Watch a group of lions yawn, and it may seem like nothing more than big, lazy cats acting sleepy, but new research suggests that these yawns may be subtly communicating some important social cues. Yawning is not only contagious among lions, but it appears to help the predators synchronize their movements, researchers report March 16 in Animal Behaviour. 

The discovery was partially made by chance, says Elisabetta Palagi, an ethologist at the University of Pisa in Italy. While studying play behavior in spotted hyenas in South Africa, she and colleagues often had the opportunity to watch lions (Panthera leo) at the same time. And she quickly noticed that lions yawn quite frequently, concentrating these yawns in short time periods.

Yawning is ubiquitous among vertebrates, possibly boosting blood flow to the skull, cooling the brain and aiding alertness, especially when transitioning in and out of rest (SN: 9/8/15). Fish and reptiles will yawn, but more social vertebrates such as birds and mammals appear to have co-opted the behavior for purposes conducive to group living. In many species — like humans, monkeys, and even parakeets (SN: 6/1/15) — yawners can infect onlookers with their “yawn contagion,” leading onlookers to yawn shortly afterwards.

Seeing the lions yawn reminded Palagi of her own work on contagious yawning in primates. Curious if the lions’ prodigious yawning was socially linked, Palagi and her team started recording videos of the big cats, analyzing when they were yawning and any behaviors around those times. 

Over four months in 2019, the researchers closely monitored 19 lions at the Greater Makalali Private Game Reserve, just west of Kruger National Park. The team found that lions that saw another member of the pride yawn were about 139 times as likely to yawn themselves within the next three minutes. 

But the yawn contagion didn’t stop there. Lions that caught a yawn from another lion were 11 times as likely to mirror the movements of the original yawner than those that hadn’t. This “motor synchrony” involved one lion yawning, then another yawning, then the first getting up and walking around or laying back down and the other doing the same thing. 

In lions, contagious yawning might be important for maintaining social cohesion, Palagi says. Yawns that help lions harmonize their group movements could help get the pride all on the same page, crucial behavior for an animal that hunts and rears offspring cooperatively. 

“If yawn contagion has evolved to foster the creation of bonds,” says Palagi, “after a yawn contagion event, the two animals need to do something together [like getting up and walking] to increase their probability of interacting.”

Other researchers have hypothesized that yawning could help coordinate group behavior in some species, notes Andrew Gallup, a biopsychologist at State University of New York Polytechnic Institute in Utica. “But this is the first study that I’m aware of that’s actually attempted to quantify that,” he says.

“The spreading of [yawning] across the group via contagion could serve to enhance overall collective vigilance,” says Gallup. “I think as time continues, we’ll find that the contagious yawning is more common among some of these highly social species.”

Palagi notes that yawning often marks a shift between different physiological or emotional states. So, a yawn could be a good way for an individual in a social species to communicate to group mates that it is experiencing some kind of internal change. 

“Yawning is a widespread behavior, but I think it’s one of the most mysterious,” Palagi says, since it appears to have different functions from species to species.