Dog owners know the sheer joy of coming home from a long journey and being greeted by tail-wagging, uncontrollably jumping, and face-licking companions.
But these ecstatic dogs may have ripped off more than just the fur on their clothing, according to new research published Monday in the journal Current Biology.
“We hadn’t heard of any discovery that animals shed tears in joyful situations, such as reuniting with their owners,” said Takefumi Kikusui, one of the authors of the study, which may be a “world first.” said.
Scientists measured the amount of tears in the dog’s eyes with the widely used Schirmer test, which consists of placing a special strip under the eyelid. For baseline readings, they performed tests on dogs during normal interactions with their owners.
Researchers found that when dogs were separated from their owners for five to seven hours and then reunited, their tear production increased “significantly” in the next five minutes.
They also found that dogs shed more tears when reunited with their owners than other people they knew well.
Researchers say this tearing response is likely related to the release of oxytocin, called the “love hormone” because of its connection to bond building.
Scientists sought to test whether tears had an emotional effect on their owners. We asked them to rank them according to how much they would like to be taken care of.
“Photos of dogs with artificial tears ranked significantly higher than those without normal tears,” the Japanese research team wrote.
Kikusui hypothesized that “the more teary-eyed a dog is when interacting with its owner, the more likely it is that the owner will take care of it.”
In humans, infants share negative emotions through crying, which leads to more parental care, the authors note.
Unlike other animals, dogs domesticated by humans have developed certain communication skills over time. Eye contact has been shown to play a role in shaping the relationship between dogs and their owners.
In a future study, researchers hope to test whether dogs shed similar tears when meeting other canine companions.-AFP