By Stephen Beech via SWNS
Bottlenose dolphins “smile” at each other while playing, reveals new research.
The “open mouth” expression probably evolved from biting, say scientists exploring how marine mammals communicate during playtime.
They found that bottlenose dolphins use facial expressions – similar to a smile – to communicate during social play.
The dolphins almost always use facial expressions when they are in their playmate’s field of view, according to the findings published in the journal iScience.
And when playmates perceived a “smile” they responded in kind 33% of the time, say the Italian research team.
Study senior author Dr. Elisabetta Palagi said: “We’ve uncovered the presence of a distinct facial display, the open mouth, in bottlenose dolphins, and we showed that dolphins are also able to mirror others’ facial expression.
“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.”
She says dolphin play can include acrobatics, surfing, chasing, and playfighting, and it’s important that the activities aren’t misinterpreted as aggression.
Other mammals use facial expressions to communicate playfulness, but whether marine mammals also use facial expressions to signal playtime hasn’t been previously explored.
Dr. Palagi, an evolutionary biologist at the University of Pisa, said: “The open mouth gesture likely evolved from the biting action, breaking down the biting sequence to leave only the ‘intention to bite’ without contact.
“The relaxed open mouth, seen in social carnivores, monkeys’ play faces, and even human laughter, is a universal sign of playfulness, helping animals – and us – signal fun and avoid conflict.”
To investigate whether dolphins visually communicate playfulness, the researchers recorded captive bottlenose dolphins as they played in pairs and while they were playing freely with their human trainers.
The team showed that dolphins frequently use the open-mouth expression when playing with other dolphins, but they don’t seem to use it when playing with humans or when they’re playing by themselves.
While only one open-mouth event was recorded during solitary play, the researchers recorded a total of 1,288 open-mouth events during social play sessions, and 92% of those events occurred during dolphin-dolphin play sessions.
Dolphins were also more likely to assume the open-mouth expression when their faces were in the field of view of their playmate, with 89% of recorded open-mouth expressions emitted in that context.
When the “smile” was perceived, the playmate smiled back 33% of the time.
Dr. Palagi said: “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.”
She added: “This rate of mimicry in dolphins is consistent with what’s been observed in certain carnivores, such as meerkats and sun bears.”
The research team says that future studies should investigate the possible role of vocalizations and tactile signals during playful dolphin interactions.
Study corresponding author Dr. Livio Favaro, of the University of Torino, said: “Future research should dive into eye-tracking to explore how dolphins see their world and utilize acoustic signals in their multimodal communication during play.”
He added: “Dolphins have developed one of the most intricate vocal systems in the animal world, but sound can also expose them to predators or eavesdroppers.
“When dolphins play together, a mix of whistling and visual cues helps them cooperate and achieve goals, a strategy particularly useful during social play when they’re less on guard for predators.”
