HI! I know you posted this question in July but I was reading the responses you got and most of them were from people who don't have a male Boxer themselves! I DO have a male Boxer. In fact, today is his 3rd Birthday. He did not start lifting his leg until well after he turned 1 yr. old. I remember thinking it was strange too! He was probably more like 14 months before he did it regularly. We did not get him neutered because we wanted to breed him and he showed now signs when he was younger that he would lift his leg inside the house. He does lift his leg inside sometimes but only when we are not home! That was why I ended up on this sight in the first place. I was looking for ways to stop his leg lifting and I ended up reading your post first. So happy leg lifting to your Boxer! I just hope for your sake he saves it for outside!