Emily Chan
They found that 92 percent of the open-mouth expressions occurred when the dolphins were playing with each other. Only one open-mouth event was recorded during solitary play.
The dolphins were also more likely to use facial expressions when their playmates could see their faces—89 percent of recorded open-mouth events happened in this context. When the “smile” was perceived, the playmate “smiled” back 33 percent of the time.
“Some may argue that dolphins are merely mimicking each other’s open-mouth expressions by chance, given they’re often involved in the same activity or context, but this doesn’t explain why the probability of mimicking another dolphin’s open mouth within one second is 13 times higher when the receiver actually sees the original expression,” said Palagi.
It is unclear exactly what the behavior means or why the dolphins are “smiling.” The research team also doesn’t know if a “smile” means the same thing to dolphins as it does to humans.
Other animals, such as meerkats, orangutans, wolves, and cats, have been observed making similar faces, but that does not necessarily connect to a specific emotion or mood.
The researchers did not record the dolphins’ acoustic signals during playtime. It is possible that the dolphins were simply opening their mouths to make vocalizations.
In addition, the study focused on captive dolphins. So, future research should look into the role vocalizations play during social interactions and whether wild dolphins “smile” at each other.
The study was published in the journal iScience.
