Bottlenose Dolphins Smile At Each Other While Playing, Making Open-Mouth Facial Expressions To Communicate During Social Interactions

While bottlenose dolphins are playing together, they “smile” at each other, making “open-mouth” facial expressions as a way to communicate during social interactions. The dolphins almost always use facial expressions when they are in their playmate’s field of vision.
When the dolphins perceived a “smile,” they would respond with one themselves 33 percent of the time. The new findings may help scientists learn more about the evolution of mammals, including humans.
“Open-mouth signals and rapid mimicry appear repeatedly across the mammal family tree, which suggests that visual communication has played a crucial role in shaping complex social interactions, not only in dolphins but in many species over time,” said Elisabetta Palagi, a study co-author and an evolutionary biologist at the University of Pisa in Italy.
Dolphin play involves acrobatics, surfing, chasing, play-fighting, and playing with objects. Other mammals use facial expressions to communicate socially during playtime, but the behavior had never been explored in marine mammals before.
Researchers noticed that bottlenose dolphins (Tursiops truncatus) living in captivity typically made open-mouth facial expressions while playing together.
However, they did not seem to “smile” in other situations. So, they wanted to investigate whether the dolphins visually communicated playfulness.
They captured 80 hours of video footage of 22 bottlenose dolphins while they were playing in pairs and while they were playing with their human trainers.
The dolphins lived at two wildlife parks: Zoomarine Rome in Italy and Planète Sauvage in France.
After analyzing the recordings, the researchers counted a total of 1,288 open-mouth displays during social play sessions.

skvalval – stock.adobe.com – illustrative purposes only, not the actual dolphin
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.
Sign up for Chip Chick’s newsletter and get stories like this delivered to your inbox.
More About:Animals