I gotta know...why on earth are you asking US??? What is it about Oprano (collectively) that makes you believe that Opranauts would be good at disposing of dead bodies?
I think you need to be careful of the carnivore theory too...most likely something would remain, probably the teeth. And they can get DNA from the centre of the tooth (which is also not destroyed if the body is burned beyond recognition). Even if the carnivore did swallow the teeth, they would not be digested but pass out thru the body, and potentially could be found in the droppings (and then DNA tested).