Raptors: do they live up to the hype?

[Infinity Blade]

I came across two blog posts (two parts that is) some time back when Thomas R. Holtz Jr. gave a link to them somewhere on Twitter that both explore if dromaeosaurid dinosaurs truly lived up to their present day hype. The author gives his opinion on the physical capabilities of these dinosaurs and whatnot.

accpaleo.wordpress.com/2015/06/05/raptors-do-they-live-up-to-the-hype-part-1/
accpaleo.wordpress.com/2015/06/06/raptors-do-they-live-up-to-the-hype-part-2/

What are your thoughts?

[Cross]

I'll be the first to contribute to this thread.
Firstly, the possibility of cooperative hunting can't be ruled out with a simple "A Deinonychus bone bed proves nothing" argument.
Bakker (1998) pointed out that the most abundant herbivore in Aptian-Albian North America was Tenontosaurus, and that it was likely impossible for a single Deinonychus to subdue one.
Of course, there is Acrocanthosaurus, however, the deep, ventrally facing paroccipital processes and serrated dentition, as well as the narrow, V-shaped skull with a modified quadrate suggests that it was a common predator of sauropods, not ornithopods (i.e It was adapted for brontophagous behavior).
Acrocanthosaurusis clearly specialized to a brontophagous niche, and it clearly is not a generalist hunter of any contemporaneous herbivores like say, an abelisaur. That just leaves the title of "Predator of Tenontosaurus[/i" to Deinonychus. And of course, the only way they could subdue or kill a Tenontosaurus is if they gang up on it like what some crocodilians do to buffalo and wildebeest, or what small canids do to ruminants, and what varanids do to cattle. In "The truth about killer dinosaurs", they even observe cooperative behavior in Harris Hawks (though they were hunting a rabbit). All modern archosaurs are capable of hunting cooperatively, so there's no reason to conclude that some theropod dinosaurs couldn't do the same.





I also have my own hypothesis for the predatory behavior of dromaeosaurids. Looking at their functional anatomy, I think that they engaged in arboreal raptorial cooperative hunting. The large ungual claw on their digit-II may have assisted in scansorial behavior (climbing vertical surfaces), and they may have also employed wing-assisted incline-running during tree climbing. Stalking prey from the canopy is a very effective way of ambush, and attacking from height may create momentum when the animal pins its prey to the ground, creating a truly raptor-like method of predation, and there's also no reason to assume that they couldn't have done this cooperatively like Harris Hawks or Varanids do.

Fig 1. demostration of wing-assisted incline runninng :


Arboreal cooperative hunting demonstration courtesy of BBC's Sinornithosaurus : www.youtube.com/watch?v=8-jpuywa6lg


So my verdict : Jurassic Park wolf raptors? No. Ninja tree-stalking, gliding, arboreal, ambush attack, stealth raptors? Yes.



References :

1. Fowler DW, Freedman EA, Scannella JB, Kambic RE (2011) The Predatory Ecology of Deinonychus and the Origin of Flapping in Birds. PLoS ONE 6(12): e28964. doi:10.1371/journal.pone.0028964

2. Bakker, Robert T.: Brontosaur killers: Late Jurassic allosaurids as sabre-tooth cat analogues. Gaia, Vol. 15 (1998); pp. 145-158

3. Manning, P. L., Payne, D., Pennicott, J., Barrett, P. M., & Ennos, R. A. (2006). Dinosaur killer claws or climbing crampons?. Biology Letters, 2(1), 110-112.

[theropod]

I think the blog posts aren't a particular novelty, but I don't agree with them on some accounts.

Firstly, speed. I think this may just have been phrased in an ambiguous way. When hunting small animals, agility (maneuverability and acelleration) are much more important than sheer top speed, and the former is what dromaeosaurs posessed, while the latter they likely did not have in particular quantity, owing to un-cursorial hindlimb proportions.

Secondly, limitation to small prey. Most predators rely on prey smaller than themselves, and that is what Fowler and colleagues meant. Accipitrids, however, the analogy used by the study in question, also take very large prey on occasion-they just don't use the method of pinning it to the ground with their body weight. Dromaeosaurs were probably capable of the same. Of course that doesn't mean the image of dromaeosaurs (or any theropod for that matter) as spending all their time viciously tearing some vastly larger hervivore to pieces is accurate, because it most certainly isn't. But no reasoning has been provided to suggest they were more limited to small prey than other predators.

Thirdly, gregarious behaviour. As luigi already pointed out, absence of evidence (if indeed that's the case) is not evidence of absence. Furthermore raptors, the aforementioned closest analogue, and even lizards and crocodilles can cooperate to a degree, so I don't see why dromaeosaurs shouldn't, even though the extremes to which wolves are social may not be the best comparison.

Even though Acrocanthosaurus certainly did not only prey on sauropods, I have trouble believing that Tenontosaurus had only that one predator when there were others with a functional morphology consistent with preying on it, and the same way I have trouble believing that the already remarkable case of preservation that is the fighting dinosaurs fossil just so happened to record a very unusual behaviour.

Finallly, bite force. Let's just say that a smaller brain leaving more space for jaw muscles simply doesn't negate the fact that the jaws and teeth are not sturdy enough to deal with bone-crushing, Alligator-esque bite forces, and that's what any functional anatomist would tell you.

[stomatopod]

I find the intelligence part funny. Orca luring the bird with a fish. Crocs do the same with sticks.

[creature386]

The first blog post seems to be mostly a restatement of Farlow's hypothesis which mostly made valid counterarguments to the mainstream-view of raptors, but without ruling out big game hunting. Some sentences in fact support the idea:

Gradual divergence of foot proportions within Deinonychosauria is potentially indicative of ecological separation between Dromaeosauridae and Troodontidae as large and small prey specialists (respectively).

As for gregarious behavior, a bit sad that they only discussed Deinonychus, there is other evidence:

Multiple parallel and closely spaced trackways generated by the larger track maker provide the best evidence yet discovered for gregarious behavior in deinonychosaurian theropods.

link.springer.com/article/10.1007/s00114-007-0310-7
One of his arguments appears to be the rather dubious premise that raptor intelligence was not comparable to avian intelligence and backing up a dubious statement with another dubious statement sounds a bit like circular reasoning.

While it is of course not irrational to assume raptors were no gregarious big game hunters (so much double negation in this sentence), it is still a bit weak to call the opposition dinosaur fanboys.

[coherentsheaf]

Jun 24, 2015 19:21:42 GMT 5 stomatopod said:

I find the intelligence part funny. Orca luring the bird with a fish. Crocs do the same with sticks.

The interesting question: How much of such behavior is instinctual?

I recently heard the plausible suggestion that much of the tool making behavior of early hominids was genetic, based on the fact that there was little variation in tools formillion of years! If something as complex as the advanced tool use of homo errectus could be instinctual, certainly stuff like luring in birds could be as well.

[Cross]

Dromaeosaurids also have shorter and more robust metatarsi compared to acrtometatarsalian coelurosaurs (take note : dromaeosaurids aren't arctometatarsalian theropods).
If anything, the robust MT-1 pedal bones, when compared to troodontids, suggest that they sacrifice cursoriality for gripping power and agility.
So looking at the foot morphology of dromaeosaurids, their pedal digits and claws clearly serve a predatory function. Scansoriality appears to be only a secondary function for their enlarged ungues.

[theropod]

^What you are noting could also derve for scansoriality. But if that were all they were specialized for, I’d expect a different claw morphology (the curvature often fits, but is too variable, and the lateral compression looks more like something built for killing) and probably other modification in the overall built. Also, the largest dromaeosaurs are simply too big to be scansorial, but still have similar pedal anatomy.

[coherentsheaf]

Even Deinonychus is probably too large to be scansorial.

[Deathadder]

Do any of you think it's possible that in some species of dromeosauridae like deinonycus could possibly glide or climb trees when young?

[blaze]

There is a recent publication arguing exactly that for Deinonychus.

Morphological Variations within the Ontogeny of Deinonychus antirrhopus (Theropoda, Dromaeosauridae)

[Deathadder]

"Ho"?

And thanks for sharing.

[Cross]

Jun 26, 2015 19:22:25 GMT 5 blaze said:

ho, there is a recent publication arguing exactly that for Deinonychus.

Morphological Variations within the Ontogeny of Deinonychus antirrhopus (Theropoda, Dromaeosauridae)

Wow. Why didn't anyone tell me that blaze was a sassy African American woman?

"Ho, I'm tellin' ya. That Deinonychus specimen in the musem was damn fine. Mmmm-hmmmm. *snaps fingers in a Z-movement*"

[blaze]

hahaha sorry, I'll remove it, I was thinking in Spanish back then, it was meant to be a short evil laugh (jo jo jo in Spanish sounds like ho ho ho in English) but I forgot that ho is an slang term for prostitute.

[Cross]

That's alright. I found it pretty funny anyway.