Was Tyrannosaurus a predator or scavenger?

But think: its prey is - at best - on the same transmission system. Duckbilled dinosaurs aren't going to whizz about and do a Charles Johnson when they see the tyrannosaur coming, and especially not them, since they're not even ornithiscians. Lizard-hipped means slow going. T. rex's locomotion was probably more than adequate to get after one of them. As I recall, ceratopsians for example are reckoned to be much slower. If everyone else is driving Mazdas...the Topaz is king.

Not necessarily - the large flightless killer birds of about 10 MYA (the "terror birds") probably used their bite and talons both. And T. Rex had a balancing tail to flick. I'll bet they could have been a bit more creative if they had to.

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They worked it out against the Serengeti and the 40,000,000 kg of ungulates that apparently die there each year. Can't post the PDF unfortunately; but this is a big, big assumption.

http://www.journals.royalsoc.ac.uk/content/656v56hlp46nqk4w/

Unfortunately I can't post the PDF, but they explicitly talk about reptilian activity schedules and allometric energy relationships from page 731 (the first page) onward. They did mention the mammalian model in the article (avian would have been the correct one) but then essentially said that increased average moving costs would have been offset by more inactive time between kills, which is kind of cheating, really. Why aren't the reptilian-model T.rexes then also resting more between kills? No idea. Silly.

I agree, naturally - it's just that wolves (even though they're not the biggest carnivore around) are predators mostly, and scavengers whenever they can. I've no doubt that T. rex scavenged too - just not primarily.

 

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Anything in the Felidae. Various Ursids.

 

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I agree they weren't particularly fast, but as I recall it was always suggested it would be enough to outrun a T-rex(seeing as they have no other defenses I'd like to think they were fast enough to outpace a predator), it would require a quick short burst most likely from an ambush to catch one, seeing as Hadrosaurs kept to herds it's likely a T-rex would be spotted unless well hidden, although I consider it likely and plausible a T-rex would attempt it, it certainly isn't easy.
This is one of the reasons I consider it to be both scavenger and hunter, if it were to hunt, a Hadrosaur would be the most likely prey.

There are a lot of factors in speed, don't forget both T-rex and Raptors were lizard-hipped, and I'm quite sure Raptors had good speed, whilst the Hadrosaurs were bird-hipped.
Adequate speed perhaps, given the circumstances.

Can't say I'm at all conviced it would be at all balanced, 7 tons leaping onto a dinosaur? Raptors likely leapt, using their comparitively longer and slightly winged arms for balance, much like the flightless birds would have done(which were considerably lighter and 2 metres shorter).
I should also point out a flick of the tail will greatly alter the balance of the entire dinosaur. Think of it as counter-balancing weights, if the tail moves left, the dinosaur must move right, if it is leaning the same direction it will topple over, and at that speed do itself great damage.

I'll have a read and see what to make of it. It does sound silly on the surface, obviously dinosaurs were far larger, ideas of comparitive numbers of predators and prey are probably very variable, it just seems an entirely different situation, I could have missed something though.
Interesting to note 40,000,000 kg is 1000 Brachiosaurs.

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There's no single factor that makes me believe it to be a scavenger primarily, more a combination of everything I've covered, though I consider it capable of hunting in some forms(ambushing Hadrosaurs, picking off vulnerable dinosaurs), I consider it reasonable to discount anything resembling regular hunting of large saurapods and well armoured dinosaurs. Having narrowed things down a bit there and looking at it's bodily makeup, likely speed, balance etc I just get the feeling its made to scavenge.

 

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I agree - but they certainly did it. Lions have a hard time hunting herd animals but they still manage. I think this is another argument for a pack structure in T. rex.

I agree it probably did both, but it's really more of a predator to my mind.

Exactly. It's like the old joke about the bear and the running shoes.

I'm not saying it leapt, but that one leg might be used to rend during the kill if the animal had been downed. Though the jaws would probably usually have been enough.

Ah, but the tail is under muscular control. Cats and dogs actively use their tails to maintain balance; a predatory dinosaur would probably do the same. Partial support might also be possible. Not for long periods but I'd be interested to see someone examine the mechanics.

Well, on average the prey of a lion is faster than the lion. Males don't even hunt. Yet no one would ever seriously question a lion's ecological role. Tyrannosaurs were a persistent feature of the Cretaceous; it seems unlikely that the near-largest carnivore of the period would be primarily a scavenger. Wouldn't sauropods and the like simply bloom out to fill all available herbivore niches and eat themselves out of house and home? There's no extant ecological system that I know of with a similar relationship. (One has to discount bears because of their omnivory.)