The adorable reason dogs cry when you come back home

There's no denying it, pets are pretty adorable. Some of us are so enamoured with our furry friends that there are even people out there spending serious cash to look just like them, as is the case with a man who handed over 15,000 dollars for a super-realistic dog suit.

However, we still don’t know so much about the animal kingdom: we’re learning new things all the time about their emotional range and how they navigate the world. Back in February, for example, a study suggested that dogs grieve when fellow canine companions (like a sibling, parent or a dog they live with) pass away. More dog science dropped on Monday (22 August) when a new paper published in Current Biology made an intriguing discovery.

“We found that dogs shed tears associated with positive emotions,” Takefumi Kikusui of Azabu University in Japan, who worked on the study, says in a press release. “We also made the discovery of oxytocin as a possible mechanism underlying it.”

Kikusui and the other researchers working on the study were able to come to this conclusion by measuring the tear volume in dogs’ eyes before and after reunions with owners and familiar non-owners. They then found that dogs’ tear volume increased after a reunion with their owner but not a non-owner.

According to the team, an increase in oxytocin could be the reason for these sorts of teary dog-owner reunions. They were able to put this hypothesis to the test by applying oxytocin to dogs’ eyes — which was shown to lead to an increase in tear volume, too. To further investigate this phenomenon, the team then asked humans to rate their responses to dogs with tears in their eyes and dogs without — with crying dogs rated more positively.

As a result, the scientists are arguing that when dogs cry in this way, it leads to a stronger bond between them and their human. “Dogs have become a partner of humans, and we can form bonds,” Kikusui says. “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.”

Kikusui became interested in exploring the question of dogs’ tears due to having pooches of his own. Six years ago, one of the scientist’s two poodles gave birth to a litter of puppies — and he noticed something. When nursing her children, the doggie started tearing up slightly, suggesting that dogs cry tears in connection with specific emotions.

To the research team’s knowledge, there has previously not been research into the reasons why dogs may shed tears, with it widely being assumed that whether or not dogs well up is not linked to how they feel. “We had never heard of the discovery that animals shed tears in joyful situations, such as reuniting with their owners,” explains Kikusui. “We were all excited that this would be a world first!