We adopted our one-year-old dog, Kopa, who was neutered a little over a month before we adopted him. Within the first few hours of bringing him home, he marked in the same room three times. He was used to being an outside dog, so when he had free roam of the house, he was ready to declare everything his own by lifting his leg. To say we were frustrated with his marking was an understatement. We knew that this was an instinct for him, but cleaning up the messes was a nightmare for us. How do we stop his marking so we can trust him in the house? Here are some tips on why dogs mark their territory and how to stop it.