rather odd behavior

Question
I recently acquired a mini dotson who has had no behavior issues since we bought him, however he is not neutered yet. He has never bitten or chewed on anything, people or objects unless it is his toys.  Two days ago we had a small stray female show up and they have become very friendly. From everything that I can tell she has not been spayed. My male dog has tried to mount her several times without success thankfully, but he chews and nibbles on her sides and nipples, I have seen many dogs play together and never witnessed this.  I wanted to know why he was doing this.  We are having him neutered and if she stays she will also be spayed, will he continue to do this to her after that? It doesn't seem to hurt her. I have seen other dog playing around and gently biting a paw or such but never the chewing like he does.

Answer
Mounting is not strictly a sexual behavior.  Dogs mount other dogs (and sometimes people) to make a social statement: dominance, affiliation, attempt to calm, etc.  Your Doxie (I assume that's what you meant by "dotson") is behaving normally toward a "new" dog that suddenly appeared in his environment.  Nibbling (as you describe) is also a sign of affiliation; dogs sometimes do this to humans (use their front teeth in a nibbling manner).  These two are establishing a relationship and it appears to be going successfully.  The hallmark of problem behavior between or among dogs is the level of threat and/or injury.  Most dogs will put another dog "in its place" if behavior crosses the line of comfort.  Have your Doxie neutered ASAP.  Before having the bitch spayed, do a blood study of estrogen levels.  You don't want to spay her when she's too close to her estrus cycle.