Contagious yawning observed in fish species

In a groundbreaking study published in Communications Biology on April 7, researchers led by Elisabetta Palagi, a comparative ethologist at the University of Pisa in Italy, have demonstrated contagious yawning in zebrafish, a cold-blooded species.

The species of fish used in the study was the zebrafish (Danio rerio). Palagi and her team trained an AI model to recognise the traits linked to yawning in zebrafish. The model was able to distinguish between a yawn and normal breathing in zebrafish, with zebrafish opening their mouths wider during a yawn than when simply breathing.

To study the responses of zebrafish, the team showed them videos of other zebrafish yawning and breathing normally. About half the time, a yawning zebrafish also stretched its body. This is the first time contagious yawning has been demonstrated in a cold-blooded species.

Noam Miller, a comparative psychologist at Wilfrid Laurier University in Waterloo, Ontario, Canada, finds the study "very interesting" and "surprising", but notes that there are many aspects still to be explored regarding fish yawning. Miller suggests there is a need to understand whether fish would yawn and do it contagiously for the same reasons as warm-blooded animals.

Cait Newport, a biologist who studies fish behavior at Oxford University in England, finds the observations an intriguing "good start" but believes more clarity is needed on why fish would yawn together. Palagi states that this study opens up opportunities for numerous future studies on yawning and contagious yawning in zebrafish.

The reason animals yawn is still an open question, according to Palagi. However, the directional change in response to yawning observed in zebrafish in the lab might be a potential method for coordinating movements in the wild.

If you have further questions or need more information, please do not hesitate to ask.