A dog's ability to play fetch and other activities with humans is a learned behavior that likely occurred over time after humans domesticated dogs from gray wolves 15,000 years ago. Researchers believe dogs only began to interpret cues from humans after domestication happened.
Modern dogs differ greatly from wolves not only physically and genetically, but behaviorally as well.
Researchers decided to test 13 wolf puppies born in three different litters. Their goal was to determine if wolf puppies exhibit the same behaviors as domesticated puppies, which would help them pinpoint the origin of the behaviors. Their study published Thursday in iScience
, a Cell Press journal.
Spontaneously, three of the 8-week-old wolf puppies were intrigued enough by a ball that was thrown to retrieve it to a person they didn't know. It was the last thing the researchers expected.
"When I saw the first wolf puppy retrieving the ball I literally got goose bumps," said Christina Hansen Wheat, study author at Stockholm University in Sweden. "It was so unexpected, and I immediately knew that this meant that if variation in human-directed play behavior exists in wolves, this behavior could have been a potential target for early selective pressures exerted during dog domestication."
Hansen Wheat studies the effects of domestication on behavior. She and her colleagues raised both wolf puppies and domesticated puppies from the time they were 10 days old.
Then, both types of puppies went through a series of tests. One of those included a stranger throwing a tennis ball while encouraging the puppy to fetch and return it. None of the puppies, wolf or domesticated puppy, had experienced "fetch" before this.
The first two litters of wolf puppies weren't interested in the ball, and the researchers didn't expect them to be. They included the test because it was used for domesticated puppies.
But the third litter of wolf puppies ran after the ball. Two wolf puppies each retrieved the ball twice. One ran after the ball and returned it to the person three times.
"It was very surprising that we had wolves actually retrieving the ball," Hansen Wheat said. "I did not expect that. I do not think any of us did. It was especially surprising that the wolves retrieved the ball for a person they had never met before."
Previous research has shown that domesticated and non-domesticated species will follow human gestures if a food reward is given, according to the study. But in those cases, the animals were previously trained to follow the cues or knew the person conducting the study.
The researchers acknowledge a limitation of their study is how small it is, but it causes them to reassess that interpreting human social cues came from domestication. Instead, it's possible that this behavior can be traced back before wolves were domesticated into dogs.
"Wolf puppies showing human-directed behavior could have had a selective advantage in early stages of dog domestication," Hansen Wheat said.