Hmmm, okay that clears that question up.
o, the next one is- how is he secured during travel? Are you using any type of restraint in the car, like a seatbelt? Our eldest dog (she passed at 19 this summer) had the shaking/panting issue when traveling until she moved in with me and learned to wear a seatbelt- we also use a seat hammock so that falling between the seats is impossible. I know that won't work in public transportation- but how ARE you securing him when riding the bus or subway? Is he tucked on the floorboards between your feet? Next to you?
Have you tried anti-anxiety meds? (valium or alprazolam)
I can't shake the feeling that since it has worsened since you have had him, that is IS something you are inadvertently "training" him to do...
If he were my dog, I would probably do a consult with a behaviorist, just to get an outside, in person perspective. They might be able to see what it is that you are (or aren't) doing that is causing the issue.
I'm certain it's his lifestyle change, he gets to go out more and explore the world
his previous owner only had him in the car a couple of times.
I have tried many different restraints: harness, crate, me in the back holding him, even keeping him in a down position. I have also tried letting him loose (made it worse).
On the bus and subway I've tried: letting him walk around, sit in front of me, stand with head on lap, lay down, tucked under my seat.
The ones that worked the best was tucked under the seat, or head on lap. Also, if the subway or bus was packed, he calmed down, and would be perfect the whole ride.
I should also mention, all this worse behaviour has popped up when his thyroid levels dropped. We are now in the process of getting it back up.
If this doesn't get better, I will have to consult a behaviourist.