[Rayneiac]

How old is Pete, and how long has this been going on?

Just because he's not destroying everything in sight or having bladder issues doesn't mean it CAN'T be SA. Each dog will exhibit traits of that differently, just like each person will exhibit different traits of anxiety if it's an issue for them.

You mention 'we'...implying there are multiple people in the household. How about some experiments? One person hides, say in a room Pete can't see. The other leaves...and the person who stays behind can observe a bit of what's going on. Anything stimulating the barking? What sort of barking? (different barks can mean different things). What other things is Pete doing? (jumping in crate, trying to claw his way out...etc)

 

[Rayneiac]

I'm going to have to go with some sort of anxiety here.

Is it possible to find out anything about his life prior to living with you? Info might be useful.

 

[Rayneiac]

Look at this from Pete's possible view. "I had a home once upon a time..then I lived on the streets. No family, no affection...I was scared. Then I had a home again for a while. Now I have another new home."

It's been said often that dogs take from a couple of weeks to a couple of months to 'settle in' at a new home, learn the ropes etc. He may be partly confused, partly wondering when is this 'home' going to change and partly scared. As in scared that these humans he's getting attached to and bonding with may change....AGAIN.

Perhaps work on this like it IS SA, and help Pete learn (or re-learn) the skills he needs to be a balanced dog. I'm sure he can do it. But anxiety is a scary force of nature in humans even with our logical and analytical brains. Imagine the multiplied effects to a dog.