rubbing on poop..

Question
My male Chihuahua is one and has been rubbing his body against poop he finds outside.  He will ignore other poop laying around, so I wonder if it's a specific, perhaps female dog's feces?  Why do they do this?  He is not neutered if that helps.  

thank you so much,
barbette

Answer
All dogs do this, its nothing unusual.  They quite like fox poop and cat poop generally because it smells strongly.  Who knows why they do it - dogs just being dogs like strong smells and think their "perfume" is great.  
I strongly recommend tomato ketchup as a house-hold necessity.  A ketchup bath takes the smell out better than anything else I've tried.
Hope this helps.
Sarah