Dogs “cry happy tears” when owners return home, a new study has found.
The study, published in the journal Current Biology, found that dogs shed tears in happy situations, but the researchers haven’t tested what happens when the dogs are faced with negative emotions.
Lead author Professor Takefumi Kikusui was inspired to conduct the study when his poodle had puppies six years and he noticed the poodle had tears in her eyes after giving birth.
“That gave me the idea that oxytocin might increase tears,” Kikusui explained, adding that while dogs’ eyes produce tears, they don’t fall in the same ways as humans.
The researcher from Azabu University in Japan also discovered that dogs had more tears in their eyes when reunited with their owners.
He found that the base level of tears in a dog’s eye doesn’t change when the dog meets someone new, so the increase in “tears” is a reaction to seeing someone the dog knows.
During the study the researchers also added oxytocin to the dogs’ eyes which caused them to fill up with tears, supporting the theory that higher levels of oxytocin – often known as the “love hormone” – are present when a dog sees its owner.
Previous studies had found that oxytocin was released when dogs and their owners play, but this is the first study to unify oxytocin and tears in dogs.
“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,” Kikusui said.
“Dogs have become a partner of humans, and we can form bonds. 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 research team are now looking into whether dogs “cry” when they are reunited with their canine pals.
Additional reporting by SWNS.
