got problem with this behavior ? The big question seems to be WHY do dogs DO “this,” and WHAT can we (humans) DO about it? Some answers, as I see them.
Occasionally, mounting is done to produce more dogs, but in this day and age of the wisdom of neutering, this is hopefully not the case too often!

Mounting is seen often as “play activity” — not to be confused with “foreplay” as this activity is not leading to anything else. Puppies often do this, as do older dogs, and, much to the dismay of the owners, it is NOT limited to male on female behavior! Anyone will do — and often does!

Mounting behavior can also be a show of “who’s in charge” between dogs, i.e., “I’m on top, I’m in charge at this moment, I’ll show you who’s boss!”

The mounting behavior usually bothers the HUMANS much more than the dogs. I suggest that if it is going on in front of guests, just calmly say, “Oh, Fred (or Ethel!) stop being a dog!” That generally implies that the behavior is normal for a dog and that it does not upset you.

The best thing to do is just leave the dogs alone. Don’t speak to them or try to stop them. If the dog on the “bottom” is bothered enough by the dog on the “top,” he will do something about it — growl, whirl around, sit, lie down, etc. If, on the other hand, the dog on the bottom is not doing anything about what is going on, it means that the behavior is not bothering him (her). All that’s left is for the humans to get over it!

The only real concern is dogs mounting humans — hanging onto the guest’s leg, grabbing small children (always keep children OFF THE FLOOR with a puppy or a grown dog – this invites the wrong kind of play.) This type of mounting IS of valid concern to the humans. It is embarrassing and annoying and needs to be stopped. The best bet is to give the dog something ELSE to do. For example, sit and stay or lie down and stay — it is impossible to mount while doing either of these activities! For less obedient dogs, distraction is better. Pick up a toy and throw it or distract him with a biscuit and call the dog away from the person. If the dog persists, put a leash on the dog’s BUCKLE collar (never a pinch or choke for this one) and STAND on the leash. Now the dog can no longer jump up or grab anyone.

Neutering while young is a good idea, but does not always prevent or change the behavior. Humans are always amazed by this — as the dog humps away, the human can be heard to exclaim, “But he’s been fixed” or, “But she’s a girl,” etc. Oh dear.