Most of the dolphin "smiles" were observed during playtime with other dolphins, rather than when they were interacting with their human trainers or playing alone. CNN
A new study has revealed that bottlenose dolphins may use a behavior similar to smiling during playtime to avoid misunderstandings. This open-mouthed expression, comparable to a human smile, was observed as a common communication tactic among dolphins, according to research published in a scientific journal. Researchers believe that this "smiling" behavior helps dolphins keep their playful interactions from escalating into conflicts.
The study was conducted by scientists from Italy and France, who observed 22 dolphins from two different locations—Zoomarine Rome and Planète Sauvage in France. The dolphins were seen playing with each other, their human trainers, and even by themselves. Interestingly, the study found that almost all of the smiles were exchanged when the dolphins were playing with one another, rather than with humans or alone. This suggests the smile-like expression is primarily a form of dolphin-to-dolphin communication.
When dolphins played together, they often flashed this open-mouth expression while in each other's view, and about a third of the time, the other dolphin would "smile" back. The researchers hypothesized that these expressions might serve as signals to prevent playful activities from turning into aggressive encounters due to misunderstandings. However, despite the similarity to a human smile, experts are cautious about interpreting it as the same.
Heather Hill, a dolphin communication expert and professor of psychology, agrees that the open-mouth response is likely a form of communication but isn't comfortable calling it a "smile." She pointed out that dolphins use this gesture in other contexts too, including aggressive or solitary situations, suggesting it may not always indicate pleasure like a human smile does. Hill further emphasized that it might simply be a way for dolphins to confirm they are on the same page during play, but we shouldn’t assume it has the same emotional significance as human smiles.
Dolphins are famous for their playful behavior, social lives, and complex communication. They enjoy various forms of play, such as leaping, breaching, tail-slapping, and play-fighting, often accompanied by vocalizations. Despite their reputation for being playful, researchers had never before studied their facial expressions during play. Other mammals, like humans and monkeys, have been observed using open-mouthed expressions during play as a form of communication, which scientists believe stems from a modified biting behavior.
In the study, researchers found that 92% of the dolphin smiles happened when they were interacting with one another, as opposed to playing with humans or on their own. No smiles were observed when the dolphins were engaging in aggressive behavior or more relaxed activities like swimming upside down or in parallel.
The researchers also noted the role of dolphin vocalizations during play, suggesting that future studies should focus on how sound and visual cues work together in dolphin communication. Dolphins are known to have one of the most complex vocal systems among animals, but their use of sound could expose them to predators. During play, dolphins likely use a mix of whistles and visual gestures to cooperate without being too worried about predators.
While this study focused on dolphins in captivity, Heather Hill believes that this smile-like behavior likely occurs in wild dolphins as well, though perhaps less frequently as wild dolphins are more focused on survival. The next step, according to Hill, would be to study wild dolphins using similar methods to understand if they communicate in the same way during play.
