Published: June 12, 2021
共同利用・共同研究 本研究は、京都大学野生動物研究センター共同利用研究制度を利用しておこなわれました。


Yawn-like behavior in captive common bottlenose dolphins (Tursiops truncatus)

Akiko Enokizu, Tadamichi Morisaka, Katsushi Murakami, Natsuko Sakurai, Nahoko Ueda, Motoi Yoshioka

DOI: 10.1016/j.beproc.2021.104444
Yawning is an involuntary action that begins with a slow opening of the mouth with inhalation, followed by a maximum gaping phase, and ends with a short exhalation and the closing of the mouth. A wide variety of vertebrate species, including humans, yawn. Here, we report underwater yawn-like behavior in three captive common bottlenose dolphins, inferred from 119-h of observations. Five cases of yawn-like behavior were selected out of 2045 open-mouth behaviors, after removing intentional open-mouth behaviors. Yawn-like behaviors were chosen that had a mouth open–close duration ratio of ≤ 1 (duration of Phase 3, the period of mouth closing after maximum opening, divided by the duration of Phase 1, the period of mouth opening from start to maximum opening). Naïve human evaluators selected “yawn-like” behaviors. All five cases of yawn-like behavior occurred during inactive periods, similar to human yawns. In three of the five cases, inactivity levels significantly decreased within 4 min after the yawn-like behavior; therefore, yawn-like behavior in dolphins may increase their arousal level in drowsy states. Thus, the yawn-like behavior of dolphins, without breathing, is similar to yawning in terrestrial animals, including humans.
朝日新聞「イルカが水中であくび 大学院生が14日間観察し発見」など
Article Information
Enokizu, A., Morisaka, T., Murakami, K., Sakurai, N., Ueda, N., & Yoshioka, M.(2021)Yawn-like behavior in captive common bottlenose dolphins (Tursiops truncatus) Behavioural Processes , 189: 10444 10.1016/j.beproc.2021.104444