He watches as a group of lions yawn and may look like nothing more than big, lazy cats acting asleep, but new research suggests these yawns may be subtly communicating some important social clues. Yawns are not only contagious among lions, but appear to help predators synchronize their movements, researchers reported on March 16 in Animal Behavior.
The discovery was made partly by chance, says Elisabetta Palagi, an ethologist at the University of Pisa in Italy. While studying the behavior of the game in spotted hyenas in South Africa, she and her colleagues often had the opportunity to see lions (Panthera leo) at the same time. And he soon noticed that the lions yawned quite frequently, concentrating these yawns in short periods of time.
Yawning is ubiquitous among vertebrates, possibly increasing blood flow to the skull, cooling the brain, and aiding vigilance, especially when traveling in and out of rest (SN: 9/8/15). Fish and reptiles will yawn, but more social vertebrates such as birds and mammals seem to have opted for behavior conducive to group life. In many species, such as humans, monkeys, and even parakeets (SN: 01/06/15), yawners can infect viewers with their “yawning contagion,” which leads onlookers to yawn soon after.
Watching the lions yawn reminded Palagi of his own work on contagious yawning in primates. Curious if the prodigy yawn of the lions was socially related, Palagi and his team began recording videos of the big cats, analyzing when they yawned and any behavior of those times.
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For four months in 2019, researchers closely monitored 19 lions in the Greater Makalali Private Game Reserve, west of Kruger National Park. The team found that lions who saw another member of pride yawn were about 139 times more likely to yawn in the next three minutes.
But the yawning contagion didn’t stop there. Lions that caught a yawn from another lion were 11 times more likely to reflect the movements of the original yawn than those that did not. This “motor synchrony” implied that one lion yawned, then another yawned, then the first stood up and walked or leaned back and the other did the same.
In lions, contagious yawning can be important in maintaining social cohesion, Palagi says. The yawns that help lions harmonize their group movements could help make pride on the same page, a crucial behavior for an animal that hunts and raises offspring cooperatively.
"If yawning contagion has evolved to encourage bonding," says Palagi, "after a yawning contagion event, the two animals need to do something together (like get up and walk) to increase their likelihood of interacting."
Other researchers have hypothesized that yawning could help coordinate the group's behavior in some species, says Andrew Gallup, a biopsychologist at the Polytechnic Institute at New York State University in Utica. “But this is the first study I’m aware of and I’ve really tried to quantify that,” he says.
“Propagation (yawning) by the group through contagion could serve to improve overall collective surveillance,” Gallup says. "I think as time goes on, we'll find that contagious yawning is more common among some of these highly social species."
Palagi points out that yawning often marks a shift between different physiological or emotional states. Thus, a yawn could be a good way for an individual of a social species to communicate to group mates who is experiencing some kind of internal change.
“Yawning is a widespread behavior, but I think it’s one of the most mysterious,” Palagi says, as it appears to have different functions from species to species.