They are widely considered to be one of the most charismatic animals in the ocean.
Now a new study shows that bottlenose dolphins actually ‘smile’ at each other while surfing, hunting and playing.
Until now, little is known about how the species – famous for their intelligence and playfulness – interact during play.
But experts have finally revealed that these dolphins use the ‘open mouth’ facial expression (similar to a smile) to communicate during social play.
The dolphins use the facial expression almost always when they are in their playmate’s field of view, the researchers found, and playmates responded by “smiling” back a third of the time.
They are widely considered to be one of the most charismatic animals in the ocean. Now a new study shows that bottlenose dolphins actually ‘smile’ at each other while surfing, hunting and playing.
“We discovered the presence of a distinct facial expression, the open mouth, in bottlenose dolphins, and we showed that dolphins are also able to mirror the facial expression of others,” senior author and evolutionary biologist Elisabetta Palagi, from the University of Pisa, said.
‘Open mouth signals and rapid mimicry appear repeatedly in the mammalian family tree, indicating that visual communication has played a crucial role in shaping complex social interactions, not only in dolphins but over time in many species.’
Dolphin play can include acrobatics, surfing, playing with objects, hunting and play fighting.
To investigate whether dolphins visually convey playfulness, the researchers recorded captive bottlenose dolphins while they were playing in pairs and while they were playing freely with their human trainers.
They showed that dolphins often use the open-mouthed expression when playing with other dolphins, but that they do not appear to use this expression when playing with people or when playing alone.
Experts have finally revealed that these dolphins use the ‘open mouth’ facial expression (similar to a smile) to communicate during social play.
Dr. Palagi said that while some may argue that dolphins only imitate each other’s mouth expressions by chance, this “does not explain why the probability of imitating another dolphin’s open mouth in one second is 13 times greater if the recipient actually sees the original expression.” . ‘
Although only one open-mouth event was recorded during solitary play, the researchers recorded a total of 1,288 “smiles” during social play sessions, and 92 percent of these events occurred during dolphin-dolphin play sessions.
Dolphins were also more likely to adopt the open-mouthed expression when their faces were in their playmate’s field of view, and the team witnessed the playmate “smile” back 33 percent of the time.
Dr. Palagi said that while some may argue that dolphins only imitate each other’s mouth expressions by chance, this “does not explain why the probability of imitating another dolphin’s open mouth in one second is 13 times greater if the recipient actually sees the original expression.” . .’
The researchers did not record the dolphins’ acoustic signals during play, and they say future studies should investigate the possible role of vocalizations and tactile signals during playful interactions.
“This degree of mimicry in dolphins is consistent with what has been observed in certain carnivores, such as meerkats and sun bears,” she added.
“The relaxed open mouth seen in social carnivores, the playful faces of monkeys, and even human laughter, is a universal sign of playfulness, allowing animals (and us) to signal pleasure and avoid conflict.”
The researchers did not record the dolphins’ acoustic signals during play, and they say future studies should investigate the possible role of vocalizations and tactile signals during playful interactions.
“Future research should delve into eye-tracking to investigate how dolphins see their world and use acoustic cues in their multimodal communication during play,” says corresponding author and zoologist Livio Favaro.
‘Dolphins have developed one of the most complex vocal systems in the animal kingdom, but noise can also expose them to predators or eavesdroppers.
‘When dolphins play together, a mix of whistles and visual cues help them work together and achieve goals, a strategy that is especially useful during social play, when they are less wary of predators.’
The findings have been published in the journal iScience.