or it might b due to the absense of a U .she might see u as true master n the other ranked below U and thus aint obey ur wife orders n all ..she might b missing the disipline under ur guidance !..
If it is a true bad behavior - Cesar Milan's website is a great place to find out information. My great dane a while back did the same thing, but had a medical problem. He even wet the bed at night. It turned out he had a kidney stone. It seems that if they have kidney stones they will go right then and there, no matter where or who's there. It only gets worse. Going to the vet and an xray will give you the answer if it's medical or behavior.