Female puppies mounting each other

Question
I have 2 four month old cocker spaniel female puppies from the same litter. You recently helped me with the aggression/dominance issue and they are responding to the can and pennies, most of the times. However, sometimes during these episodes, one or the other mounts the other and displays male humping sexual behavior. Is this also a sign of dominance? and should I be worried about this behavior?

Answer
Yes it's definitely dominance.  Carla, the can of pennies is an effective stopgap but they need "real" training and I strongly suggest classes for the basics.
Also..at 4 months they need a ton of exercise and I have a feeling they're so wired because they're not getting it.
A tired dog is a good dog.  If you get the National geographic channel, start watching Cesar Milan.  His credo is exercise - discipline - then affection.

Also, they shouldn't be reacting to the can of pennies "most of the time" if you're doing it correctly.
Bring that can down "hard" for one shattering noise..say NO...move towards anyone still looking defiant.  NO conversation - no praise for stopping.  Just walk away.

The message here is that you'll let them work out their pack order "to a point" but no real aggression is acceptable.

Never let them walk out the door in front of you.  Make them sit with leash on until they're calm.  Never feed them without making them "sit".  Nothing is free !

At home tie a leash to your belt loop and "where you go, the dog goes".  No conversation.  Message:   "I'm the pack leader so you'd better watch me".

If you don't start taking control and doing some serious training you're going to end up very shortly with two unmanageable dogs.

Also they should very shortly be getting spayed.
Delores