The kea parrot in New Zealand has been dubbed "the world's smartest bird" because of its playful, curious nature and ability to foil humans. It can learn how to open beer bottles and tear apart cars.

The clever bird even emits a laughter-like call when having a good time — and new research has found that the call has the effect of putting other listening kea parrots in a playful mood.

Calls with such a powerful influence on others are known as "emotionally contagious." It was previously determined that, in addition to humans, chimpanzees and rats produce emotionally contagious playful vocalizations, but the kea is the first known non-mammal to do so. The findings are published in the journal Current Biology.

"The warble or play call is akin to human laughter in the sense that it has a similar effect on the emotional state of the receiver," Raoul Schwing, lead author of the paper, told Seeker. "Both put the receiver in a more positive emotional state."

Schwing, a researcher at the Messerli Research Institute in Austria, noted that the bird's behavior is perhaps most similar to children who giggle while playing.

Photo: Juvenile kea parrot. Credit: Raoul Schwing

"Laughter in adults is more often associated with humor," he remarked in reference to humans. "Nonetheless, it still has an emotional contagion effect, as can be seen by the inclusion of the laugh track in situation comedies."

Schwing became interested in the kea play call after analyzing recordings of the parrot's full vocal repertoire, which is impressive. He then wondered how kea in the wild would respond if they heard the recorded play calls.

To find out, he and his colleagues played the calls to groups of wild kea for a period of five minutes. They also played other kea-made sounds, as well as calls from a South Island robin, as controls.

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When the birds heard the play calls, they started playing with other kea. If alone, they would play with a nearby object or perform aerial acrobatics. Apparently enjoying themselves, the playful birds would then often emit the same call.

The below video, shot by Raoul Schwing, shows a perched adult male and female kea listening to a recording of another bird's play call. Upon hearing it, they engage in a tussle-chase bout of play.

Since the birds in the study did not join in play that was already underway, the researchers do not think the call is an instruction to become frisky. Instead, they concluded that it induces playfulness due to its acting as a positive emotional contagion. This, in turn, could promote tolerance and sync up moods when an individual is interacting with others.

Since many other birds and animals play, it is possible that other species produce emotionally contagious laugh-like calls too. Some of the sounds may even be out of a range that humans can hear. Rats, for example, produce laugh-like vocalizations in ultrasound.

Laughter can come with a price, however. Playful animals are usually inattentive, so emitting sounds would draw even more attention to them at a time when they are already vulnerable to predators. Kea are vulnerable to extinction due to habitat loss and other human-related problems, but these birds actually have few other predators. This could help to explain why they evolved their own form of laughter.

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Emotionally contagious sounds are not always happy ones, though.

"Negative emotional contagions have been found in many more cases than positive ones," Schwing explained. "Alarm calls and aggressive growls, for example seem to have an emotionally contagious effect on the receiver."

Even sadness can be contagious, at least in humans. He noted that people might tear up watching others cry, or while listening to sad music at a movie. The shared misery perhaps helps us to empathize and therefore bond more with others, helping to explain the evolutionary benefit.

The scientists hope to determine more specifically how play and related calls help social animals, be they parrots or humans.

"If the theory holds true that they increase tolerance in groups," Schwing said, "then one could argue that humans could learn from this by adopting play and/or laughter as a form of social facilitation."

Top Photo: Two juvenile kea tussle playing on the ground. Credit: Raoul Schwing