Bottlenose dolphins smile at each other when they play – new study reveals how and why

Dolphins have an irresistible fascination for people. Regardless of their age, they are very playful and often play by themselves, riding waves, jumping into the air, doing flips, and slapping the water with their tail fins.

They also play with anything they find in the ocean, including sponges, corals, sticks, plastic bags, and floating buoys.

Their play is also social. Bottlenose dolphins (Tursiops truncatus) live in temperate and tropical waters around the world, including off the coast of Africa, and play with other dolphins during their first few weeks of life. The mother dolphin becomes the first playmate, and the young dolphin then expands its social network. This species of dolphin is an ideal model for studying how animals communicate through play.

When we humans see a relaxed, open-mouthed facial expression, we automatically imitate it within milliseconds. This is called rapid facial mimicry. It’s a reflex, and you start moving without thinking. In humans and many other animals, rapid facial mimicry helps synchronize movements during play.

Until now, the role of facial communication in managing dolphin-dolphin play encounters has remained a mystery. Our research revealed that bottlenose dolphins have a unique facial feature: an open mouth. This expression is most commonly observed during playful interactions with other dolphins, especially when the sender is within the receiver’s line of sight.

Our findings shed new light on how dolphins use subtle facial cues during social play.

sophisticated communication

Dolphins rely heavily on visual cues to navigate their social and physical world. However, facial expressions are very difficult to study due to the limited movement of facial muscles.

However, the playful social behavior of dolphins and the way they signal each other’s field of vision is similar to that of other mammals. This suggests that dolphins may use facial expressions to convey information.

Certain environments prefer certain methods of passing messages. Dolphins communicate through one of the most complex vocal systems in the animal kingdom. They use high-pitched whistles to recognize each other and interact socially. This probably evolved because they live in murky waters with poor visibility and have no choice but to rely on sound. However, sound can also expose them to predators and eavesdroppers.

We also already knew that dolphins can shift to visual communication when they’re in clear water or when they get close to each other. This led us to speculate that facial expressions may be important for rapid two-way interactions.

When dolphins play together, a combination of whistles and visual cues helps them work together to accomplish goals. This strategy is especially useful during social play when alertness to predators is low.

Previous studies have shown that when dolphins communicate with other species, they are very interested in whether their audience is paying attention. This suggests that they are aware of the recipient’s focus and adjust their behavior accordingly. It highlighted their advanced communication abilities that go beyond mere audio signals.

What the smiles of about 1,300 dolphins told us

We photographed 22 captive dolphins for 80 hours over 60 days. During this time, 837 free play sessions were held. During these play sessions, the dolphins performed acrobatics on their own and also played with humans, other species, and other dolphins.

A total of 1,288 open-mouth events and smiling dolphins were recorded.

Studying dolphin visual communication in a controlled environment has provided insight into their subtle interactions. However, our study also had limitations because the dolphins we studied were not free.

In the future, research using wild dolphins may be conducted. This will require the use of artificial intelligence, observing how dolphins see each other (eye tracking), and ultrasound recordings. This will increase our understanding of diverse forms of communication and the differences between dolphins playing with each other and other species.

New discovery: Dolphins imitate each other’s smiles

We were surprised to discover that dolphins not only open their mouths and show facial expressions when playing, but they can also mirror other people’s facial expressions.

The discovery of rapid facial mimicry in dolphins is one of the striking findings of this study. No one knew that this mimicry existed in dolphins.

Given that dolphins frequently engage in the same activities and situations, we investigated whether dolphins simply happened to imitate each other’s open-mouthed facial expressions.

However, they found that if the recipient dolphin saw the original facial expression, they were 13 times more likely to imitate another dolphin’s open mouth within one second. The animals increased their open-mouth displays primarily after recognizing other animals doing the same thing.

This rate of imitation in dolphins has also been observed in certain carnivores, such as meerkats and sun bears.

They also investigated the question of whether dolphins open their mouths to prepare for a bite, rather than as a signal. However, in more than a third of the cases (33.16%), these dolphin smiles elicited a similar open-mouthed response from the recipient.

In the remaining 66.84% of cases, the recipient did not smile back and the first dolphin did not bite the playmate. This suggests that this behavior may have evolved from a bite prevention strategy to a form of communication, with the original function translated into a social signal.

Cetacea (whales, dolphins, and porpoises) are closely related to artiodactyls (a group of mammals that includes deer, camels, wild boars, hippos, etc.). These native relatives have not been extensively studied for play communication. But exploring these connections can provide insight into how communication evolved.

We are still discovering the evolutionary origins of play and how animals fine-tune their play behaviors. But one thing is clear. The open-mouth signal and rapid imitation appear repeatedly throughout the mammalian family tree.

This suggests that visual communication has played an important role in shaping complex social interactions, not only in dolphins but in many species.

This article is republished from The Conversation under a Creative Commons license. Read the original article.