Re: Lack of Running Giant Theropod Tracksâ

[Sam Barnett <sam.horus@gmail.com>]

"I know there is at least one species of raptor that works together to
hunt rodents, but unfortunately I can't find a video or remember the
name of the species."

That'll be Parabuteo unicinctus - Harris Hawk:
http://www.bbc.co.uk/programmes/p00cjjk5

Cheers,
Sam.

On Friday, December 10, 2010, Sim Koning <simkoning@msn.com> wrote:
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> Augusto Haro Wrote:
>
>>If it took the chest, good. But the torso is short and the legs wouldmove 
>>fast in the worried >predator, so it would not be easy to miss thelegs. In 
>>addition, the target is relatively small if >catchedfrontally.
>
> I think it's worth noting that the head of a Triceratops is rather wedge 
> shaped, which would reduce the likelihood of a straight on collision.
>
>>legs. In addition, the target is relatively small if catchedfrontally. 
>>Anyway, this would be >less of a problem in specimens withthe horns at 90º 
>>from the long axis of the skull. I >do not >trust muchin the capabilities of 
>>the small nasal horn, overall because its baseis so close to >the point of 
>>the snout weakened by the enlargement ofthe external nares.
>
> The snout may not have been as weak as it seemed on the dinosaur documentary. 
> I still maintain that the "experiment" was limited and rather flawed. For the 
> sake of argument, I'll give it the benefit of the doubt however. I don't 
> think the nasal horn would work as a 'primary weapon', but I imagine it would 
> do some minor damage if it contacted flesh during a struggle. I'm guessing 
> every little bit would help in a life and death struggle with a 6 ton 
> super-predator.
>
>>On the other hand, I was yesterday reading that the antelope whichbetter 
>>defends itself from >dhole packs is one with short horns. Thissuggests to me 
>>that relatively short horns are better >when dealingwith predators because 
>>they permit more maneuvrability at close range.
>
> Yes, but a T.rex was a far less maneuverable predator with much greater 
> 'firepower'. A single bite from a Tyrannosaurus rex may been crippling or 
> fatal. Perhaps longer horns that could penetrate the heart and/or lungs with 
> a single blow would have been more useful.
>
>
>>it is posited that both the frilland horns are more likely of use in 
>>intraspecific contest than >fordefense. The frill is also full of superficial 
>>vessels (with apossible thermorregulatory >function), >and some bite directed 
>>at it mayimply dangerous blood loss.
>
> I very much agree that this was one of their primary functions, if not the 
> primary function, but this does not mean that they could not have been very 
> effective weapons for self defense too. We Humans use our legs primarily for 
> locomotion, but they can also make for extremely effective weapons for self 
> defense.
>
>>I said it may be, but phylogenetic bracketing on living forms providesyou the 
>>more parsimonious >hypotheses on the basis of the current evidence. More 
>>parsimonious does not imply more certain. >Many birds hunt animals, not only 
>>raptors, and in most of them no collective organization is >seen. Carnivorous 
>>dinosaurs may have hunted in groups,or not - the last being more parsimonious 
>>>to infer. That they can befound in close association may indicate 
>>gregariousness(orpreservational >bias), as in crocs and many birds, not 
>>necessarilycooperative hunting.
>
>   I think since we now have rather strong evidence that some theropods 
> employed some behavior that was staggeringly similar to some modern birds 
> (such as nesting strategies) we are justified in speculating that many 
> theropods may have had a similar degree of sociality. However I feel it's 
> just as important to understand why it is various bird species are social, 
> and some are not, before we start applying bird behavior to dinosaurs (for 
> the sake of life restoration). For instance, we may not see many pack hunting 
> birds of prey, but this may be due to a limited food supply and the need for 
> relatively large hunting territories. There are some species of birds such as 
> woodpeckers that work together in family groups to gather and store acorns. I 
> know there is at least one species of raptor that works together to hunt 
> rodents, but unfortunately I can't find a video or remember the name of the 
> species. Of course most if not all raptors are also highly monogamous.
>
>>one crocodile, manyend up biting it and thus collaborate in killing it in 
>>practice, butit does >not imply that the intention was to rely in 
>>othercrocodilians, and may just be a case of intended >unique 
>>predationcoinciding with the attempts of other crocs - perhaps the origin 
>>ofcooperative >hunting and cognitive association of these occasions 
>>withsuccess in killing by the individual >predators?).
>
> Good point, I didn't think about that. Of course we do have modern caimans 
> and birds forming creches, and we now see this behavior recorded in dinosaur 
> fossils, so using phylogenetic bracketing to infer behavior certainly has 
> some merit. I also remember seeing alligators working together to form a 
> living fish trap somewhere...
>
>
>>Your example of the bats indicates the dangers of inferring from theRecent 
>>only. But, in lack of >more conclusive evidence either way,parsimony is all 
>>you have.
>
> I think it depends on what behavior we are talking about. Many once thought 
> it was more parsimonious to apply scales to small dinosaurs, which ignored 
> the probability that they were likely warm-blooded animals, and that mammals 
> have hair that evolved for insulation, so dinosaurs may have done the same. I 
> could make the same argument in regards to social hunting: we don't see birds 
> of prey hunting in packs, but they are flying animals, and predatory 
> dinosaurs may have filled niches more analogous to modern predatory mammals, 
> and so may have had analogous behavioral adaptations.
>
>>In any case, it seems that theropods mostlyate young, as many Recent 
>>predators, and thus would >not have requiredgrupal hunting.
>
> This could also mean that the young may have engaged in group hunting as 
> well. Heck, as I suggested with T. rex, for all we know the young may have 
> been pack hunters, while the breeding adults may have been solitary or 
> monogamous. This would be an intermediate between the creche forming of crocs 
> and other dinosaurs, and the monogamous behavior of most modern birds.
>
>
>>Whether the adult ceratopsians did or did not put mucheffort in the defense 
>>of their youngs is >unknown.
>
> There was the Psitticosaurus that was found dead with a creche though.
>
>
>>And, regarding the question "why animals hunt in packs?" as being morehelpful 
>>than invoking >phylogenetic bracketing, I do not see why it isof more 
>>relevance when dealing with the behaviour >of the T. rex.
>
>>Youmay answer that because the prey is difficult to take individually,but 
>>there is the >alternative way to take: do not attack the dangerousprey.
>
>  Triceratops was the most abundant herbivore in a Tyrannosaurus's ecosystem, 
> and we have evidence of an actual battle between the two species; I would say 
> the chances are pretty good that they attacked and killed Triceratops quite 
> often. Many pack hunting predators will grip the head/face of their prey 
> while others go after the throat of guts. The bitten off horn on the 
> Triceratops may be evidence of very similar behavior among T. rex.
>
>
> Simeon Koning
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