Defacating on the window seat

Question
Newly adopted rescue 3-yr old Papillon joined our household of 3 other Paps (one is alpha female).  This little guy knows to go outside.  He will hit the doggy door flying and go do his business when I am there to remind him.  But, during the day, the sunroom is home to all 4 dogs with a doggy door to a very secure area.  But, the newbie wants to poop on the window seat cushion - of course this is where the others frequently lay.  I don't know what to do to stop this, other than to crate him.  I do have crates in that room, but mine have always had free run of this room (concrete floors) and they are pad trained when the weather is extreme.  Any suggestions - should I crate only the newbie.  I do not want to punish the others.  Also, the newbie is full throttle ahead all of the time, and the others are thinking about the next siesta.

Answer
This really sounds like a pack status thing.  Neuter him if not already.  The key to most behavior problems is approaching things using the dog's natural instincts.  Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog.  Life is much easier if the 2 legged pack members outrank the 4 legged ones.  You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at http://www.dogsbestfriend.com/  For more on being top dog, see http://www.dogbreedinfo.com./topdogrules.htm

If none of that helps, then crate him.