Predation categories (per Dr. Holtz)

[Tim Madden <TMADDEN@medicode.mhs.compuserve.com>]

> I REALLY hope someone saved my carnivore predatory technique posting, so
> they can send him the appropriate part of the message.  ;-)

I did, and I hope nobody minds if I repost it to the mailing
list in general, for all those who might have missed it.

>  ----------
> From: dinosaur
> To: Multiple recipients of list
> Subject: Predation in T. rex and other theropods
> Date: Tuesday, November 29, 1994 9:35AM
>
> [I tried to stay out of this as long as I could.  I really did... ;-)]
>
> Since I have done some degree of research in this field, I thought I ought
> to state my conclusions/opinions on the subject of Tyrannosaurus 
> predation:
>
> Among large modern terrestrial hypercarnivores (a useful term mammalogists
> use for animals which derive >95% of their food in the form of vertebrate
> flesh), there are three major predatory repetoires:
>
> 1) Grapple-and-slash.  Best typified by modern felids (cats), these are
> predators characterized by highly compressed, recurved, blade-like claws 
> on the hands and feet; relatively short and powerful limbs; and tails used
> as
> dynamic stabilizers to allow for quick turns.  Grapple-and-slash predators
> are for the most part ambush predators, which seize the prey with the
> forelimbs after a very short chase.  The prey is then dispatched with a
> combination of slashes from the forelimb, disemboweling kicks with the
> hindlimb, and bites and/or suffocation with the mouth.  Grapple and slash
> predators are not particularly fast in the long run, but are good for 
> short acceleration.  [And for some reason, Jack Horner seems to think that
> this is the preferred form of predation, despite it being limited today to
> only one major group, the Felidae].
>
> 2) Grapple-and-bite.  Best typified by modern raptorial birds, these are
> predators characterized by claws which are curved but fairly round in
> cross-section.  These claws are at the end of fairly powerful limbs.
> Grapple-and-bite predators today are for the most part ambushers ("death
> from above"), which seize the prey with the forelimbs, dispatching the 
> prey with bites to the neck or back, and flying away with the carcass to 
> eat elsewhere.  The claws are used primarily for holding prey, while the 
> jaws are the main killing tool.
>
> 3) Pursuit-and-bite.  Typified today by canids (dogs, wolves, etc.),
> hyaenids, the cheetah, and in the recent past by flightless predatory
> birds.  The claws of pursuit-and-bite predators are for the most part not
> highly curved and are rounded in cross-section.  These predators do have
> powerful jaws and necks, long teeth, and relatively long limbs.
> Pursuit-and-bite predators characteristically run down their prey after a
> fairly long chase, seize the prey in their jaws, and kill the prey with a
> combination of biting and suffocation.  The claws, if used at all, are 
> used to stabilize the victim so the jaws can do their work.
>
> Comparing theropods to these repetoires, it is fairly easy to relate
> different groups to the three catagories.  Dromaeosaurids are excellent
> candidates for grapple-and-slash predators, since they proportionately
> short and stout legs (forget ever reference you've seen to Velociraptor 
> and Deinonychus as being "swift" as dinosaurs go.  Even Tyrannosaurus rex
> has proportionately longer lower legs and feet than do these smaller 
> forms). The claws of the hand and the sickle-claw of the foot match the 
> proportions and angle of felid claws very nicely, and the tail of 
> dromaeosaurids has been known to be a dynamic stabilizer since 1969.  And
> of course, the fighting Velociraptor specimen is in classic 
> grapple-and-slash predatory attack, inculding the disemboweling kicks to 
> the belly of the Protoceratops.
>
> Most large theropods (allosauroids, megalosauroids, Dryptosaurus, etc.),
> match some variation on the grapple-and-bite theme.  The hand claws of
> these animals closely match the proportions and angles of predatory birds,
> and are at the end of short but powerful arms.  Like predatory birds, 
> these claws were probably not the primary weapons of killing, but were 
> used to seize and hold the prey while the jaws did the work.  Note that it
> is these animals, and not dromaeosaurids, which match modern "raptors" the
> best.
>
> Tyrannosaurids fit well with the pursuit-and-bite catagory.  Like canids
> and hyaenids, they have proportionately long legs (T. rex itself has legs
> which are more "cursorial" than the man-sized herbivore Dryosaurus and
> other accepted runners), very powerful jaws, and claws of the hand and 
> feet which are not highly curved and rounded in cross-section.  Although 
> they may not have pursued prey for wolf-like distances, the body of 
> anatomical evidence points to the adaptations of tyrannosaurids as being 
> predatory, and specifically pursuit-and-bite predatory, features.
>
> And as for scavenging - none of the alledged scavenging features suggested
> by Horner holds up in quantitative or comparative analysis.  His claim
> that predators need to use their forelimbs in prey acquisition does not 
> stand the test of observations of the modern world.  Tyrannosaurids show 
> more cursorial adaptations than any other large Late Cretaceous 
> Asiamerican dinosaur (hadrosaurids, ceratopsids, ankylosaurids, etc.), so
> they probably were faster than any of these.
>
> BUT...  as others have already pointed out, scavenging and predation are
> not mutually exculsive behaviors.  In some regions of Africa, for example,
> lions are predominantly scavengers and hyaenas the major predators, while
> in other parts of the same continent, these roles are reversed.
> Tyrannosaurids would be in a good position to bully any other theropod 
> away from a corpse (dromaeosaurids arguably may be more deadly pound for 
> pound, but tyrannosaurids had a LOT more pounds...).  It is not 
> unreasonable that certain individual tyrannosaurid populations, or even 
> species, may have gotten most of their food from carcasses.  Nevertheless,
> the anatomy of tyrannosaurids indicates that they were capable of 
> dispatching prey using techiniques grossly similar to those used by 
> canids, hyaenids, and the like  - running down animals, seizing them in 
> their jaws, and ripping out huge chunks and/or suffocating the prey item 
> until it was dead.
>
> Thanks for your time,
>
>
> Thomas R. Holtz, Jr.
> tholtz@geochange.er.usgs.gov
> Vertebrate Paleontologist in Exile                  Phone:    703-648-5280
> U.S. Geological Survey                                FAX:    703-648-5420
> Branch of Paleontology & Stratigraphy
> MS 970 National Center
> Reston, VA  22092
> U.S.A.