Few animals show as much affection and loyalty as dogs. But a new study offers evidence that the same human-to-animal attachment can develop in wolves, too.
While earlier studies have suggested something similar, there isn't much previous research on the attachment between wolves and humans, and the results have varied. Here, the study team wanted to take a standardized approach in which a test group of dogs and wolves were raised in identical circumstances from birth.
Between 40,000 and 15,000 years ago, dogs were domesticated from wolf species that are now extinct, and the researchers think that their findings could shed new light on which traits have evolved through domestication, and which were there in the first place.
"Wolves showing human-directed attachment could have had a selective advantage in early stages of dog domestication," says ethologist and the study's lead author Christina Hansen Wheat from Stockholm University in Sweden.
The study looked at the responses and behaviors of 12 Alaskan husky dogs and 10 European gray wolves (Canis lupus) in what's known as the Strange Situation Test, a standard scientific test originally used with children to judge attachment towards their caregivers, and was adapted for dogs (and in this case, wolves) 20 years ago.
Having been raised from the age of 10 days up to 23 weeks by trained caregivers, the dogs and wolves were put through a roughly 15-minute long experiment.
In it, the primary female caregiver to the wolves and dogs would take turns with a female stranger going in and out of a room and engaging with the animals, whether through active play or, if the animal engaged them, petting.
Like the dogs, the wolves showed more affection and spent more time greeting the familiar person, and engaged in more physical contact. The familiar person was also more likely to be followed to the door as they left.
"It was very clear that the wolves, as the dogs, preferred the familiar person over the stranger," says Hansen Wheat.
"But what was perhaps even more interesting was that while the dogs were not particularly affected by the test situation, the wolves were."
Compared to the dogs, wolves demonstrated more stress- and fear-related behaviors when dealing with strangers, including pacing, crouching, and tail-tucking.
These behaviors coincided with the stranger entering the room and when the stranger and the wolf were in the room without the familiar person.
When the familiar human returned to the room, these behaviors would become less pronounced. In other words, it seemed as though the familiar person acted as a sort of 'social buffer' for the wolf.
Scientists continue to examine the ways in which dogs and wolves are and aren't alike, in an attempt to understand their evolutionary history – but it appears that in terms of bonding with people, there are some key similarities. The differences, however, suggest areas that be further explored in future research.
"Together with earlier studies making important contributions to this question, I think it is now appropriate to entertain the idea that if variation in human-directed attachment behavior exists in wolves, this behavior could have been a potential target for early selective pressures exerted during dog domestication," says Hansen Wheat.
The research has been published in Ecology and Evolution.