Warning: You might yawn while reading this. Yawning is famously contagious; just talking or even thinking about yawning can prompt a yawn in response. Contagious yawning is thought to be linked to empathy and social bonds. But humans aren’t the only species to exhibit this behavior. Many mammals do, and recently scientists discovered that zebrafish can catch yawns, too.

Not surprisingly, wolves, known for their deep social connections, are contagious yawners. Dogs, on the other hand, have not been shown to catch a yawn from other dogs. But they do catch yawns from humans. A study published last month in Animal Cognition found that contagious yawning has been seen in dog/wolf mixtures, but it is far more common in wolves. And among wolves, the relationships and hierarchies made no difference. High ranking wolves caught yawns from lower ranking wolves just as easily as they did from other high ranking wolves.

While the study underscores the strong social bonds in wolf packs (better thought of as families, as Doug Smith, the wildlife biologist who headed the program to reintroduce wolves to Yellowstone, once told me), it also tells us a lot about dogs. The domestication of dogs seems to have caused “man’s best friend” to form social bonds with humans more readily than with others of their own species. This is not surprising; it’s clear that dogs have evolved to see humans as their families. Or maybe they think of themselves as human.

And in case you’re wondering, cats do not yawn when their humans yawn or when other cats yawn. They just yawn when they’re bored — or when they want to let us know how boring we are.

’til next time,

Avery

PS — You won’t believe how much I yawned while writing this!