Shadow does that too. To a pillow or a stuffed animal of my daughters. I just look at him and say "NO"...He usually listens and goes on to doing something else. I have a Black Lab and a Lab Akita mix and they do not hump anything. They are obviously both males LOL I haven't had that trouble with them but Shadow does it whenever he gets a chance to. Hopefully, he will get the picture that it is not allowed?!