True love: Dogs cry happy tears of joy when their owners come home

SAGAMIHARA, Japan — Dogs often bounce around uncontrollably when their favorite humans come home from work — but a new study reveals many also cry happy “tears of joy” just like people!

When Professor Takefumi Kikusui’s poodle had puppies six years ago, he noticed the dog’s face change when it nursed the puppies. His furry friend had tears in her eyes.

“That gave me the idea that oxytocin might increase tears,” Kikusui says in a media release.

The study author explains that dogs produce tears, they just don’t fall down their faces like a human's tears do. Prof. Kikusui, of Azabu University in Japan, followed up on his idea and discovered dogs had more tears in their eyes than normal when reunited with their owners. Moreover, their base level of tears didn’t change when they met someone they didn’t know.

When the researchers added oxytocin to the dogs’ eyes, they filled up with tears too, supporting the theory that the release of oxytocin causes dogs to cry when they’re back together with their owners. Previous studies have revealed that dogs release the hormone naturally when they play with their owners. However, studying this reaction when dogs reunite with their absent owners is new.

The Japanese team also asked people to rate pictures of dogs’ faces with and without artificial tears in them, and people loved the teary-eyed pets more. This suggests dogs’ tears help forge stronger connections between people and their dogs. The findings were particularly surprising to Prof. Kikusui.

“We had never heard of the discovery that animals shed tears in joyful situations, such as reuniting with their owners, and we were all excited that this would be a world first!” Prof. Kikusui explains.

“Dogs have become a partner of humans, and we can form bonds,” Kikusui concludes. “In this process, it is possible that the dogs that show teary eyes during interaction with the owner would be cared for by the owner more.”

The study, published in the journal Current Biology, showed dogs shed tears in happy situations, but they haven’t tested it on negative emotions yet.

The research team has yet to discover if dogs cry when they reconnect with other dog pals, but they hope to figure out if this tearful reaction also has a social function in the canine world.

South West News Service writer Pol Allingham contributed to this report.