The Big, Furry Carnivore That Catches Yawns From Friends
Like a case of chickenpox or an ice bucket challenge, a yawn can be pretty contagious. Humans have caught yawns by looking at each other, seeing pictures of people in the midst of yawning and even by thinking about yawning long enough. Research also points to chimpanzees, bonobos and dogs as other species who catch yawns. And a recent report in the journal PLOS One adds wolves to the list, too.
"In wolves, as well as in primates and dogs, yawning is contagious between individuals, especially those that are close associates," says Teresa Romero, a behavioral and cognitive scientist at the University of Tokyo, in a statement.
In a study of 12 gray wolves at Tama Zoological Park in Tokyo, Japan, Romero and her colleagues observed the animals' actions over a period of five months. (None of the wolves showed signs of stereotypic behavior that affect captive species, the authors write; the researchers did not address impacts captivity had on this research, however, beyond calling for future studies in wild populations.) An individual wolf was much more likely to yawn if he or she had spotted another wolf yawning, the scientists report.
Wolves with tighter social bonds more frequently caught each other's yawns, and female wolves were particularly sensitive. "Although our results should be taken with caution due to our small sample size," the authors write, "the observed sex difference in reaction time probably reflects the higher ability of female wolves to react to the emotional stimulus of their close associates."
Past studies have found associations between the likelihood that someone will yawn and a high self-reported sense of empathy. And Romero's earlier research indicates that dogs will more regularly catch their owners' yawns than the yawns of strangers. But before this study, the University of Tokyo researchers and their colleagues believed that this possible canine empathy might have stemmed from domestication.
The wolves' contagious yawns, however, indicate that this behavior existed in dogs before humans got involved. "These results suggest that contagious yawning is a common ancestral trait shared by other mammals, and that such ability reveals an emotional connection between individuals," Romero says.
Most of yawning's evolutionary roots remain a mystery, but there's one question that's been definitively put to rest: The cutest yawners on the planet? Puppies.