I've been noticing that my dogs seem to not want to both sleep on my bed at the same time, one is a mid sized terrier and the other is a small 10lb lapdog so it's not a space issue. Just now one of my dogs was sleeping on the floor on a dog bed, the other sleeping on my bed before he left to go outside. I make a coffee before heading back to my room and notice the floor dog has stolen the spot that was previously occupied.

I've even had issues before with my bigger dog guarding resources and trying to monopolize everything in the house but seemingly even she respects this honor code that only one dog can be on the bed at a time and first come first serve. Why would this happen?