酒井　麻衣 （サカイ　マイ）

コミュニケーション情報 byコメンテータガイド

• コメント

  イルカの社会行動、特にイルカ同士の接触を伴う行動や同調行動を、野生のイルカや水族館のイルカの行動を観察したり、イルカに記録計を取り付けたりして（バイオロギング）調べています。

• 報道関連出演・掲載一覧

  ＜報道関連出演・掲載一覧＞ ●2023/6/14 　京都新聞 　腹部斑点によるイルカの年齢推定方法の開発について ●2023/3/9 　毎日新聞 　腹部斑点によるイルカの年齢推定方法の開発について ●2023/2/9 　日刊工業新聞 　腹部斑点によるイルカの年齢推定方法の開発について ●2021/11/3 　フジテレビ「世界の何だコレ!?ミステリー 2時間スペシャル」 　「イルカのふれあい行動」について ●2021/10/20 　フジテレビ「世界の何だコレ!?ミステリー」 　シロイルカの行動について ●2020/11/7 　フジテレビ「めざましどようび」 　クジラの生態について ●2020/6/12 　テレビ朝日「ザワつく！金曜日」 　イルカのえさの取り方について ●2016/8/31 　NHK総合「ニュースシブ5時」 　野生イルカの調査や研究について ●2016/5/10 TBS系列「Nスタ ニューズアイ」 イルカの生態について ●2016/4/7 　読売テレビ「朝生ワイドす・またん！ZIP！」 　イルカの里親行動について ●2016/4/7 テレビ朝日「スーパーJチャンネル」 イルカの里親行動について ●2016/4/7 毎日放送「VOICE」 イルカの里親行動について ●2016/4/7 NHK総合「関西845～関西のニュースと気象情報～」 イルカの里親行動について ●2016/4/7 NHK総合「ニュース・気象情報」 イルカの里親行動について

研究者情報

学位

• 博士(理学)（東京工業大学）

ホームページURL

https://jglobal.jst.go.jp/detail?JGLOBAL_ID=201501007483864621

J-Global ID

• 201501007483864621

プロフィール

• 海棲哺乳類の社会・行動・認知や、環境エンリッチメントについて研究しています。

研究キーワード

• 個体群   社会行動   鯨類   認知科学   海洋動物   イルカ   動物行動学   ハクジラ亜目   コミュニケーション   左右性   Tursiops   ミナミハンドウイルカ   

現在の研究分野（キーワード）

イルカの社会行動、特にイルカ同士の接触を伴う行動や同調行動を、野生のイルカや水族館のイルカの行動を観察したり、イルカに記録計を取り付けたりして（バイオロギング）調べています。

研究分野

• ライフサイエンス / 水圏生命科学
• ライフサイエンス / 動物生理化学、生理学、行動学
• 人文・社会 / 認知科学
• ライフサイエンス / 水圏生産科学

経歴

• 2015年04月 - 現在  近畿大学農学部水産学科講師
• 2013年12月 - 2015年03月  東海大学創造科学技術研究機構日本学術振興会特別研究員(RPD)
• 2012年04月 - 2013年11月  京都大学野生動物研究センター日本学術振興会特別研究員(RPD)
• 2009年07月 - 2012年03月  東京大学生命科学ネットワーク特任助教
• 2008年04月 - 2009年06月  東京大学海洋研究所海洋科学国際共同研究センター特任研究員
• 2008年01月 - 2008年03月  University of PretoriaCetacean Unit, Mammal Research Institute, Department of Zoology and EntomologyPost-Doctoral Fellow
• 2005年10月 - 2008年03月  東京大学海洋研究所日本学術振興会特別研究員（PD）
• 2005年04月 - 2006年09月  東京工業大学 日本学術振興会特別研究員(DC)

学歴

• 2002年04月 - 2006年09月   東京工業大学大学院   生命理工学研究科   生体システム専攻
• 2000年04月 - 2002年03月   東京農工大学大学院   農学研究科   共生持続社会学専攻
• 1996年04月 - 2000年03月   東京農工大学   農学部   地域生態システム学科

所属学協会

• 日本バイオロギング研究会   勇魚会   日本哺乳類学会   日本水産学会   日本動物行動学会   国際海棲哺乳類学会   

研究活動情報

論文

• Observations and Detailed Descriptions of Sociosexual Behavior in Wild Indo-Pacific Bottlenose Dolphins (Tursiops aduncus)

  Aoi Miyanishi; Mai Sakai; Kazunobu Kogi

  Mammal Study 48 3 159 - 169 2023年05月 [査読有り]
  
• Noninvasive age estimation for wild Indo-Pacific bottlenose dolphins (Tursiops aduncus) using speckle appearance based on quantification-theory model I analysis

  Genfu Yagi; Kazunobu Kogi; Mai Sakai

  MARINE MAMMAL SCIENCE 39 2 662 - 670 2023年04月 [査読有り]
   

  Age is an important parameter for the study of ecology and population dynamics. Current methodologies for age estimation in cetaceans generally involve invasive or postmortem techniques. They are not suitable for wild marine mammals with small populations. Our previous study shows that in Indo-Pacific bottlenose dolphins, both the number and size of body speckles increase with age. We observed speckles of 41 known-age individuals (28 females and 13 males) between the ages of 7 and 25 years using underwater video data. The ages of individuals were obtained from a long-term identification survey since 1994. Here, we created an age-estimation model using quantification theory type I analysis. The model estimated the age accurately from speckle observation (R-2 = 0.77, standard deviation of 2.58 years). We clarified the age of 89 individuals (64% of 139 unknown age individuals) near Mikura Island. This is the first study to use a noninvasive age estimation method to statistically verify its accuracy and revealed the age of the majority of the population.
• Body length and growth pattern of free-ranging Indo-Pacific bottlenose dolphins off Mikura Island estimated using an underwater 3D camera

  Tadamichi Morisaka; Mai Sakai; Hiromitsu Hama; Kazunobu Kogi

  Mammalian Biology 2022年09月 [査読有り]
  
• Observations of flipper rubbing in mother-calf pairs of captive bottlenose dolphins (Tursiops truncatus) suggest a body-surface care function

  Mai Sakai; Hiroshi Katsumata; Shiro Kohshima

  JOURNAL OF ETHOLOGY 40 3 257 - 264 2022年06月 [査読有り]
   

  Bottlenose dolphins perform flipper rubbing in which they rub their partners with their pectoral fins. Considered similar to social grooming in primates, which have social and hygienic functions, flipper rubbing has been suggested to possess certain social functions. However, there are no reports based on quantitative data to support a hygienic function of this behavior. In this study, flipper rubbing and self-rubbing were observed in a group of three captive mother-calf dolphin pairs. In 19.2% of the observed 806 flipper-to-body rubbings and 54% of the 276 self-rubbings, dead skin was shed from the rubbed body part. There was a significant negative correlation between the number of flipper-to-body rubbing episodes the subjects received and their performance of self-rubbing. These results suggest that a function of flipper rubbing is to maintain and care for the body surface. In all mother-calf pairs, the mother rubbed her calf significantly more often than the calf rubbed the mother. Furthermore, each mother became a rubber significantly more often when their own offspring was their rubbing partner than when the partner was any other individual. These findings suggest that flipper rubbing is a mother-to-calf caring behavior.
• Age-related changes to the speckle patterns on wild Indo-Pacific bottlenose dolphins

  Genfu Yagi; Mai Sakai; Kazunobu Kogi

  MARINE MAMMAL SCIENCE 38 1 73 - 86 2022年01月 [査読有り]
   

  Age estimating wild dolphins using noninvasive methods will improve our understanding of their ontogeny. Speckles appear on the ventral through to the lateral areas of Indo-Pacific bottlenose dolphins (Tursiops aduncus) as they age. Age-related changes in the speckle density and shape were examined using type classification. Speckles first appeared on the ventral area of the genital area at approximately 6.5 years. They increased in two specific directions, from the genital area to the jaw and from the ventral side to the lateral side. The speckle shape changed with aging from a dot-shape to oblong. Individuals aged over 35 years possessed more speckles than those aged 24-26 years. The oldest age category of dolphins in this study was over 35 years. The speckling area similarly increased with age for all individuals. Therefore, the results suggest that speckle condition can be used to estimate age. The relationship between speckling area and age showed no significant sexual dimorphism except near the genital slit area. There was no speckle area around the genital slit which differed in shape between the sexes. Therefore, speckle patch shape may be a useful sex confirmation tool.
• The Passage Time of Prey Through the Digestive Tract of Indo-Pacific Bottlenose Dolphin (Tursiops aduncus)

  Rikiya TAKAHASHI; Nozomi KOBAYASHI; Suguru HIGA; Mai SAKAI

  Japanese Journal of Zoo and Wildlife Medicine 26 4 143 - 146 2021年12月 [査読有り]
  
• 飼育イロワケイルカの成熟オス・メスにおける社会行動の予備的分析

  長谷川雛; 酒井麻衣; 若林郁夫; 宮西葵

  哺乳類科学 61 2 197 - 203 2021年 [査読有り]
  
• 定住海域以外に出現したミナミハンドウイルカ様個体の種判別および種間交雑の可能性

  北夕紀; 佐々木萌美; 立川利幸; 十万仁志; 寺沢文男; 小木万布; 酒井麻衣; 村山美穂; 森阪匡通; 神田育子; 吉岡基

  DNA多型 29 1 2021年 [査読有り]
  
• Prey Species and Foraging Behaviour of Indo-Pacific Bottlenose Dolphins (Tursiops aduncus) Around Mikura Island in Japan

  Rikiya Takahashi; Mai Sakai; Kazunobu Kogi; Tadamichi Morisaka; Takao Segawa; Hiroshi Ohizumi

  Aquatic Mammals 46 6 531 - 541 2020年11月 [査読有り]
  
• Cooperation in bottlenose dolphins: bidirectional coordination in a rope-pulling task

  Chisato Yamamoto; Nobuyuki Kashiwagi; Mika Otsuka; Mai Sakai; Masaki Tomonaga

  PEERJ 7 2019年10月 

  In comparison with terrestrial animals, such as primates, there is limited empirical evidence for cooperative behavior in marine mammals under experimental conditions. In this study, we used a cooperative rope-pulling task to investigate how bottlenose dolphins (Tursiops truncatus) coordinate their behavior with a partner. Dolphins successfully learned and were able to perform the task, even when one subject started after the other. In the no-delay condition (i.e., both subjects sent at the same time), one pair of dolphins showed coordinated behaviors. When pairs were successful in solving the task in the delay condition (i.e., one individual sent later than the other), the initiators (i.e., first individual sent) were likely to wait for the follower to arrive, and the follower was likely to swim faster when the initiator did not wait and started pulling the rope alone. These coordinated behaviors might help resolve the given cooperative task. Our results suggest that bottlenose dolphins learn to coordinate their behaviors via trial and error and recognize the necessity of performing simultaneous actions with a partner to successfully accomplish cooperative tasks. In addition, both partners showed behavioral changes over many trials of no-delay and delay conditions, suggesting that bidirectional coordination occurred in the cooperative task.
• イルカの水中社会性：ふれあいと同調

  酒井麻衣

  哺乳類科学 58 1 135 - 139 2018年07月 [招待有り]
  
• Fluid dynamic effects of small projections based on dorsal ridge tubercles of the finless porpoise

  Yoshinobu INADA; Naoki TAMIYA; Maako MIYAKE; Tadamichi MORISAKA; Mai SAKAI; Ikuo WAKABAYASHI; Masahiko KASAMATSU; Yasuhiro UEKUSA

  Journal of Biomechanical Science and Engineering 12 3 2017年07月 [査読有り]
  
• 御蔵島に生息するミナミハンドウイルカ(Tursiops aduncus)の親子鑑定

  北夕紀; 村山美穂; 小木万布; 森阪匡通; 酒井麻衣; 椎名隆

  DNA多型 25 1 52‐57 - 57 2017年07月 [査読有り]
  
• 並走する流線型物体の間に働く流体力学的効果の分析

  三宅 真亜子; 奈良 祥太朗; 稲田 喜信; 高橋 俊; 酒井 麻衣; 森阪 匡通

  日本航空宇宙学会論文集 65 1 27 - 31 一般社団法人 日本航空宇宙学会 2017年 [査読有り]
   

  Fluid dynamic effects between adjacent streamline bodies have a conspicuous role in drag reduction. One typical example is a dolphin drafting. When two dolphins such as a mother and a calf swim side by side, the calf seldom flaps its tail fin, indicating the calf utilizes the fluid dynamic force between the two bodies as a thrust. This force is generated by the Venturi effect. In this study, wind tunnel tests were conducted with two streamline bodies of different sizes that mimicked the mother and the calf dolphins to clarify the fluid dynamic effects between two bodies at various relative positions. In consequence, the increase of friction drag by the acceleration of flow between two bodies and the thrust generation by the Venturi effect were confirmed as well as the optimum position to maximize the thrust, indicating the possibility of effective design of airplanes with external appendages.
• Emigration of Indo-Pacific bottlenose dolphins (Tursiops aduncus) from Mikura Island, Japan

  Kimika Tsuji; Kazunobu Kogi; Mai Sakai; Tadamichi Morisaka

  Aquatic Mammals 43 6 585 - 593 2017年 [査読有り]
   

  © Aquatic Mammals 2017. Emigration of individual animals is an important biological phenomenon that depends on both populations and ecosystem attributes. Off Mikura Island, a long-term identification survey of individual Indo-Pacific bottlenose dolphins has been conducted since 1994 using an underwater video system. Between 1994 and 2014, 277 individual dolphins were identified by this survey, with 41 individuals emigrating from Mikura Island during this period. Adults emigrated significantly more often than younger age classes. The sex and age classes of emigrants in 2008 and 2010 (the years with the greatest amount of emigration) differed, suggesting that social relationships within a population may affect emigration. Emigrants were observed among the Izu Island Chain and in Chiba, Shizuoka, Mie, and Wakayama Prefectures. The greatest distance dolphins emigrated from Mikura Island was 390 km to Tanabe in Wakayama Prefecture. Some individuals were observed to have emigrated to several areas during the period. The most frequent destination was Toshima Island, one of the Izu Islands Chain, where emigrants have been observed to reproduce. Emigrant groups were composed exclusively of individuals from Mikura Island; there were no immigrants to the Mikura Island area during the 20-y period of observation, although six emigrants eventually returned to their original range. Future studies of social relationships and habitat use by emigrants will reveal more about the reasons dolphins leave their habitats.
• A wild Indo-Pacific bottlenose dolphin adopts a socially and genetically distant neonate

  Mai Sakai; Yuki F. Kita; Kazunobu Kogi; Masanori Shinohara; Tadamichi Morisaka; Takashi Shiina; Miho Inoue-Murayama

  SCIENTIFIC REPORTS 6 23902  2016年04月 [査読有り]
   

  Alloparental behaviour and adoption have been reported in many mammals and birds. Such behaviours are energetically costly, and their causes and functions remain unclear. We observed the adoption behaviour of a wild Indo-Pacific bottlenose dolphin (Tursiops aduncus) near Mikura Island, Japan. A calf was seen with its mother on six observation days. Following the mother's death, the calf was observed with a sub-adult female on all 18 observation days from May to September 2012. On three days, the calf was observed swimming with this female in the suckling position and milk was seen leaking from the female's mammary slit. A five-year dataset revealed no significant social or kin relationships between the biological mother and allomother, indicating that kinship and social relationships did not play an important role in the observed adoption.
• A Simple and Non-invasive Measurement Method Important for Conserving Large Animals Underwater

  Tadamichi Morisaka; Mai Sakai; Kazunobu Kogi; Hiromitsu Hama

  GENETIC AND EVOLUTIONARY COMPUTING, VOL I 387 105 - 111 2016年 [査読有り]
   

  This paper shows how simple, non-invasive measurement method is important for conserving large animals living underwater. We have studied free-ranging wild Indo-Pacific bottlenose dolphins (Tursiops aduncus) around Mikura Island, Japan for about 15 years. We usually observe dolphin behavior and record acoustics underwater including photo-identification of every dolphins. Despite lots of video data, more basic information such as body size have lacked. In order to measure body size of the animals non-invasively, we used commercial measurement software which can measure the distance between two points on 3D photos by commercial 3D camera. Accuracy evaluation tests using a tape measure between 15 and 250 cm were conducted at the field site (Mikura Island) and the errors were within 5 % of the actual sizes. We successfully measured body size of 33 free-ranging wild dolphins. Mean absolute percentage error of the same individuals in different photos was within 4 % for dolphins. The average size of the adult dolphins was 249.6cm, which was the similar to the average actual size of 4 by-caught dolphins of the population (251.7 cm). We also opportunistically measured green turtles (Chelonia mydas) during our dolphin survey. Mean absolute percentage error of the same individuals in different photos was within 2 % for turtles. The average straight carapace length (SCL) of the 14 turtles was 48.3 cm (37.9 - 67.7 cm), which is much smaller than the adult green turtle length (80 - 111 cm). A simple measurement method is thus important to know the size of the large animals underwater, which indicates animal age and health condition, and are important for conserving these large animals.
• Detection of the Nighttime Distribution of Indo-Pacific Bottlenose Dolphins (Tursiops aduncus) around Mikura Island with Stationed Acoustic Buoys

  MORISAKA Tadamichi; SAKAI Mai; SAKAI Mai; KOGI Kazunobu

  東海大学海洋研究所研究報告(Web) 36 1‐7 (WEB ONLY)  2015年03月
• Investigation of a Flow in Dolphin Drafting by Computational Fluid Dynamics

  NARA Shotaro; MIYAKE Maako; TAKAHASHI Shun; INADA Yoshinobu; SAKAI Mai; MORISAKA Tadamichi

  Proceedings. International Conference on Flow Dynamics (CD-ROM) 12th 152‐153  2015年
• Sound variation and function in captive Commerson's dolphins (Cephalorhynchus commersonii).

  Yayoi M Yoshida; Tadamichi Morisaka; Mai Sakai; Mari Iwasaki; Ikuo Wakabayashi; Atsushi Seko; Masahiko Kasamatsu; Tomonari Akamatsu; Shiro Kohshima

  Behavioural processes 108 11 - 9 2014年10月 [査読有り]
   

  Commerson's dolphin (Cephalorhynchus commersonii), one of the smallest dolphin species, has been reported to produce only narrow-band high-frequency (NBHF) clicks and no whistles. To clarify their sound repertoire and examine the function of each type, we analysed the sounds and behaviour of captive Commerson's dolphins in Toba Aquarium, Japan. All recorded sounds were NBHF clicks with peak frequency >110kHz. The recorded click-trains were categorised into four types based on the changing pattern of their Inter-click intervals (ICI): Decreasing type, with continuously decreasing ICI during the last part of the train; Increasing type, with continuously increasing ICI during the last part; Fluctuating type, with fluctuating ICI; and Burst-pulse type, with very short and constant ICI. The frequency of the Decreasing type increased when approaching an object newly introduced to the tank, suggesting that the sound is used for echolocation on approach. The Burst-pulse type suddenly increased in front of the object and was often oriented towards it, suggesting that it was used for echolocation in close proximity to the object. In contrast, the Increasing type was rarely recorded during approach, but increased when a dolphin approached another dolphin. The Increasing and Burst-pulse types also increased when dolphins began social behaviours. These results suggest that some NBHF clicks have functions other than echolocation, such as communication.
• Sound variation and function in captive Commerson's dolphins (Cephalorhynchus commersonii)

  Yayoi M. Yoshida; Tadamichi Morisaka; Mai Sakai; Mari Iwasaki; Ikuo Wakabayashi; Atsushi Seko; Masahiko Kasamatsu; Tomonari Akamatsu; Shiro Kohshima

  BEHAVIOURAL PROCESSES 108 11 - 19 2014年10月 [査読有り]
   

  Commerson's dolphin (Cepholorhynchus commersonii), one of the smallest dolphin species, has been reported to produce only narrow-band high-frequency (NBHF) clicks and no whistles. To clarify their sound repertoire and examine the function of each type, we analysed the sounds and behaviour of captive Commerson's dolphins in Toba Aquarium, Japan. All recorded sounds were NBHF clicks with peak frequency >110 kHz. The recorded click-trains were categorised into four types based on the changing pattern of their Inter-click intervals (ICI): Decreasing type, with continuously decreasing ICI during the last part of the train; Increasing type, with continuously increasing ICI during the last part; Fluctuating type, with fluctuating ICI; and Burst-pulse type, with very short and constant ICI. The frequency of the Decreasing type increased when approaching an object newly introduced to the tank, suggesting that the sound is used for echolocation on approach. The Burst-pulse type suddenly increased in front of the object and was often oriented towards it, suggesting that it was used for echolocation in close proximity to the object. In contrast, the Increasing type was rarely recorded during approach, but increased when a dolphin approached another dolphin. The Increasing and Burst-pulse types also increased when dolphins began social behaviours. These results suggest that some NBHF clicks have functions other than echolocation, such as communication. (C) 2014 Elsevier B.V. All rights reserved.
• A Mobile Measurement System for Sound Source Level of Wild Dolphin Whistles

  Morisaka Tadamichi; Sakai Mai; Kogi Kazunobu; Shinke Tomio; Zin Thithi; Hama Hiromitsu

  Memoirs of the Faculty of Engineering Osaka City University 54 54 25 - 29 大阪市立大学 2013年12月
• Body contact and synchronous diving in long-finned pilot whales

  Kagari Aoki; Mai Sakai; Patrick J. O. Miller; Fleur Visser; Katsufumi Sato

  BEHAVIOURAL PROCESSES 99 12 - 20 2013年10月 [査読有り]
   

  Synchronous behavior, as a form of social interaction, has been widely reported for odontocete cetaceans observed at the sea surface. However, few studies have quantified synchronous behavior underwater. Using data from an animal-borne data recorder and camera, we described how a pair of deep-diving odontocetes, long-finned pilot whales, coordinated diving behavior. Diving data during overlapping periods of 3.7 h were obtained from two whales within a stable trio. The tagged whales made highly synchronous movements, and their dive durations differed only slightly (3 +/- 3 s). The pair of whales maintained a constant and narrow vertical separation (ca. 3 m) throughout synchronous dives. The overall fluking rate for the same travel speed during synchronous dives was virtually the same as that during asynchronous dives, suggesting that synchronous behavior did not affect locomotion effort. In addition, a possible affiliative behavior was recorded by the animal-borne camera: another individual appeared in 8% of the frames, both with and without body contact to the tagged whale. The primary type of body contact was flipper-to-body. Our study, the first on underwater synchronous behavior and body contact of pilot whales, highlights the utility of using animal-borne devices for enabling new insights into social interactions. (C) 2013 Elsevier B.V. All rights reserved.
• Mother–calf interactions and social behavior development in Commerson’s dolphins (Cephalorhynchus commersonii)

  Mai Sakai; Tadamichi Morisaka; Mari Iwasaki; Yayoi Yoshida; Ikuo Wakabayashi; Atsushi Seko; Masahiko Kasamatsu; Shiro Kohshima

  Journal of Ethology 31 3 305 - 313 2013年09月 [査読有り]
   

  Mother-calf interactions and the behaviors of mothers during separation from their calves were examined in four Commerson's dolphin (Cephalorhynchus commersonii) mother-calf pairs. Four infants were observed: 56.8 h over 30 days from birth to 263 days of age, 36.9 h over 20 days from birth to 149 days of age, 10.4 h over 3 days from birth to 2 days of age, and 15.0 h over 3 days from birth to 2 days of age. All four pairs shared common characteristics in the rate and frequencies of mother-calf interactions and the behaviors of mothers during the first week of life. After the first week, individual differences in changes in the frequency of each behavior were observed. The three behaviors considered representative of maternal care (parallel swimming, synchronous breathing, and body-to-body contact) were frequently performed in the first week; thereafter, the frequencies declined. Separate behaviors of mothers were infrequent during the first week and increased with an increase in infants' age. Bumping by infants increased with time, suggesting an increase in soliciting by calves and conflict between mothers and calves. The frequency of flipper-to-body rubbing also changed but in a complex manner, probably because the calves needed to learn how to perform this behavior from their mothers and because initiator and recipient of this behavior can be changed quickly. © 2013 Japan Ethological Society and Springer Japan.
• Spontaneous Ejaculation in a Wild Indo-Pacific Bottlenose Dolphin (Tursiops aduncus)

  Tadamichi Morisaka; Mai Sakai; Kazunobu Kogi; Akane Nakasuji; Kasumi Sakakibara; Yuria Kasanuki; Motoi Yoshioka

  PLOS ONE 8 8 e72879  2013年08月 [査読有り]
   

  Spontaneous ejaculation, which is defined as the release of seminal fluids without apparent sexual stimulation, has been documented in boreoeutherian mammals. Here we report spontaneous ejaculation in a wild Indo-Pacific bottlenose dolphin (Tursiops aduncus), and present a video of this rare behavior. This is the first report of spontaneous ejaculation by an aquatic mammal, and the first video of this behavior in animals to be published in a scientific journal.
• イルカと泳ぐ : 適切な「イルカ観」と持続可能なイルカスイムに向けて (特集 2012年度関西シンポジウム ヒトと動物の関わり : 癒しから治療へ)

  森阪 匡通; 酒井 麻衣; 小木 万布

  ヒトと動物の関係学会誌 = Japanese journal of human animal relations 35 23 - 27 ヒトと動物の関係学会 2013年07月
• ミナミハンドウイルカの識別個体から得た鳴音の音源音圧のバリエーション

  森阪 匡通; 酒井 麻衣; 小木 万布; 新家 富雄

  霊長類研究 Supplement 29 0 106 - 106 日本霊長類学会 2013年 

   ミナミハンドウイルカ (Tursiops aduncus) の鳴音，特にホイッスルに関する音響的・行動学的な研究は多くなされている．しかし彼らが実際にどのくらいの音圧で鳴音を発しているのかに関しては，水中という環境で研究することの困難さから情報が不足している．音源音圧は鳴音がどのくらいの距離で届くのかといった重要な情報をもたらすため，音声コミュニケーションの研究はもとより，船舶のエンジン音の影響など保全を考える上では必須である．本研究では識別された個体の発する鳴音の音源音圧を推定することを目的とし，そのバリエーションについて考えたい．2012年 9月から 10月に伊豆諸島御蔵島にて新規に開発した水中マイクアレー・ビデオシステムを用いてミナミハンドウイルカと併泳しながらその鳴音を収録した．複数の識別個体からホイッスル音を複数回取得した結果，ホイッスルの音源音圧はイルカの位置や姿勢によって影響を受けていることがわかった．つまり腹部中心が見える位置で録音したホイッスルは，それ以外に比べ音圧が低く，かつ倍音成分が消える．これはホイッスルが噴気孔付近あるいは頭部上方から発せられているためであると考えられる．イルカに対する録音場所も意識しながら録音・解析を行う必要があることがわかった．なお本研究は科研費基盤Ｂ (23310166) 『野生イルカ個体群保全のための非侵襲的計測手法の開発』による成果である．
• 自己鏡映像認知への温故知新

  草山太一; 池田譲; 入江尚子; 陳香純; 坪川達也; 武野純一; 酒井麻衣

  動物心理学研究 62 1 111-124 (J-STAGE) - 124 THE JAPANESE SOCIETY FOR ANIMAL PSYCHOLOGY 2012年
• Do Porpoises Choose Their Associates? A New Method for Analyzing Social Relationships among Cetaceans

  Mai Sakai; Ding Wang; Kexiong Wang; Songhai Li; Tomonari Akamatsu

  PLOS ONE 6 12 e28836  2011年12月 [査読有り]
   

  Background: Observing and monitoring the underwater social interactions of cetaceans is challenging. Therefore, previous cetacean studies have monitored these interactions by surface observations. However, because cetaceans spend most of their time underwater, it is important that their underwater behavior is also continuously monitored to better understand their social relationships and social structure. The finless porpoise is small and has no dorsal fin. It is difficult to observe this species in the wild, and little is known of its sociality. Methodology/Principal Findings: The swim depths of 6 free-ranging finless porpoises were simultaneously recorded using a time-synchronized bio-logging system. Synchronous diving was used as an index of association. Two pairs, # 27 (an immature female estimated to be 3.5 years old) and # 32 (an adult male), # 28 (a juvenile male estimated to be 2 years old) and # 29 (an adult male), tended to participate in long periods of synchronized diving more frequently than 13 other possible pairs, indicating that the 4 porpoises chose their social partners. The adult males (# 32, # 29) tended to follow the immature female (# 27) and juvenile male (# 28), respectively. However, during synchronized diving, the role of an initiator often changed within the pair, and their body movements appeared to be non-agonistic, e. g., rubbing of bodies against one another instead of that on one-side, as observed with chasing and escaping behaviors. Conclusions/Significance: The present study employed a time-synchronized bio-logging method to observe the social relationships of free-ranging aquatic animals based on swimming depth. The results suggest that certain individuals form associations even if they are not a mother and calf pair. Long synchronized dives occurred when particular members were reunited, and this suggests that the synchronized dives were not a by-product of opportunistic aggregation.
• Reactions of Heaviside’s dolphins to tagging attempts using remotely-deployed suction-cup tags

  Mai Sakai; Leszek Karczmarski; Tadamichi Morisaka; Meredith Thornton

  South African Journal of Wildlife Research 41 1 134 - 138 2011年04月 [査読有り]
   

  Tagging attempts of Heaviside's dolphins (Cephalorhynchus heavisidii) using a remotely-deployed suction-cup tag were performed in Table Bay and St Helena Bay on the southwest coast of South Africa. The observed reactions of dolphins indicate that this tagging approach has negligible impacts on the dolphin behaviour and Heaviside's dolphins might be tagged with suction cup tags without adverse affects.
• Swim speed and acceleration measurements of short-finned pilot whales (Globicephala macrorhynchus) in Hawai‘i

  Mai Sakai; Kagari Aoki; Katsufumi Sato; Masao Amano; Robin W. Baird; Daniel L. Webster; Gregory S. Schorr; Nobuyuki Miyazaki

  Mammal Study 36 1 55 - 59 2011年03月 [査読有り]
  
• Echolocation signals of Heaviside's dolphins (Cephalorhynchus heavisidii)

  Tadamichi Morisaka; Leszek Karczmarski; Tomonari Akamatsu; Mai Sakai; Steve Dawson; Meredith Thornton

  JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 129 1 449 - 457 2011年01月 [査読有り]
   

  Field recordings of echolocation signals produced by Heaviside's dolphins (Cephalorhynchus heavisidii) were made off the coast of South Africa using a hydrophone array system. The system consisted of three hydrophones and an A-tag (miniature stereo acoustic data-logger). The mean centroid frequency was 125 kHz, with a -3 dB bandwidth of 15 kHz and -10 dB duration of 74 mu s. The mean back-calculated apparent source level was 173 dB re 1 mu Pa(p.-p.). These characteristics are very similar to those found in other Cephalorhynchus species, and such narrow-band high-frequency echolocation clicks appear to be a defining characteristic of the Cephalorhynchus genus. Click bursts with very short inter-click intervals (up to 2 ms) were also recorded, which produced the "cry" sound reported in other Cephalorhynchus species. Since inter-click intervals correlated positively to click duration and negatively to bandwidth, Heaviside's dolphins may adjust their click duration and bandwidth based on detection range. The bimodal distribution of the peak frequency and stable bimodal peaks in spectra of individual click suggest a slight asymmetry in the click production mechanism. (C) 2011 Acoustical Society of America. [DOI: 10.1121/1.3519401]
• Acoustic behavior of captive Commerson’s dolphins (Cephalorhynchus commersonii).

  Yoshida Y; Morisaka T; Sakai M; Iwasaki M; Wakabayashi I; Seko A; Kasamatsu M; Fukuzawa H; Akamatsu T; Kohshima S

  The 15th Kyoto University International Sym-posium: Biodiversity, Zoos and Aquariums “The Message from Animals” (2010/09, Nagoya). 2010年 [査読有り]
  
• Fine-scale analysis of synchronous breathing in wild Indo-Pacific bottlenose dolphins (Tursiops aduncus)

  Mai Sakai; Tadamichi Morisaka; Kazunobu Kogi; Toru Hishii; Shiro Kohshima

  BEHAVIOURAL PROCESSES 83 1 48 - 53 2010年01月 [査読有り]
   

  We quantitatively analysed synchronous breathing for dyads in Indo-Pacific bottlenose dolphins at Mikura Island. Tokyo, Japan. For most cases, we observed dyads swimming in the same direction (97%). in close proximity (i.e., less than 1.5 m) and with their body axes parallel as they breathed synchronously. Moreover, the pairs engaged in identical behaviour before and after the synchronous breathing episodes. These results suggest that the dolphins synchronize their movements, and that synchronous breathing is a component of "pair-swimming", an affiliative social behaviour. Same sex pairs of the same age class frequently engaged in synchronous breathing for adults and subadults, as well as mother-calf and escort-calf pairs. The distance between individuals during synchronous breathing for mother-calf pairs was less than for other pairs. The distance observed between individuals for female pairs was less than for male pairs. The time differences between each exhale for each of the two dolphins involved in synchronous breathing episodes for female pairs were smaller than for male pairs, and time differences for adult pairs were smaller than subadult pairs. These results suggest that age and sex class influenced the characteristics of this behaviour. (C) 2009 Elsevier B.V. All rights reserved.
• 飼育個体の観察から何がわかるか? : サル, イルカ, マメジカ, サイの事例から

  幸島 司郎; 小林 洋美; 久世 濃子; 関口 雄祐; 荒井 一利; 酒井 麻衣; 岩崎 真里; 松林 尚志; 喜安 薫

  哺乳類科学 48 1 159 - 167 The Mammal Society of Japan 2008年06月
• Flipper rubbing behaviors in wild bottlenose dolphins (Tursiops aduncus)

  Mai Sakai; Toru Hishii; Shohei Takeda; Shiro Kohshima

  MARINE MAMMAL SCIENCE 22 4 966 - 978 2006年10月 [査読有り]
   

  "Flipper rubbing" behavior was quantitatively analyzed in wild Indo-Pacific bottlenose dolphins (Tursiops aduncus) around Mikura Island, Tokyo, Japan. We observed two types of flipper rubbing: (1) F-B rubbing; one dolphin (Rubber) rubbed its flipper over various parts of a partner's (Rubbee) body, and (2) F-F rubbing; both dolphins rubbed each other's anterior flipper edge in alternating shifts. F-B rubbings tended to be initiated by the Rubbee and were terminated by the Rubber. The Rubbee often moved actively its body part that was in contact with the Rubber's flipper, and assumed side-up, upside-down, or other postures while the Rubber remained horizontal in most cases. These facts suggest that the Rubbee engaged in F-B rubbing more actively than the Rubber, and might receive some benefit from the frictional contact during F-B rubbing. Dolphins often switched their roles as Rubber and Rubbee between episodes of flipper rubbing bout. Adults and sub-adults exchanged F-B rubbing and F-F rubbing most often with individuals of the same sex in the same age class. F-B rubbing was frequent in mother-and-calf dyads. Our results suggest that flipper rubbing is an affiliative behavior which could be a quantitative measure of social relationships among individuals of this species in future studies.
• Laterality of flipper rubbing behaviour in wild bottlenose dolphins (Tursiops aduncus): Caused by asymmetry of eye use?

  M Sakai; T Hishii; S Takeda; S Kohshima

  BEHAVIOURAL BRAIN RESEARCH 170 2 204 - 210 2006年06月 [査読有り]
   

  To determine whether wild Indo-Pacific bottlenose dolphins (Tursiops aduncus) at Mikura Island, Japan, show asymmetry of eye or flipper use during a social behaviour, we investigated the laterality of flipper-to-body (F-B) rubbing, in which one dolphin ("rubber") rubs the body of another ("rubbee") with its flipper. We analysed 382 episodes of video-recorded F-B rubbings performed by identified individuals (N= 111 rubbers). F-B rubbing was conducted significantly more frequently with the left flipper than with the right flipper. The duration of F-B rubbings was also significantly longer with the left flipper than with the right flipper. Of 20 dolphins, nine individuals showed significant left-side bias as the rubber in this behaviour, whereas no dolphins showed significant right-side bias. The results indicate a population-level left-side bias of the rubber in F-B rubbing. An analysis of the swimming configurations during this behaviour suggests that the asymmetry in F-B rubbing was caused not only by the laterality of the rubber, but by a preference for use of the left eye in both dolphins during this behaviour. Dolphins used the left eye significantly more frequently than the right eye during the inquisitive behaviour, while they showed no significant bias in flipper use during the object-carrying behaviour. These facts also suggest that the asymmetry of F-B rubbing is caused by the preference for using the left eye. Significant left-side bias was observed only in F-B rubbings initiated by the rubbee, in which the rubbee determined its position during this behaviour. This suggests that this behavioural asymmetry was enhanced by the rubbees choosing the left side of the rubber to ensure better and longer rubs. (c) 2006 Elsevier B.V. All rights reserved.
• Behavioural observations of bottlenose dolphins towards two dead conspecifics

  Kathleen. M. Dudzinski; Mai Sakai; Keiko Masaki; Kazunobu Kogi; Toru Hishii; Michio Kurimoto

  29 108 - 116 2003年 [査読有り]
  

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