Are my dogs playing or fighting?

Start with the body. The AKC's guide to rough play describes playing dogs with big, silly, open-mouthed grins, front ends dropped into play bows, and dogs that flop down on purpose to make themselves vulnerable. They take turns, and they keep circling back for more. None of that has to be quiet or gentle. Playing dogs can be loud and fast and still be playing, as long as both of them keep choosing the game.

A fight changes the picture. The same AKC guide lists raised hackles along the upper back, low warning growls, closed mouths and curled lips, ears pinned flat and tails tucked. The biggest difference is what the losing dog does: in play it comes back, and in a conflict it tries to get away and does not return. If one dog is always pinned, always chased and keeps looking for an exit, the game has stopped being a game for that dog.

A real fight is a different job. The AKC's advice on breaking up a dog fight starts with what not to do: do not jump in, and keep your hands away from the dogs' mouths, because even your own dog will not tell friend from foe in that moment. Do not grab a collar or use any part of your body to push between them. Instead, interrupt with something big, such as a loud noise from banging metal objects together, or water from a hose.

If noise does not work, put a barrier between them: a sheet of plywood, a baby gate, a trash can lid or a large push broom, keeping your face well back. The AKC describes a last-resort method for two people, each lifting one dog by the hind legs from behind and walking backward until the dogs are apart. Once they are separated, keep them in different rooms until both have calmed down completely, and skip any reunion play that day.

VCA's veterinary behaviorists describe the usual flashpoints between dogs who live together: access to something valuable, such as a favorite bone, a toy, a resting spot, a food bowl or a special person, and tight moments like squeezing through a narrow doorway or rough play that runs too long. They note that trouble often begins when the younger dog matures socially, somewhere between one and three years of age, and that both dogs should be examined by a vet, because pain can make a dog snap when approached.

At home, feed and give chews apart, give each dog a place to retreat, and end games while both dogs are still loose. Off-season beaches bring the most unplanned meetings on Cape Ann; Good Harbor takes dogs on even-numbered days from October 1, and not every loose dog there is a good playmate. At Dogtown every dog starts with a free evaluation, and groups of 7 to 10 are matched by size, play style and temperament. Training sessions start from $94, including Calm & Connected for impulse control.