Rapid tail flapping, air hopping and irrepressible licking: every dog owner regularly experiences this joyful encounter with their animal, long after separation.
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But in this list of highly explanatory behaviors, there is also a more discreet sign. In a study published Monday in the journal, researchers showed that dogs also cry when they are reunited with their owners current biology.
“We’ve never heard of animals shedding tears in happy situations such as being reunited with their owners,” study author Takefumi Kikusui of Azabu University said in a statement.
The scientists measured the amount of tears produced using a commonly used test, the Schirmer test (made up of a strip placed under the eyelid). They took as a point of comparison a basic level that was raised when the dog is in its usual environment in the presence of its owner.
After five to seven hours of separation, the amount of tears increased “significantly” within five minutes of the dog’s reunion with its owner.
The volume of tears was also higher when the dog was reunited with its master, rather than another person.
According to the researchers, the production of tears is linked to the presence of oxytocin, nicknamed the “love hormone.”
They also sought to understand the practical role this effusion could play. For this, owners were asked to rate pictures of their dogs to indicate how much they wanted him to be taken care of.
Pictures in which the animal was given artificial tears were rated “significantly,” according to the study.
“It is possible that dogs that show hazy eyes while interacting with their owner are prompting the latter to take more care of them,” said Takefumi Kikusui.
The study indicates that the crying of children makes parents pay more attention to them in humans.
Domesticated like no other animal, dogs have developed specific communication skills over time. Eye contact has been shown to play a role in forming the relationship between a dog and a handler.
The researchers would then like to study whether dogs also produce tears when they find other species of their own kind.
