LOL it deff puts a smile on my face sometimes the way my dogs behave.Yes luckily I dont have to worry about Tuffy and Crystal fighting..Crystal is very old and probablly didnt have a clue..actually she was probablly sleeping while the incidence took place...NOt like she could of felt anything any lol (hes a pom)heheheh.Anyway what you said makes perfect since because my female pitbull is always mounting my male pitbull.Luckily he doesnt mind it,hes deff the less dominate one in the relationship..(they are husband and wife)
LOL! Humping behavior in dogs is more about dominance than sex. Your pom is simply making it clear that he is above your other dog in the pack order. Generally, it's best to discourage mounting behavior because it can lead to a fight. In your case, if Crystal isn't bothered by it I wouldn't worry about it.
If Tuffy starts humping humans, however, it needs to be made clear to him that he does not "own" humans. Dogs don't care where they are in the pack order as long as they are clear on where that place is. Dogs who hump humans are actually claiming ownership of them. Not a good situation.
Also, when you take Tuffy for a walk, don't allow him to even try to mount another dog or you could have a big fight on your hands.
Don't you just love doggy behavior?! :-)