Since Gus was a pup he would always hump things-like my slipper.
Now he is 8 months and anytime a dog wants to play with him, he wants to hump them.Male and Female. It's kinda embarrassing and I try to joke with the other dog owner but is there anything I can do to teach Gus how to play instead of hump?
He's a very friendly GSD and loves dogs and people but has little experience in real play time with other dogs.
Any suggestions will be helpful.
Thanks, Kathy

Why are you letting him "play" with unknown dogs to begin with?

Either he is A) becoming sexually aware or B) expressing his dominance... either of which can turn into a dog fight if he picks the wrong dog.

This is where you have to be the mom on the other end of the leash and call the shots.

The action you describe is an act of dominance and occurs in male and females. You state dog has displayed this behavior since a small pup; ie--your slipper; he chose this object as his conquest. Now..getting older he is also "coming into himself" and will probably continue this behavior if left uncorrected. This can be a big problem if you allow this behavior to continue; especially if he decides to "dominate" an unreceptive unfamiliar dog that you are allowing him to "socialize" with.

A male/female adult that will hump (female or male) is dominate and usually high in rank within pack order. If another dog trys to hump him/her; this is a direct threat to position within the pack. Keep in mind..whenever your dog is in the company of other dogs...a type of "pack" occurs.

I had a 25lb Spitz/Sheltie male that would sneak up behind my 85lb female GSD or 65lb female Husky/GS when they were sitting..just hanging out. He would hump...then run like the wind to other parts of the yard before the females could get to their feet. In this case..it was a game that he played but the high ranking females didn't see the humor in it and would be quite annoyed. However; they were all housemates and knew the "strike of Freddie" was harmless.