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Re: Velociraptor scavenged azhdarchid pterosaur

On Mar 4, 2012, at 12:45 PM, Denver Fowler wrote:

> Birds of prey will fairly commonly take prey that are subequal in size to 
> themselves (which would be the case with a 13kg Velociraptor vs a 9kg 
> pterosaur). Peregrines take a lot of pigeons, hawks take rabbits; 
> accipitrines take all manner of large birds their own size, or sometimes 
> slightly larger. Flight has little influence on the hawks and accipitrines as 
> they take prey on the ground, and other than being typically rather surprised 
> have plenty of fight left in them. If you take "large" prey (subequal size to 
> the predator; that cannot be contained within the foot), the issue is how do 
> you immobilize an animal that might retaliate? 

I was expecting that birds of prey would get mention in the discussion.  Yes, 
birds of prey do take large prey items.  However, I assert that your 
supposition regarding the unimportance of flight in this regard is mistaken.  
Most birds of prey do take prey on the ground, but that hardly removes the 
importance of flight.  The ability to fly removes a huge component of the risk 
in attacking large prey.  A bird of prey has a very high probability of escape 
if the initial attack does not subdue the prey item as expected.  The critical 
detail here is not what happens when the attack is successful, but what happens 
when it fails.  Most attacks on large prey fail, but those failures likely 
carry relatively low risk if the predator can fly and the prey item cannot.

> Our 2011 paper described the RPR behaviour that facilitates such attacks (for 
> which comparable anatomical specialisations are lacking in extant mammalian 
> predators), and we specifically note that dromaeosaurid anatomy seems 
> increasingly adapted towards "large" prey RPR strategies. In this paper we 
> agree that predators will typically take prey smaller than themselves, but 
> really this was more a response to the idea that deinoonychus (et al) were 
> somehow always killing sauropods/tenontosaurs (although note the ability of 
> golden eagles to take down sheep; also in the paper). When bodymasses are 
> more closely matched, it may not be as much of an issue.

For those reading, the URL for Denver's 2011 paper in PLoS ONE is: 

In any case, your point is well taken, but the RPR behavior is applicable (as 
you noted above) to any prey that cannot be easily contained within the foot.  
So even in a case were the prey was, for example, 20-25% of the mass of the 
predator it would count as "large", and your model would be potentially 
applicable.  I am not necessarily arguing that dromaeosaurids did not eat 
larger prey than average, only that a specimen of a Velociraptor preserved in 
the midst of having the snot beaten out of it by a Protoceratops that probably 
greatly outweighed it in life should not be taken to mean that dromaeosaurids 
routinely attacked prey substantially larger than themselves.  Suggesting that 
a RPR strategy might have allowed predation on animals 50% of the predator's 
mass does not stretch incredulity in the same manner as the assertion that 
mid-sized theropods went around beating down sauropods or that dromaeosaurids 
went berserker-style after prey 400% of their own mass or more.


--Mike Habib

Michael Habib
Assistant Professor of Biology
Chatham University
Woodland Road, Pittsburgh PA  15232
Buhl Hall, Room 226A
(443) 280-0181