RE: theropod scavenging

["Williams, Tim" <TiJaWi@agron.iastate.edu>]

"no go" wrote:

>>I basically argued that tyrannosaurs (and other big theropods) could
>>have capitalized on being tall bipeds in detecting carcasses by smell
or
>>sight, having an advantage over carnivores whose heads are closer to
>>the ground.

If the behavior of modern birds are anything to go by, then scavenging
theropods of the Mesozoic may have relied on visual acuity rather than smell
to detect prey.  Very few modern birds have a good sense of smell; kiwis and
a few species of vulture (cathartids, including the Turkey Vulture mentioned
by Dan) come to mind.

The "tyrannosaurs-were-scavengers" idea seems to stem from two assumptions:
(1) tyrannosaurs could not be predators because they were too slow to chase
down prey and too big to ambush prey (where would they hide?); and (2) the
diminutive forelimbs indicate loss of predatory behavior.

Both these asumptions have been convincingly refuted.  (1) Tyrannosaurid
hindlimbs and feet were actually very cursorial (one professional
paleontologist has actually done rather a lot of work on this; he actually
posts regularly to this list).  (2) Tyrannosaurid forelimbs, though small,
were nonetheless invested with an impressive amount of musculature and
mobility, suggesting they were used for *something*.  I like Carpenter and
Smith's idea that the arms were used to clasp prey close to the
tyrannosaur's chest while (or after) the jaws went and feet went to work
subduing the prey.

Many modern predators do resort to scavenging occasionally; why turn down a
free meal? (hygienic considerations aside).  Similarly, many carnivores that
derive most of their meat from carrion do attack small prey on occasions;
though some species never do.

Maybe tyrannosaurs did scavenge on carcasses; but arguing that this is the
*only* way these theropods obtained flesh is a real stretch.  Heck, just
look at those jaws and teeth!



Tim