Dolphins are identified for what look like massive, contagious smiles. However do they really, nicely, smile?

The reply, in response to a brand new examine of dolphin play, is a convincing “possibly.” Dolphins use their smile-like facial features when interacting with their mates throughout playful instances, researchers report October 2 in iScience. That, the staff says, suggests the cetaceans are doing one thing akin to a human chuckle. However different specialists urge warning in attributing humanlike conduct to creatures whose intent we will solely guess at.

Scientists have lengthy identified anecdotally that dolphins can show a conduct referred to as “open mouth,” which individuals usually affiliate with a smile. Different animals, like primates, could make an identical relaxed open mouth to speak throughout playful contexts (SN: 6/10/15). “It’s a sign that communicates, ‘Look, I’m simply taking part in!’,” says Elisabetta Palagi, a comparative ethologist on the College of Pisa in Italy. “Like after we put a smiley face on a mobile phone message that might be deceptive.”

Nonetheless, such conduct has by no means been studied in-depth in dolphins. So Palagi and colleagues recorded practically 900 play classes amongst 22 captive bottlenosed dolphins (Tursiops truncatus), filming practically 1,300 “smiles” from 17 animals. The researchers filmed dolphins taking part in alone, with different dolphins and with people.

The dolphins primarily confirmed their open-mouth conduct whereas taking part in with a companion, often one other dolphin, the staff discovered. When the animals had been taking part in alone, they virtually by no means did. Moreover, about 90 p.c of open-mouth expressions had been carried out when the dolphins had been of their playmate’s discipline of view.

Additionally, when one in every of these “smiles” was seen by one other dolphin, in a few third of instances, the receiver additionally “smiled” again in lower than a second. That, Palagi says, is identical time that elapses between a human perceiving a facial features after which mirroring it.  

The outcomes counsel that the dolphin’s open-mouth expression is “a really subtle type of communication,” Palagi says, which is perhaps used along with acoustic indicators (SN: 12/7/17). Whereas it’s onerous to say whether or not it had the identical evolutionary origin as people’ smile, it most likely has “the identical perform,” for the reason that context and the best way by which it happens is identical as in people, she says.

“With the ability to see some proof that’s demonstrating [dolphin’s open-mouth behavior] in a play context is admittedly nice,” says animal behavioralist Erin Frick, who was not concerned with the examine. However, she provides, dolphins use mouth opening in different contexts as nicely, resembling displaying a risk in an aggressive context. “I don’t suppose open mouths are at all times speaking play. I feel they do have a job in play,” says Frick, of Eckerd Faculty in St. Petersburg, Fla.

However Palagi is satisfied the open mouth is devoted solely to playful contexts: When the dolphins in her examine had been performing aggressively, her staff didn’t see the animals performing this specific open-mouth conduct. “Through the few aggressions we witnessed, we noticed the opening of the mouth, however after this extraordinarily fast opening, both a chunk or an tried chunk adopted.”

Regardless, Frick just isn’t able to name the conduct a smile. “It’s not the identical,” she says. “However it nonetheless has a really … purposeful kind in how they convey.”

Like Frick, comparative psychologist Heather Hill additionally urges warning in decoding the obvious smiles. “I’m not tremendous snug calling it a ‘smile,’ provided that delphinids and whales use the open mouth show in quite a lot of social contexts,” says Hill, of St. Mary’s College in San Antonio.

Palagi is cognizant of the hesitancy. “There’s a sturdy debate if in nonhuman animals, the act of smiling or laughing … is pushed by emotional arousal or intention,” she says. “We had been extraordinarily conservative and easily referred to facial show”.

Palagi provides, “It’s not simple to say if [the open mouth] in dolphins conveys an emotional temper or is used to easily talk to others, ‘Hey, don’t be scared, I’m simply taking part in!’, or each.” One factor the staff needs to research is whether or not the presence of open-mouth conduct alters play classes in any manner. Maybe “laughing collectively” — if that’s certainly what it’s — makes the dolphins play collectively longer.