We all love coming home to our beloved pups after a long break, and for the most part our dogs love it too.
But new research has suggested that dogs may even shed a tear of joy when they are reunited with their owner. Well, maybe not 'shed' as a dog's tears do not fall like they do in humans - but a new study has found that there may still be 'happy tears' in their eyes.
The research was carried out by Azabu University in Japan, after a researcher noticed that his dog appeared to tear up when nursing her pups. Noticing the tears, the researcher wanted to find out what would trigger them and whether happiness could cause dogs to cry.
The study looked at whether adding the hormone oxytocin to a dog's eyes made it tear up, which it did. This supports the idea that a natural oxytocin release which can occur when a dog is reunited with its owner could cause tears of joy, reports the Mirror.
Professor Takefumi Kikusui also found that a pup's base level of tears didn't change when they met someone they didn't know. This may suggest that it is the joy of a familiar face that makes them well up.
It was already known that oxytocin is released in dogs and their owners when they play, but studying the reunification of the two 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.
Prof Kikusui, who was surprised by the results, explained: "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!"
He added: "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 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 are 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.
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