Why do dolphins smile? New findings are astonishing

The friendly facial expression is an innate anatomical characteristic in dolphins: it actually says nothing about the emotional state of the animals. They supposedly still smile even when they are severely stressed or in severe pain.

However, according to a study, the marine mammals tend to open their mouths while playing, making it appear as if they are openly laughing at the other person. The expression is mainly used if the playmate in question can see it, the research team reports in the journal ‘iScience’.

The scientists led by Elisabetta Palagi from the University of Pisa have now observed bottlenose dolphins (Tursiops truncatus), which love to play. They filmed and analyzed how captive animals played with each other, alone or with their trainers.

Can mirror peers
Accordingly, bottlenose dolphins exhibit an expression called “open mouth” mainly during social play with other dolphins or – less commonly – humans, and almost never during solo play. If the playmate could see the opened snout, he often opened his too – which to people seems like the animals are happily laughing at each other. The results showed, on the one hand, that the open mouth expression also occurs in dolphins, and on the other hand, that bottlenose dolphins can mirror the behavior of conspecifics, the researchers said.

Many animals love to play extensively, especially during childhood. The movement sequences that are needed later – for example when hunting or fighting with other animals – are trained. Social interactions and hierarchies are learned and courtship and mating behavior can also be tried out in a playful way.

In some animal groups such as wolves, primates and dolphins, adult group members still often play. Communication is crucial: the behaviors and facial expressions used sometimes show patterns typical of aggression – friendly play can inadvertently turn into a real fight.

An example of such communication is the open mouth expression, which is probably derived from biting: a mouth that is wide open, but where the teeth are not shown threateningly and the overall facial expression remains relaxed. It sends a signal to the other person that all arguments and annoyance should be seen as fun. The researchers explain that the expression can also be seen in people: when they laugh.

A lifetime of fun
Bottlenose dolphins are also up for lifelong fun. They use natural waves to ‘surf’ or swim in the bow wave in front of ships, jumping several meters high out of the water and hitting the water surface with their tail fin. Tang, corals and other sea creatures are also popular play objects. The dolphins also specifically create air bubbles underwater with which they play. It is better to do all this together with others than alone.