Territories and Boundries
As a real young canine pup, they will associate themselves with their territory. A canines territory has boundaries depending on the age of the dog and the experience of the territory. A pup will claim his immediate territory wherever he is ANCHORED ... say fore instance the crate /den... or wherever you put him to do his business.
Marking his territory is the same as claiming his territory and the smell shows the pup where his boundaries are... instinctively they have an invisible amount of space or circumference which is based on where the ANCHOR is.
Your pup has the boundary set to the doorway right now (when put in your bedroom). He will venture out of the doorway as he explores... If you wish to take him out of his comfort zone, you must do this by carrying him. You now will be the ANCHOR or he may claim an object which would shelter him from a hawk attack or such things..
All this is prehistoric instincts... You can use this to your advantage when training your pup. I make sure that the pup is ANCHORED to me by going places where he can claim nothing else but me.
Because they hone in on objects such as caves, under brush and other objects that are low to the ground, I get as low to the ground as I can so that they can climb under my knee or between my arms and the ground. Soon he will be coming to me when called and like I said ANCHORING (tm) to me.