The title question might seem a little silly - they like to play because it's fun! But dogs are one of the only species where playful behaviour persists into adulthood, and they are also one of the most playful species of all. In fact, according to scientists at the University of Bristol in England, both domestic dogs and cats like to play much more than their wild ancestors are thought to have done.
However, while cats almost exclusively play in a way that mimics the hunting of small prey, dogs prefer to play with a partner - whether another dog or a human - and it's thought to be mostly for social reasons. The primary purpose is generally agreed upon to be to help young dogs learn social skills - you might notice this when puppies play together, and one yelps - and playtime suddenly stops.
Two authors have even claimed that dogs appear to follow rules during play time with other dogs, largely signaled by play bowing - a pose you've almost certainly seen, but maybe don't know the name of (see the image below).
Those rules are claimed to be:
- Ask first.
- Be honest.
- Follow the rules.
- Admit when you're wrong.
Imagine a common scenario between two dogs - Rex and Odin. Rex might decide he wants to play with Odin, and will approach Odin and play bow. If Odin wants to play too, he'll engage with Rex. After a while, maybe Rex gets a bit too excited and bites Odin just a little too hard. Odin yelps, which signals that play time is over. Rex didn't mean to cause an injury though, so he pins his ears back and play bows again - as if to say "I didn't mean to, I am just playing".
It might seem crazy to think that dogs could come up with rules like this - but research suggests that dogs are great at learning which behaviours will lead to longer play time, so that both play partners can better enjoy the benefits of play time (such as exercise, social bonding, and stress relief). This kind of behaviour has even been observed in Wolves, Coyotes and even Wild African Dogs.
Of course, you've probably thought to yourself already that not all play is social. Chances are that your dog (or dogs) probably likes to sometimes amuse themself by playing with a toy on their own. Mine often goes crazy late at night, running around the house growling while squeaking a toy in his mouth at the same time! In the case of solitary play time, dogs do appear to also enjoy playing in a way that mimics the hunting activities of their ancestors.
As for play fighting and playing rough, researchers found that while dogs are willing to play rough with unfamiliar dogs - play time lasts much longer if the dogs are familiar with one another. In fact, in established friendships between dogs, two dogs may even have their own sets of rules that they play by. For example, in some dog friendships, there may be a significantly stronger dog that "self handicaps" and allows the other dog to win. Conversely, in some friendships - the stronger dog may insist on "winning" every bout of play time.
Maybe unintuitively, a one-sided outcome to every bout of playing doesn't usually seem to matter to the underdog (heh). The theory for this is that dogs don't care so much about winning or losing during play time, but instead simply enjoy interacting with their friends, even if they "lose" every game.
Dogs have even been shown to learn the play strategies (and social reputations!) of other dogs just by observing them playing with humans or other dogs. A dog that has been spectating is more likely to approach the winner of the observed game (whether a human or a dog). Interestingly, even when the dog cannot see the game being played (but is nearby and can hear or smell it), they can still tell who the winner is. Scientists believe this might be due to vocalisations from other dogs that indicate whether they are winning or losing, as well as social cues being given off by victors and losers.
In short - dogs like to play partly because it's leftover behaviour from their wolf ancestors, partly because it's one of the ways that they bond with friends (both human and canine), and it's also good for their health.
For more info, check out the video below! And if you want to get some new stuff to include in games between you and your dog, go check out our range and use code PAWFECT20 at checkout for 20% off!
 Wild Justice: The Moral Lives of Animals, by Dr. Marc Bekoff and Jessica Pierce