, 香山薫, 伊豆三津シーパラダイス海獣チーム, ショーチーム

  2007, 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

• はじめてのフィールドワーク②海の哺乳類編

  岩田高志

  Contributor, 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, Dec. 2016


• バイオロギング＜２＞ 動物たちの知られざる世界を探る

  岩田高志

  Contributor, 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, Aug. 2016


• バイオロギング 最新科学で解明する動物生態学

  岩田高志

  Contributor, 母の帰りを待ちわびて p62, 京都通信社, Sep. 2009

• 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

  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, Apr. 2022 - Mar. 2025, Principal investigator


• Avoid or acclimate ? The Effects of noise on personality traits of green sea turtles in coastal habitat.

  工藤 宏美, 岩田 高志, 楢崎 友子, 奥山 みなみ

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), The University of Tokyo, 01 Apr. 2021 - 31 Mar. 2024

  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。


• 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

  公益財団法人市村清新技術財団, 地球環境研究助成, Feb. 2020 - Mar. 2022, Principal investigator

  Competitive research funding


• Study on the conservation of blue whales

  Iwata Takashi

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Research Activity start-up, Grant-in-Aid for Research Activity start-up, The University of Tokyo, Aug. 2019 - Mar. 2021

  To reveal ecology of large baleen whales including blue whales, we investigated behaviour of baleen whales using animal-borne data loggers. Behavioural data of 6 blue whales and 14 humpback whales in Iceland during 2012-2022 periods were obtained. 1534 dives from blue whales and 6521 dives from humpback whales were recorded. The average number of foraging events per dive was calculated yearly from the behavioural data. The relationship between the number of foraging events and the water temperature (0m, 20m, 50m depth) was investigated. The relationship between number of foraging events and the water temperature at a depth of 50 m was shown negative correlation. It was suggested that baleen whales in the survey area are affected by changes in water temperature at a depth of 50 m because they forage prey species distributed in a depth of 30-60 m.


• 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

  岩田高志

  クリタ水・環境科学振興財団, 自然科学・技術 (2), Oct. 2019 - Sep. 2020, Principal investigator

  Competitive research funding


• 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

  岩田 高志

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B), Grant-in-Aid for Young Scientists (B), The University of Tokyo, Apr. 2016 - Mar. 2017

  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。


• タイ沿岸域に来遊するニタリクジラの採餌行動の解明

  岩田高志

  京都大学野生動物研究センター, 共同利用・共同研究, Apr. 2015 - Mar. 2016, Principal investigator

  Competitive research funding


• 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

  岩田高志

  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, Oct. 2013 - Sep. 2014, Principal investigator

  Competitive research funding


• 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

  岩田高志

  総合研究大学院大学, 海外学生派遣事業, Jul. 2007, Principal investigator

  Competitive research funding