Rat Terrier becoming snippy

Question
My girlfriend and I have had a rat terrier for over a year, since he was about 8
weeks.  He has been very socialized since the week we got him and has
always been very well behaved and comfortable at our local off-leash dog
park.
Recently though, he has become sometimes aggressive towards other dogs at
the park.  It seems to be linked to certain situations:
-other dogs coming up to my girlfriend and I, particularly when we are sitting
at a picnic table.  The picnic table in general seems to be an area where he
becomes aggressive.
-When we first enter the park, through the gate, and dogs come up to sniff
him.  He does not always, and usually does not, but recently he snaps at the
dogs when they get too close to him as we enter.
-Pugs, bulldogs, any dog with a 'big face' seems to aggravate him.  He snaps
at them with no seeming cause, but will not at other dogs.

Most of the time he is fine and it seems to me that if we do not sit down, he
does not have this problem, but I also recognize that I might not be thinking
like a dog and am just looking for correlation for this problem.  He was NOT
like this last summer, this seems to be a new development.  He is very well
behaved and sweet and home, not possessive, does not chew up our
belongings (anymore), barks very little, not snippy towards us AT ALL.
It might be worth noting that my girlfriend and I recently moved into separate  
apartments, and our dog spends most of his time with her.  We usually go to
the park together.  I don't know if this figures in, but again, it correlates at
least in timing.  PLEASE HELP.  Thank you

Answer
Mike -

A couple of things strike me.  One is that he is now a young adult dog - the time when he is feeling is own macho come into it's highest state - even if he's neutered.

Second, he is definately feeling the split between the 2 of you. They are often sensitive to things that we won't even notice.  For instance, I've been having some trouble with my jack russell who I've had for 5 yrs and adopted as an adult dog.  He started marking in the house for the first time. It totally bewildered me until I realized that each time coincided with a time that I had been around another male dog during my photographic shoots.  So, he was feeling insecure.  I am certain your kiddo is feeling the same way.

What he is doing is called resource guarding - and you are the resource. He does not like any other dogs coming around because they might take some of your attention away from him - and he's feeling very insecure about that.

I would recommend that the both of you take him through an obedience series. Not because he needs the classes, but because he needs extra time with the both of you which entails close contact with you while also being around dogs - in a successful way.  The rewards he earns in class will also reward him for acting appropriately around the other dogs.

Dog parks are not all they're cracked up to be and require a lot of thought about things like insecurity, and how well other people manage their own dogs.  I do not go to them, but have in the past and it was a nightmare. I was thrilled at how well my dogs did, but there were so many set ups for fights that I was shocked.

You also didn't mention if your park separates the small dogs from the big ones.  Big dogs often further set off this kind of reaction in small dogs - again because of insecurity.  Your dog is already insecure, combined with feeling his adult manhood coming to fruitition, and if mixed with an addition of big dogs, it just seems like a set up for him to react in this manner.

Perhaps a hand chosen play date might be more suitable for your little guy.

-Beth