Yawning is also contagious in solitary animals

For the first time, contagious yawning has been demonstrated in solitary animals. It was already known that yawning is contagious in humans and other social group animals. Until now, it was unclear whether yawning is also contagious for animals that live in solitude. Researchers from Utrecht University, together with colleagues from Leiden and Mexico, now demonstrated the phenomenon in orangutans. They published their findings 17 December in Scientific Reports.

Yawning is highly contagious in humans and in some other very social, group-living animals such as dogs, wolves, parakeets, chimpanzees and bonobos. Seeing or hearing others yawn is likely to trigger yawns in the observer, and this is especially true for family and friends. For the first time, contagious yawning has now also been found in a species that roams its territory mostly in solitude and is less frequently engaged in social interactions: the orangutan.

An international group of researchers from Utrecht University, Leiden University and the Benemérita Universidad Autónoma de Puebla in Mexico investigated contagious yawning in orangutans of primate park Apenheul in Apeldoorn. Lead by Jorg Massen (Utrecht University), the team observed orangutans while they were watching videos of other orangutans that either yawned or had a neutral expression. They discovered that orangutans, like humans, are prone to catching yawns from others.

"Contagious yawning is a phenomenon that has fascinated science for a long time, but interestingly enough, we still do not really know what its function is. By looking at our close relatives and at animal species that vary in their sociality, we try to get a better picture of this", says behavioural researcher Jorg Massen.

The researchers were not only interested in whether orangutans yawn contagiously, but also in whether this automatic behaviour is influenced by how familiar the individuals on the videos are to the orangutans who watched the videos. To study this, orangutans saw videos of group members, strangers, or a 3D orangutan avatar named Waldo (kindly donated to the team by graphics designer Paul Kolbrink from XYZ-Animation).

While the orangutans were found to yawn contagiously, they seemed particularly sensitive to videos of ‘real’ orangutans, regardless of whether they were of a group member or a stranger. Interestingly, the yawns of Waldo did not result in more yawns.

The findings of the study show that contagious yawning is not confined to very social animals. The results show that this contagiousness is probably something that all great apes exhibit. According to the research team, it is important to continue to investigate the contagiousness of yawning, especially in more solitary animals such as pandas, tortoises, cats, foxes, and even snakes and other reptiles. "Only by studying this peculiar behaviour in a wide variety of animals can we elucidate why contagious yawning exists and whether it has a specific function," says first author Evy van Berlo, from Leiden University.

“The funny thing is that we sometimes also yawned in response to seeing the orangutans yawn. Perhaps this contagiousness between species could also be an interesting next step in the study of contagious yawning”, say co-authors Alejandra Díaz-Loyo and Oscar Juárez-Mora from the Mexican Benemérita Universidad Autónoma de Puebla.