Bottlenose dolphins 'smile' to say it's time to play

[Judi Lynn]

Similar light-hearted open mouth expressions can also be seen on primates–like us.
By Laura Baisas

Posted on Oct 2, 2024 11:00 AM EDT

Dolphins are among the most playful and social animals on Earth, yet we don’t know much about how they communicate during games and other more light interactions. New research of captive bottlenose dolphins (Tursiops truncates) indicates that they use an “open mouth” facial expression similar to a smile to communicate during social play. This expression was most consistently used when a dolphin is in their playmate’s field of view and some respond with a similar expression. The findings are detailed in a study published October 2 in the Cell Press journal iScience.

For dolphins, play can include acrobatics, surfing, playing with objects, chasing, and playfighting. These activities may appear aggressive to humans, but generally are not. Other mammals, including primates, use facial expressions to communicate playfulness, but it was not clear if marine mammals also use their facial expressions to do this.

“I spent a lot of years studying play across different species, and Livio [Favaro] and I wanted to start studying play in dolphins too,” Elisabetta Palagi, a study co-author and comparative ethologist at the University of Pisa, tells Popular Science.

In the study, Palagi and Favaro–a University of Turin marine biologist–recorded video of 22 captive bottlenose dolphins in four social groups. They took footage while the dolphins were playing in pairs, solo, and with their human trainers.

“After recording the first videos we realized that dolphins emitted prolonged open mouth displays while playing and we did not see a similar behavior in any other context,” says Palagi. “Open mouth is not a bite. During an open mouth expression, the subject never tries to bite the playmate.”

More:
https://www.popsci.com/environment/dolphins-smile-play/