Tink, I don't think it is psychological, at least not in a "I'll show them" kind of way...it may well be acting out due to the well thing...but I would say that he is marking.
That is the only time that Chase marks, when he has a litter of his pups around. It makes me so mad...but then I remember reading that what it means is that he is "making it known to the dog world" that this is his property, his territory and his family...and he will protect it with his life." I think that is kind of sweet...even though I hate the problem, I love the message!
When the pups are gone, I am sure that Moses will get back to normal. Chase always does.