Dogs show jealousy when their owners spend time with what appears to be another dog, suggesting that the emotion may have survivalist roots, US researchers said Wednesday.
Scientists tested 36 dogs and their owners with an experiment in which the owners were told to play with three separate objects in front of their dog.
One of the objects was a toy dog that barked and wagged its tail when a button on it was pushed. The owners were told to play with it as if it were a real dog for one minute.
They were told to do the same in the next phase of the experiment with a toy jack-o-lantern pail, acting as if it were a dog and playing with it.
Finally, they were asked to read aloud a pop-up children's book that played a song, as if they were telling the story to a small child.
Certain dog behaviors were much more common when owners played with the toy dog versus the other objects, the researchers found.
For instance, dogs more often snapped, pushed their owners, pushed against the object and tried to get in between the owner and the toy dog than they did with the other toys.
The dogs were about twice as likely to push their owner (78 percent of dogs did this) when he or she was playing with the toy dog than when the interaction involved the jack-o-lantern (42 percent). Just 22 percent did so with the book.
About 30 percent of the dogs tried to get between their owner and the toy dog, and 25 percent snapped at the stuffed canine.
The dogs came from a range of breeds, including dachshund, Pomeranian, Boston terrier, Maltese and pug. Almost half of those in the study were mixed breeds.
The research, led by Christine Harris and Caroline Prouvost from the University of California, San Diego, is published in the journal PLOS ONE.
"Our study suggests not only that dogs do engage in what appear to be jealous behaviors but also that they were seeking to break up the connection between the owner and a seeming rival," Harris said.
"We can't really speak to the dogs' subjective experiences, of course, but it looks as though they were motivated to protect an important social relationship."
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