Dogs Produce Tears When Reunited With Owners, Study Finds

If your canine companion ain't nothing but a hound dog, crying all the time, it may be because they are brimming with emotion. From a report: Researchers in Japan say they have found that dogs produce tears when reuniting with their owners. What's more, the blubbing appears to be linked to levels of the "bonding hormone" oxytocin. "This is the first report demonstrating that positive emotion stimulates tear secretion in a non-human animal, and that oxytocin functions in tear secretion," the team said. Writing in the journal Current Biology, they describe how eye contact between humans and dogs encourages the former to care for the latter, while the gaze of a dog can cause a release of oxytocin in its owner. Dogs have also evolved the ability to raise their inner eyebrows, a trait that scientists say induces humans to nurture them. Now researchers in Japan have found tears might have a similar effect. "I have two standard poodles and I had one female pregnant six years ago," Prof Takefumi Kikusui, a co-author of the research at Azabu University, told the Guardian. Noticing her face was more tender than usual when nursing her puppies, Kikusui realised her eyes were teary. "That gave me the idea that oxytocin might increase tears," he said. "We previously observed that oxytocin is released both in dogs and owners when interacting. So we conducted a reunion experiment." In the first step, the team measured the volume of tears produced by 18 dogs when in their normal home environment with their owner, using Schirmer's test. This involves placing a special strip of paper inside the lower eyelid and measuring how far along the strip the moisture travels.

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