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Just some idle rambling on the theropod
scavenging hypothesis. As a mammalogist I'd point out that in no extant
terrestrial system and few, if any, fossil communities, do the largest
carnivores exist wholly or even mostly on carrion (unless you include male lions
- but even this has recently been contested). Of course it all comes down to
semantics at some point, because no known carnivore is completely averse to
scavenging and no so-called scavenger will turn down an easy kill if it
can make it.
Among mammals - tooth
morphology strongly determines an animal's capacity to fully process a
carcass - typically, the ability to crush bone (evidenced by large, blunt cusps)
is associated with scavenging. The problem here is that the most specialised
living mammal in this respect, i.e., the spotted hyaena, although an adept
scavenger, generally derives the bulk of its requirements through predation. The
take home being that while we can reasonably deduce that fossil
mammals whose dentitia were dominated by large bulbous cusps
regularly consumed more of a carcass than other taxa - we can't assume that ipso
facto, that they were mostly scavengers. Given the near impossibility of making
such calls with respect to mammals whose well-differentiated teeth provide an
excellent window into diet and behaviour, what are the chances with respect to
dinosaurs whose, dentitia, while admirably well-adapted, are generally far more
homogenous?
With respect to the sense of smell - tell me where
I'm going wrong, but I'd have to say I can't see what the fuss is about -
theropods may or may not have had great senses of smell and eyesight -
and elevating the sensory platform may or may not provided some
advantage - but because the senses can be equally as important to a predator as
a scavenger it really has little no baring on the argument.
To conclude this little rant - the suggestion
that tyrranosaurs must have been scavengers because their little forelimbs were
too weak to grapple with prey seems deeply flawed and the product of an
anthropocentric mindset. Sure, many extant predators use their forelimbs to
subdue prey, but then many don't.... canids are an obvious example among
mammals, but perhaps more relevant to this argument are crocs, varanids and
birds. Of course, big cats, the most formidable of living terrestrial
predators use their forelimbs extensively when taking large prey- but then these
animals lack the dental and cranial hardware to produce devastating and lethal
wounds on large prey without the precision affected by powerful forelimbs (the
same can be said for sabre-tooths). Another factor of relevance is that felids
can't afford to damage or lose their teeth. These caveats just don't
hold true for varanids or crocs and even less so for
tyrranosaurs.
Personally, I think that tyrranosaurs were whatever
they wanted be (making them excellent spokes-animals for sports-shoe Co.s)
- as the biggest baddest kid on the block with replaceable teeth and
an awesome delivery system equally well-suited to killing or
carrion-feeding, they could muscle lesser beasts of carcasses or take live prey
as the situation demanded and I don't doubt that they did both.
Shoot me down if you will.
Cheers
______________________________________________________
Dr Stephen Wroe
HOMEPAGE - http://www.bio.usyd.edu.au/staff/swroe/swroe.htm
Institute of Wildlife Research, School of Biological Sciences (AO8) University of Sydney NSW Australia 2006 Email: swroe@bio.usyd.edu.au; Email: thylacoleo@optusnet.com.au Ph. 02 9351 8764; Ph. 02 9702 6435 ______________________________________________________ |