I'm petsitting for a neighbor right how. She has a 6 month old puppy who's a chihuahua/somthing with a flat face mix. I've got to watch a lot of play behavior and how I'm curious.

This puppy plays by biting, especially around the mouth and teeth. I mean she'll stick her head in there and lick Ryuk's teeth and all around his mouth, usually by way of a running jump so she can reach him. She'll latch on to his ruff and ears and if he turns his back she'll attach to his tail. I know she's not biting hard as Ryuk will correct when she does. Ryuk's tail wags through all of this and he usually responds by rolling her on her back or, when she charges at him, dropping a shoulder and letting her get thrown over his back. His tail is wagging and so is hers. When he throws the puppy he calls her back with a play bow and the play will resume tails wagging.

I've only ever seen such mouth oriented play in a few puppies, though my dog never did it. Is this is a normal play? Why do only some puppies do it? Does it have anything to do submission (I know younger canines often lick the mouth and lower jaw of older individuals. How about my dog? He ONLY rolls rowdy puppies, never small adults even if they're rude. I know physical rolling and pining is not a dog behavior (submission is, but forcing submission is not). He does roll them, but he usually jumps off the moment they're backs are on the ground and waits for them to get up. Then he'll play bow and they play resumes. This behavior seems to be used when the puppy gets to excited and sort of resets them.

So any input? any more information on play behaviors? Observations?