The reunion between a dog and its master is known to be a real moment of joy and excitement: tail wagging, licks, frenzied hugs... But this moment also has its share of sadness.
According to a study published this Monday in the journal
Current Biology
, dogs also produce tears when they find their master after a long separation.
“We had never heard of animals shedding tears in happy situations,” said study co-author Takefumi Kikusui.
For the researcher, this may be a “world first”.
More tears for his master than for anyone else
The scientists measured the amount of tears produced using a widely used test, the Schirmer test (a strip placed under the eyelid).
They took as a point of comparison a basic level raised when the dog was in its usual environment, in the presence of its master.
After five to seven hours of separation, the amount of tears increases "significantly" within 5 minutes of reuniting.
The volume of tears is also higher when the dog finds its owner rather than another person.
According to the researchers, this tear production is linked to the presence of oxytocin, nicknamed the “love hormone”.
Tears to get attention
The practical role of these effusions has also been investigated.
The scientists asked the owners to classify several photos of their dog, indicating for each how much it made them want to take care of their companion.
Photos where artificial tears were administered to the dog were ranked "significantly" higher, according to the study.
“It is possible that dogs who have misty eyes during their interactions with their owner lead the latter to take care of them more”, advances Takefumi Kikusui.
In humans, babies crying cause parents to pay more attention to them, the study points out.
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