The raising of hackles does not always mean aggressive tendencies. That is what we have always been taught, but in the real dog training/behavior world, hackles raised does not always means aggression. Just like a wagging tail doesn’t mean that the dog is happy/friendly. A wagging tail can mean so many different things, based upon how high the tail is when wagging, is it the whole tail, is it at the base, is it at the tip, etc. etc. As you can see, it can be VERY confusing trying to read the body language of dogs, but it is oh so important to learn!
The raising of hackles is just like goosebumps in humans. Dogs cannot control the raising of hair on his back, just like we cannot control when goosebumps show on our skin. Just think of when you get goosebumps. You get them when fearful, excited, sad….all different emotions. If we cannot control them, neither can a dog. A dog does not have the capabilities to raise his hackles to communicate what he wants to say. I have seen a dog’s hackles raise at the sight of a bag blowing across a parking lot, and another at the sight of a favorite toy. Some dogs tend to display hackles more often than not.
In your situation, if that is really the only time that you see Butch’s hackles raise, then I wouldn’t worry about it. It is still best that you keep an eye on the dogs when they are playing! They are like little kids when the play; one can get grumpy at the drop of a hat and then the fur will really fly! They should always be monitored when playing. If you feel that play may be getting out of hand, re-direct the dogs to something else to allow them some cool-down time. Dogs need breaks when they play together just to re-group.
I do not think that you have anything to worry about. Just watch playtime, the roughness, etc. Always be ready to step in and give the dogs a break if things look a bit too tough. That will help keep potential fights to a minimum. Keep in mind, Butch is only 6 months old. He needs to be taught proper play behavior, BEFORE he gets older. If he isn’t taught proper play, once he is older, he could really cause some trouble. Take him to puppy classes to see how he reacts there and if his play is “proper” for a dog his age. Classes are always the best way to learn if what he is doing is right or not. That is why there are trainers for all ages of dogs. This is a critical period in Butch’s life and you need to make sure you and Butch are on track to him being as successful as he can!