User blog comment:ElfieGirl/Creature Question!/@comment-1966944-20120225043031

The series hasn't explained why so, in my opinion, I'd say that the creatures do control their appearance but it may be some type of physical, or mental, "lock down" to maintain control, even in death. The closest example I can come up with is a bird that roosts on a tree at night. When it sleeps, it "locks down" its grip to keep from falling off the limb. Of course, if a bird died, it would release its grip and fall but the creatures may, even in death, be able to maintain their human appearance.