Brad,
 
When I read this, I immediately thought of you (as I do whenever I run into the past perfect)
 

As it happens, a team of animal behaviorists led by Jenny Ryon at Dalhousie University had explored this very question of canine's penchant for perfume in 1986. Their study wasn't with dogs—to the best of my knowledge, no controlled studies on scent-rubbing with domesticated dogs have ever been done—but with a very close relative instead: the wolf (Canis lupus).