[Nancy1999]

Marking is caused by the hormone testosterone, and while the testes make the bulk of testosterone, the adrenal gland makes s some as well. This can vary considerably between dogs, and your dog's adrenal glands are making enough testosterone to produce marking. If you only had one dog, the adrenal glands probably wouldn't have kicked in so much, but another dog and the smells they produce can cause the adrenal glands to make extra testosterone. A couple of things you can do that might help, use a spray with enzymes, on all accidents. Natures' Miracle is a good one, and give it time to work, and repeat. You can even use a "black light" to see if any odor is left in the couch as they protein smells will cause the dog to return to the spot. I take Joey for walks and he's allowed to mark outside, and I think this helps keep him from marking inside. We have my sons' dogs visiting regularly and they are inclined to mark, so Joey's tempted, but the walking helps prevent marking inside. If all else fails use belly bands!