Why do animals play? The answer seems like it should be obvious, but the more you think about it, the less you know. Is it for ‘practice?’ That makes sense, since play is seen mostly in young animals who are physically developing. However, some of the research suggests that practice is not the primary force driving play… (in some studies animals kept from playing are equally adept at predation and fighting.) Another idea proposed historically was that animals played if they had “excess energy.” It’s certainly true that play is only found in individuals who are healthy and safe enough to have the luxury of playing, but there is no data that suggests that ‘excess energy’ somehow needs to be used up!

One current hypothesis is that play allows animals to train their bodies for the ‘unexpected.’ Play usually includes many actions that involve quick responses and exaggerations of movements seen in other contexts, etc, so this hypothesis has some favor now. Perhaps there are several reasons that animals play… surely there doesn’t have to be only one reason.

But there DOES have to be a reason that play is so common in some species (“it’s fun” isn’t enough! why is it fun?). Play is costly and dangerous.

Another condundrum that scientists face when studying play is defining it in a way that uniquely defines a behavior as play. This is a tricky one, because most of the actions of play are seen in other contexts, like fighting and predation, for example. Certainly there are times that it is overwhelmingly clear that animals, our dogs for example, are playing. However, sometimes it’s not so clear.

Here’s a question for you about the photos below. Are these animals playing or fighting?