Observation of yawn-like behavior in a dugong (Dugong dugon)

Yawning is an involuntary action that occurs in three phases: (1) slow mouth opening accompanied by inhalation, (2) maintaining the maximum mouth size, and (3) quick closure with exhalation. Yawning is a phylogenetically widespread behavior in vertebrates. Here, we report yawn-like behavior in a captive dugong. Fourteen yawn-like behaviors were identified in a 20.1 h observation period. These yawn-like behaviors occurred significantly more during resting states than during more active states. These yawn-like behaviors of the dugong may function as yawns, typically associated with drowsiness. These findings imply that yawning may be a universal behavior, even in fully aquatic mammals.