Dolphins 'smile' at each other while playing together.
Bottlenose dolphins 'smile' at each other
The animals are renowned for their playful nature and scientists in Italy have now realised how they use the 'open mouth' facial expression that is similar to a grin to communicate during social interaction.
Bottlenose dolphins typically adopt the expression when they are in their playmate's eyeline with the others responding with a 'smile' back a third of the time.
Dr. Elisabetta Palagi, senior author of the research at the University of Pisa, said: "We've uncovered the presence of a distinct facial display, the open mouth, in bottlenose dolphins, and we showed that dolphins are able to mirror others' facial expressions.
"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."