Mine don't know what a collar is either. The tags that we have are small, they are hooked on one of the harness loops. The tag has a plastic frame over them so there is no dingling as they walk, the furbabies don't even know its there.
However I heard about a yorkie in another neighborhood ... who had gotten out of the home, a man driving by saw the dog, stopped on the side of the road to motion the yorkie to come to him, the dog went along to the car, a neighbor saw this happening, but the man in the van told him, hey, this is MY dog and took off with it, the collar with the tags were ignored or thrown away by the "NEW" owner, so having tags on a collar doesn't always bring the dog back home
. I am rethinking .... perhaps I will micro chip.