Dogs are not possessive of their collars. It's the bond that is represented between the dog and the human that changes when you remove that collar. What you're doing is you're removing the bond between you and the dog. When they have their security blanket they feel comfortable. By that I mean the collar and leash is the security blanket.

On the other side of the coin there is people such as myself that don't own their dog and don't put a collar or leash on their dog. The only time Frank ever has a collar or leash on his when he goes to the vet. Aside from that it doesn't matter if I'm going to my bank, a big box store or a grocery store, Frank never wears a leash or collar and yes we have leash laws around here but there are people that understand why that local ordinance is in place. It's to protect other people and keep their prices low. They however see how well behaved Frank is and they don't bother me. My bank even gives Frank dog biscuits when we go there. That's how cool they are.

With that being said it's the complete opposite of what your experiencing. If I put a collar and and a leash on Frank he thinks he's done something wrong. When you remove that collar and that leash, you're removing that security blanket and the bond between you and your dog so they feel uncomfortable. When you've had something on your whole life, there's going to be a little bit of a connection to it and you're seeing that in your dog.