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Re: Velociraptor scavenged azhdarchid pterosaur



On 3/4/2012 1:07 PM, Ben Creisler wrote:

A obvious question is why the Velociraptor happened to drop dead right
after eating the pterosaur bones. One possible scenario might be that
the Velociraptor was already ill or old, and had resorted to
scavenging to survive. I have not seen the paper yet so I don't know
if the taphonomy of the specimen or the health-state of the
Velociraptor individual is discussed.

This would seem to be an issue is various cases of specimens of
predators found with identifiable gut contents.The animal clearly died
or was killed within hours after feeding. If a predator was ill or
old, it might be scavenging because it was no longer able to hunt. In
such cases, the gut contents might not represent the typical diet of a
healthy individual.

Yes. Animals highly adapted to eating bone, as one would expect scavengers to be, can digest bone much more quickly than animals with less acidic digestive systems -- as you imply, stressed individuals in the latter category may not be able to digest a large bone at all.

Thus, a true scavenger would indeed seem less likely to become famous by fortuitously dying and being preserved with a bone in it's gut than an animal that was more adapted to a high-falutin' diet of eggs and soft tissues, but happened to fall on hard times and eat something that eventually proved to be it's immediate cause of death.

This from Wikipedia in reference to a bone-eating bird -- "The acid concentration of the Lammergeier stomach[8] has been estimated to be of pH about 1 and large bones will be digested in about 24 hours, aided by slow mixing/churning of the stomach content."

This implies that (e.g.) a Gypaetus Barbatus fossil with a bone in it's gut that showed no sign of partial digestion would have necessarily died and been preserved within minutes of eating. Even that assumes that stomach acids stop dissolving bone as soon as the individual dies -- which seems unlikely in itself.

Which implies that an identifiable bone preserved in a carnivore's gut could be interpreted as evidence AGAINST a scavenging lifestyle.