(CNN) – For humans, smiling is an easy way to avoid misunderstandings. And, according to a new study, bottlenose dolphins may use a similar tactic when playing with each other.
The study published Wednesday in the journal iScience found that dolphins make an open-mouth expression, comparable to a “smile,” during their play.
To carry out the research, a group of scientists from institutions in Italy and France observed 11 dolphins in the Zoomarine oceanarium in Rome and another 11 in the Planète Sauvage animal park, in western France, playing with each other, with their trainers. and alone.
The researchers found that the marine mammals “smiled” almost always when they were in their playmate’s field of view, and their playmate “smiled back” a third of the time. This suggests that this is a form of communication, they said, hypothesizing that by “smiling” at each other, the dolphins could prevent their games from turning into a real fight due to a communication breakdown.
But although their expression resembles a smile to humans, dolphin communication expert Heather Hill, a professor of psychology at St. Mary’s University in San Antonio, Texas, who was not involved in the study, cautions against excessive extrapolation.
“I think dolphins engage in an open-mouth response during play situations, and it seems reasonable that it is a form of communication. “I don’t feel comfortable calling it a smile, because they also use an open mouth in many other contexts,” she told CNN, pointing out its use in aggressive, solitary and playful acts.
“Should we interpret it simply as an exchange of open mouths that occurs between two individuals to communicate ‘hey, we’re on the same page,’” he added. “Does that necessarily mean that because it is a game it is enjoyable and therefore you and I smile at each other like a human or a chimpanzee would? “I’m not sure I’m ready to take that next step.”
Dolphins, much loved and anthropomorphized by humans, are known for their playful nature, their rich social life and the complex communication between them. They have many different ways of playing together, such as jumping or tumbling over the water, hitting the surface of the water with their tail fins, fighting while playing, or surfing through the waves.
But despite dolphins’ playful reputation, their facial expressions during play have never been investigated before, although studies have established that other mammals, such as humans and monkeys, communicate with smile-like open-mouth expressions when playing. they play Scientists widely believe this behavior stems from a modified biting action without actual contact, according to the study.
Researchers in the latest study found that 92% of the cases in which dolphins used the open-mouth expression occurred when they were playing with each other, rather than with humans or alone.
When the dolphins were engaged in an aggressive interaction or a more relaxing activity, such as parallel or upside-down swimming, the scientists did not observe the “smiling” expression.
The researchers also highlighted the importance of the dolphins’ vocal communication during their play, and said this could be a focus for future studies, since they did not record these signals.
“Dolphins have developed one of the most intricate vocal systems in the animal world, but sound can also expose them to predators or spies,” corresponding author Livio Favaro, a zoologist at the University of Turin, said in a statement.
“When dolphins play together, a combination of whistles and visual cues helps them cooperate and achieve goals, a particularly useful strategy during social play when they are less on guard against predators,” he added.
All dolphins observed for this study live in captivity. Hill noted that “smiling” behavior probably also occurs in the wild, but perhaps less frequently, as they spend more time searching for food and avoiding predators.
“The next step would be to apply the same methodology, work with those wild species and observe and see what they are doing in the same type of context,” he said.
