Dolphins are beloved amongst researchers and laypeople alike. These charming cetaceans have, for as long as we've known of them, fascinated us with their intelligence, playfulness and complex social lives. With their acrobatic leaps, their intricate whistles and the fascinating clicks they use to communicate, dolphins continue to surprise researchers with just how intriguing their everyday lives are.
A groundbreaking new discovery (as of October 2024) has revealed an unexpected and endearing behavior in bottlenose dolphins that underpins their playful interactions -- and hints at just how deeply they bond with one another. Beyond deepening our understanding of their social lives, this finding also emphasizes the fact that, in many ways, the gap between humans and dolphins might not be as wide as we think.
Play, for humans, is an integral part of well-being and development -- from early childhood, and even in adulthood. Given that it requires imagination, coordination and collaboration, it serves as an indescribably important way for us to develop our physical, emotional, social and mental skills. This, in many ways, applies similarly to the animal kingdom -- including marine mammals.
Generally, any behavior that serves purely enrichment purposes -- as opposed to meeting survival needs -- can be described as play for animals, according to a 2015 study from Current Biology. Specifically, this entails behaviors that are intrinsically fun and rewarding to the animal, and are always spontaneous, voluntary and, most importantly, intentional.
However, it's worth noting that what may look like play isn't always a playful interaction, which is a departure that applies to almost any animal. Some instances of chasing, hitting and jumping may look like fun and games to us humans, but -- in many cases -- it usually serves an evolutionary purpose. Nevertheless, for dolphins in particular, play is still incredibly common -- and it comes in various shapes and sizes, according to the abovementioned study:
Bottlenose dolphins are happy to engage in these many forms of play, either in solitude or with others. In the early stages of life, they're more likely to play either alone or with their mothers, according to 2014 research from Animal Behavior and Cognition.
Yet, as they grow older, bottlenose dolphins' play becomes increasingly social; they become braver, and in turn, more likely to initiate said playful interactions themselves.
Most fascinatingly, dolphins have recently been observed using specific facial expressions to signal their interest in playful interactions, according to an October 2024 study from iScience. In particular, bottlenose dolphins will "smile" at each other during these moments.
According to the study, this "smile" involves a wide open mouth -- a gesture believed to have evolved from biting behavior. During play, however, it seems to convey a lack of aggression and, instead, an explicit intent for pure playfulness.
"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," explains one of the authors of the study, Dr. Elisabetta Palagi, in an interview with SciNews.
Specifically, the researchers recorded a grand total of 1,288 open-mouth displays amongst bottlenose dolphins in interactive, social play settings -- 92% of which were dolphin-dolphin events. More fascinatingly, this behavior was most commonly exhibited when the dolphin's playmate could see it, suggesting the smile to be an intentional, friendly gesture. And, most sweetly, if the playmates recognized the smile, they returned it around 33% 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," explains Dr. Palagi in her interview. "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."
Overall, this finding demonstrates the universality of playfulness as a language -- one that, evidently, transcends species. As we continue, even today, to learn more about the rich lives of dolphins, one sentiment becomes clear: these charismatic mammals aren't so different from us; their world is just as full of joy, connection and fun as ours. In their open-mouthed expressions of joy, we've come to recognize echoes of our own laughter -- our own ways of sharing delight with those we care about.