Dogs and their humans have very special relationships. How strong these are can even be seen in the eyes of the four-legged friends. You cry with happiness. At least that is the result of a research team from Japan
Dogs can shed tears of joy when they see their master or mistress again. This is what a team led by the Japanese researcher Takefumi Kikusui from Azabu University in Japan writes in the journal Current Biology. The scientists investigated whether not only humans, but also their four-legged friends sometimes cry when they are emotionally overexcited. "We found that dogs shed tears associated with positive emotions," Kikusui said in a statement. Oxytocin, also known as the “cuddle hormone”, may play a decisive role in this.
Kikusui and colleagues made the discovery after one of his two poodles had puppies. When her puppies were being suckled, something changed on her dog's face: the scientist says she had tears in her eyes. "That gave me the idea that oxytocin might increase tears," says Kikusui.
The hormone produced in the brain plays a major role in childbirth as well as in coexistence among people. It induces labor, stimulates milk production, strengthens the bond between mother and child, and can also strengthen couple bonds and build trust in other people among adults.
From earlier observations, the researchers working with Kikusui also knew that oxytocin is released during interactions in both dogs and their owners. They now wanted to find out whether dogs cry when they are reunited with their master or mistress. That was exactly the case - unlike a person they didn't know. Also, when they added oxytocin to the dogs' eyes, their tears increased.
The results also surprised the research team: "We had never heard of animals shedding tears in joyful situations, such as reuniting with their owners, and we were all excited that this would be a world first!" Dogs, the researchers say, appear to produce tears in situations that humans see as "happy." The question remains open as to whether dogs also cry when faced with negative emotions.