Graphic
Carnivores will eat the soft tissues of the body (especially the face and hands) and
much of the skeleton (resulting in increased decay rate), especially the spongy ends of
the longbones, innominata (pelvis), and vertebrae of both fresh and decayed remains.
When a body has been mutilated by carnivores, it is important to search the general area
for bones that may have been scattered. Carnivores, particularly dogs, are notorious for
carrying bones as far as a quarter of a mile (lh km) from the body and will frequently
carry a skull or other bone back to their owner or neighborhood.
Rodents can cause extensive destruction to the face, hands, feet, and abdomen. The
smaller bones of the hands and feet may be carried away by mice and rats and can usually
be found within a few feet of the body. In contrast, a female opossum and her litter were
noted living alongside a nearly skeletonized cadaver (which was inside a wire cage) for
a period of months without feeding on the desiccated tissue or causing any destruction
to the bones.
If a body is found in a wooded area during warm or hot weather and doesn't show
evidence of carnivore feeding, it is likely that the body was kept in an area not accessible
to dogs (for example, in a warehouse) long enough to allow considerable soft tissue
destruction without concomitant bony destruction, and then carried out and dumped in
the woods. At any rate, if a badly decomposed body is found in an open area (for
example, woods, field, garbage dump) and there is no evidence of carnivore feeding,
other possibilities have to be considered. For example, the absence of carnivore feeding
may alert you that the body has not been exposed to the out of doors for more than a
few days.
Example A few years ago, body parts belonging to a single individual were found in
plastic bags scattered about in three counties in Tennessee. The nearly complete upper
torso was found in a secluded area frequented by neighborhood dogs. Although the body
was badly decomposed (putrefied) and maggot-infested, no evidence of carnivore activity
was present. As the case unfolded it was found that the individual had been killed,
dismembered in his apartment, and, days later, scattered about in the woods. This
explained the advanced degree of bodily decay and insect activity yet lack of carnivore
destruction.
http://library-resources.cqu.edu.au/JFS/PDF/vol_35/iss_1/JFS351900103.pdf
Lots of other discussion regarding decomp factors here. I believe that the girls were out there the whole time, but it could really go either way. If they were still mostly intact, then, it is unlikely that they were out there the whole time. But until we know, it's hard to speculate either way.
(Sorry for the weird format, and I think this might have already been posted, at least in link form.)