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Dogs Cry Tears of Happiness

Humans and dogs have been enjoying a symbiotic relationship of nurturing and trust for millennia. Dogs make people feel safer and loved and humans nurture their canine companions, providing them with a warm place to sleep, affection and treats. The result is a significant and lasting bond.

Dog reunited with its owner

With all the love that connects humans and pooches, scientists wondered if the canine half of the equation teared up more when they experienced a flood of emotion like humans do.

According to new research, the answer is yes, the eyes of pups do flood with tears on a regular basis when they get emotional, like when they’re reunited with their humans, reported

“We found that dogs shed tears associated with positive emotions,” said Takefumi Kikusui, a professor at the Laboratory of Human-Animal Interaction and Reciprocity at Azabu University in Japan, who is co-author of the research. “We also made the discovery of oxytocin as a possible mechanism underlying it.”

The results of the study, “Increase of tear volume in dogs after reunion with owners is mediated by oxytocin,” were published in the journal Current Biology.

A few years ago, Kikusui noticed that when his poodle was nursing her puppies there were tears in her eyes. That made Kikusui think that the “love hormone” oxytocin might cause an increase in tear production.

The research team already knew that dogs and humans release oxytocin when they interact. They measured the volume of tears the dogs had before and after they reunited with their humans and found that when they reconnected with them their tear volume increased. However, when the pups connected with someone they weren’t familiar with, they did not produce more tears.

“Dogs have become a partner of humans, and we can form bonds,” said Kikusui. “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 hasn’t yet looked into whether dogs produce tears when they’re unhappy. They also don’t know if they do so when they’re reunited with their canine friends, but hope to find out.


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