WASHINGTON, Aug. 27 (Xinhua) -- Wolves, like humans, chimps and dogs, may also be susceptible to contagion of yawning, according to a study published in the U.S. journal PLOS ONE Wednesday.
Several studies have proposed that contagious yawn is linked to human capacity for empathy, but little evidence exists that links contagious yawning to empathy in animals outside primates. Only recently domestic dogs have demonstrated this ability when exposed to human yawns.
In the new study, researchers observed yawning in a single pack of 12 wolves at Tama Zoological Park in Tokyo, Japan, over five months, in situations without visible signs of stress.
The researchers recorded the exact time of the yawn, the identity of the initial yawner, and the identity and position of subjects close to the initial yawner.
"The wolf is an ideal model species to explore this phenomenon because it is the dog's closest phylogenetic relative and a highly social and cooperative species," they said in the paper. "If contagious yawning is shared by other social mammals, we would expect it to be present in the wolf."
The researchers found that yawning did occur "significantly more often" when wolves were exposed to another wolf's yawn.
"Wolves' susceptibility to yawn contagiously was affected by the strength of the social bond with the initial yawner, with wolves yawning more frequently to close social partners' yawns than to other individuals' yawns," said the study.
Additionally, female wolves showed a faster reaction time than males when observing yawns of close associates, suggesting that females are more responsive to surrounding social stimuli, it said.
Despite the small sample size, the researchers said these results may provide initial evidence that contagious yawning may relate to the wolves capacity for empathy.
The findings also suggested that basic building blocks of empathy might be present in a wider range of species than previously thought.
"In wolves, as well as in primates and dogs, yawning is contagious between individuals, especially those that are close associates," lead author Teresa Romero from the University of Tokyo said in a statement. "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."