Re: Hadrosaur Defense

["Richard L. Dieterle" <Richard.L.Dieterle-1@tc.umn.edu>]

It has been suggested that Hadrosaurs could find protection in herds, and to 
bolster the claim, proponents have adduced models drawn from mammalian 
counterparts.  But are they really counterparts in any rich sense?  Most mammals
that we think of in this connection are quadrupedal, hoofed, and fast.  Their 
being quadrupedal allows them to kick with their pes even while fleeing, and to 
stomp with their manus when attacked from the front.  The hooves often prove to 
be very effective weapons, so much so that elks, deer, caribou (& cet.) are 
rarely attacked by wolves unless they are weak from age or sickness; and when 
cornered, they generally make good use of their hooves in preference to their 
antlers (which are more intraspecific).  The only corresponding behavior that 
could be performed by a Hadrosaur would be to leap onto a small carnivore with 
both feet, relying on weight to deliver a crushing blow.  Mobbing behavior might
work in this context, although it is not clear that it would work too very well 
against a pack of carnivores.  Also the agility of the carnivore could make the 
behavior a more nearly suicidal gamble.  

In thinking about animals that seem to be practically defenseless, the seal 
comes to mind.  We can say in certain limited respects that -- T. regi (etc.) : 
Hadrosaurs :: sharks : seals.  When a shark attacks a seal, the sealÕs chief 
defense is maneuverability.  I donÕt believe that a seal can ÒoutrunÓ a shark, 
but instead takes advantage of the sharkÕs greater speed to perform a tight 
turning maneuver whose best analogy is to be found in fighter aircraft Òdog 
fightsÓ (an unfortunate simile in this connection).  Antelope have to rely on 
similar tactics when attacked by cheetahs.  

There is another interesting possibility.  Among mammals, most large predators 
can run faster than prey over a short distance, but over a longer course cannot 
sustain the effort.  (The reverse can be true in a smaller predator like a dog.)
Although Hadrosaurs were not too fast, perhaps they were able to sustain their 
flight for long periods of time, so that if they were given a short lead, they 
could exhaust their pursuers.  This might help explain their peculiar long nasal
passages: whatever other function they may happened to have had, they could also
have been the functional counterparts to RTs, conserving moisture in long 
Òstampedes,Ó and giving them the ability to outlast their predators.  

It seems to me that the question of whether they could leap well enough to pose 
a hazard to smaller predators (and thereby defend their rookeries), and whether 
they could be described as more agile than large contemporary carnivores, are 
questions that can be addressed to some degree by their osteology.  

Richard Dieterle