They feel as if they have to protect their pack and property, and even themselves sometimes, but they don't really want to.
The usual solution is for them to see that you are in charge, and that the dog doesn't need to be. That you are handling it. Perhaps, by putting up what you have, you have handled it in his mind, and he can now relax. Or, he draws a line in his mind that says that what he can't see is less of a threat.
I'm glad that it's working out so far.
How big is mama dog? Are they big pups?
Love All Life, Thank You For Posting! :)