If you hear two people laugh, chances are you’re going to smile or laugh yourself because laughter is contagious — and not just for humans. Some birds get giggle fits, too.
Wild keas — a large parrot species from New Zealand — engaged in playful behavior when researchers played recordings of kea play calls on speakers. Many birds began playing with their more serious compatriots, while others began playing with objects, or started performing aerobatics in the air, according to a study published today in Current Biology. Other studies found that chimps and rats may find laughter contagious. This study adds birds — which are distantly related to humans — to the list.
To test the parrots’ taste for fun, the researchers played recordings of chirps made by keas when they’re playing. For control, they also played two other types of non-play kea calls, a tweet from a local robin, and a bland tone. When the keas heard the “laughter” chirps, they went into play mode, much more than when they heard the other sounds.
"The fact that at least some of these birds started playing spontaneously when no other birds had been playing suggests that, similar to human laughter, it had an emotional effect on the birds that heard it, putting them in a playful state,” study co-author Raoul Schwing of the Messerli Research Institute in Austria said in a statement.
The study might not show that the playful warbling actually had an emotional effect on the birds, Elodie Mandel-Briefer from ETH Zurich tells The Atlantic. Sometimes, alarm calls trigger alarm in animals, and aggressive calls trigger aggression. But to show whether actual emotions are triggered in keas by the “laughter” you would have to “find some way of measuring the emotional state of both the callers and listeners.”
Still, the study adds to our understanding of keas, which are known for being very playful. Unfortunately, they’re threatened because of possums and stoats that eat their eggs, lead poisoning, habitat loss, and illegal trade.