I've only ever had two male dogs - one before Ripley and now Ripley. My first male (toy poodle) never humped anything and I had attributed that to the fact that we got him as a puppy and neutered him right away. Ripley, on the other hand, was about three years old (a guess) when we got him and he still had his family jewels at that time. We had him neutered right away, but he humps Bella occasionally and she just sits down. I am thinking that he still thinks the testosterone is flowing.