Verified by 
I like to go to dog parks to watch the dogs and the people. For a book I'm writing on dog behavior, for convenience, I lay out the different types of interactions as dog → dog, dog → human, human → dog, and human → human. Numerous questions always arise about what the dogs and humans are doing and I love to hear how their humans are interpreting their behavior (please see "Butts and Noses: Secrets and Lessons from Dog Parks"). And, what's really exciting is that the list of questions continually grows. Sometimes I feel overwhelmed with the questions that arise, but it's just great that people are genuinely interested in learning more about what their canine friends are doing, thinking, and feeling. And, there still is much to learn.
What's happening when dogs play tug-of-war? Some preliminary data
On a good number of occasions I've watched dogs play tug-of-war and have listened to different explanations for what's happening. Often there's agreement and sometimes there are disagreements that range from mild to hot. People can get get pretty fiery and I usually stay clear of the discussions unless the humans know what I do for a living and ask for my opinion. And then still, I'm very cautious about saying this is what's surely happening because it seems like the minute we say we know it all, something happens that contradicts our certainty. This is why studying dogs is so very exciting.
One discussion I remember well occurred when a woman said something like, "When dogs play tug-of-war they're competing with one another." She said it with alarming certainty and told me and other people she'd read it somewhere but couldn't remember where. I politely mentioned that it's surely more complex and interesting than that, and kind of forgot about the discussion.
Because I'm voraciously reading to see what others think about all sorts of dog behavior, just yesterday I came across the statement to which the woman was likely referring. In Dr. John Bradshaw's book called Dog Sense: How the New Science of Dog Behavior Can Make You A Better Friend to Your Pet he writes, "Dogs playing with a tug-toy are actually competing." (p. 205) He correctly notes that there are differences when dogs play tug-of-war with a person or with another dog. Along these lines, Dr. Bradshaw writes, "In short, dogs appear to be in a completely different frame of mind depending on whether they are playing with a person or with another dog. When the play-partner is a dog, possession seems to be most important – and indeed, it's possible that competitive play is one way that dogs assess each others' strength and character. ... dogs put humans in a completely different mental category from other dogs." (my emphasis)
Surely, this is but one possible explanation of what's happening when dogs play tug-of-war with one another. However, it's actually more complex and interesting than being just competition. I've watched numerous tugs-of-war among dogs and wild coyotes. The picture here is of Molly (left) playing tug-of-war with her friend Charlotta. They'd run frantically about, each holding tightly onto the rope. Then, one would let go and tease the other, they'd then run around each holding the rope in her mouth, and the game went on and on. There was no obvious competition at all and they'd freely exchange possession of the rope for minutes on end. They were friends and clearly they enjoyed what they were doing.
So, are dogs "actually competing" when they play tug-of-war? On some occasions they might be. I looked at 50 random tugs-of-war out of the many I'd observed during different visits to dog parks, and while these are only preliminary data, they show clearly that competition is but one explanation, but surely not the only one for what's happening when dogs play tug-of-war. I always had another person observing with me to be sure both of us were on the same page about what was happening. Most of the people really enjoyed doing this because it was part of an informal course on dog ethology and they were eager to learn more about their dog. On four occasions we disagreed.
So, how did we go about performing this pilot study? First, there are a number of variables that need to be considered, including the relative size of the dogs, their social relationship and familiarity with one another, gender, context -- what they were doing right before they began playing tug-of-war -- age, and perhaps breed. We had information on all of these variables.
In a nutshell, when dogs of different sizes played tug-of-war we observed what ethologists call self-handicapping – if the game was to continue the larger dog had to restrain how hard she/he pulled on the rope. When a large dog pulled so hard so that the smaller dog couldn't play, the game usually ended. On one occasion, a large mutt pulled so hard he almost lifted his small friend off the ground. When he saw what was happening, he dropped the rope, ran right at her, skidded to a stop, and did a play bow. He wanted to play – and they did – and clearly tug-of-war wasn't going to work. Self-handicapping is also observed in other forms of play (please see "Dogs at Play: What They Do, Know, Think, and Feel" and links therein).
Familiarity also was important – when dogs such as Molly and Charlotta played tug-of-war there were more exchanges and a willingness to let the other dog have the rope. We didn't see any interactions that indicated competition. It was more difficult to assess how what was happening previously – were the dogs playing, just walking about, wired from other encounters with other dogs – influenced the outcome of tugs-of-war. However, once again, the impression we got was that if a rope was picked up during an on-going play interaction or right after one of the dogs had been playing, the play continued as the dogs yanked on the rope and exchanged it on the run. On seven occasions we agreed that there was a competitive element and four times there were some growls and a clear indication that one dog wanted the rope all for her/himself. We only saw one instance where there was a strong likelihood that if one of the dogs didn't give up the rope there would have been a fight. We didn't observe any gender differences or breed differences, and many of the dogs were mixes.
There's a lot of research that needs to be done: The importance of dog park chatter, data, and science
So, my conclusion is that when dogs play tug-of-war it's more complex and interesting than to saying they're "actually competing." Sometimes they may be, but most of the time the dogs we observed were not. Clearly we need a lot more research in this area and dog park chatter and data – citizen science –can help us along. And, what's so very exciting is that there are many theses just waiting to be done in this area and many others. There still is so much to learn about dogs and their humans.
For more on dogs please see "On Comparisons Between Dogs and Wolves: What We Really Know" and "Hugging a Dog Is Just Fine When Done With Great Care."
Marc Bekoff's latest books are Jasper's Story: Saving Moon Bears (with Jill Robinson), Ignoring Nature No More: The Case for Compassionate Conservation, Why Dogs Hump and Bees Get Depressed: The Fascinating Science of Animal Intelligence, Emotions, Friendship, and Conservation, Rewilding Our Hearts: Building Pathways of Compassion and Coexistence, and The Jane Effect: Celebrating Jane Goodall (edited with Dale Peterson). (Homepage: marcbekoff.com; @MarcBekoff)
