So... T REX

[Comrade Tortoise]

So, what T REX a hunter or a scavenger?

I will throw my weight around once there are votes

[Hedgecore]

The most likely answer is both. It could hunt with the best of them, but if there's a fresh dead animal lying about, it wouldn't be too proud to have at it.

Also, fun fact: recent fossil records show the T-Rex had feathers.

even more fun fact: last year a T-Rex bone was found containing actual, non-fossilized, soft tissue inside it. woah.

[Mayabird]

The most likely answer is both. It could hunt with the best of them, but if there's a fresh dead animal lying about, it wouldn't be too proud to have at it.

Also, fun fact: recent fossil records show the T-Rex had feathers.

even more fun fact: last year a T-Rex bone was found containing actual, non-fossilized, soft tissue inside it. woah.

T-Rex with feathers? It'd have had to fossilize in some nice fine sediment for those to show up. I want to see a link first.

I remember the soft tissue story, though. Wasn't it one of the big leg bones? Some scientists were transporting it, and they damaged the bone and realized that soft tissue was still inside it. Naturally the creationists then claimed that the bones had to be only a few thousand years old, thus proving them right.

And yeah, I say both. Most carnivores are opportunistic scavengers, and some of them are also thieves. Lions will steal kills from cheetahs and hyenas, for instance. I can imagine a T-rex bullying smaller predators out of their meals.

[Comrade Tortoise]

I would think that the bullying is the only way that thing got meat.

It was a HUGE animal for one. The only animals it would have found to be a worthwhile meal are animals that live in herds. Herds have many eyes, and prey animals have eyes that are wide-set. At 5 meter tall 15 meter long predator wont be able to stalk prey very well.

Nor could it run. It's legs were not built properly. At best it could power walk. And based upon muscle mass requirements, we could outrun it at a brisk jog.

Also, chasing down hadrosaurs requires a certain amount of jumping over rocky terrain and the like. If T-Rex tried that, it would break it's ribs and break it's face. It would not be able to catch itself when it falls, and chasing down prey, it will fall. And it will die due to being crippled. And even if it survives, tie your hands bahind your back and try to get up from being on your side. It is hard if you are distracted.

Another problem. Tiny optic lobe. Most terrestrial predators have large optic lobes because they are visual predators. Even dogs have keen vision, they just dont see in certain wavelengths. T Rex probably had shitty vision. Now what he did have is a HUGE olfactory lobe. WHich indicates that it used scent. It sniffed out corpses.

[frigidmagi]

We sure they didn't hang in family groups?

[Comrade Tortoise]

As far as I know, we have no way of knowing.

[LadyTevar]

I believe there is a theory that T-Rex may have lived in a small family group of mother and offspring, like the cheetah and leopard do today. Males may have formed partnerships with other males or with their nestmates like cheetah and male lions do.

OT: I am one of the people who think they hunted and scavenged like the hyena and lions do today.

[The Silence and I]

The theory I think fits best is a family grouping where the younger (and thus smaller) members do the chasing/stalking and mommy or daddy wait in ambush with one hell of a bite.

My reasons:

Clearly, a full sized Rex cannot run without risking a fatal fall so solo apex predator is not going to work so well.

Tiny arms do not make for excellent grabbing, although in truth its mouth is thought by some to be more than a trade off, but regardless it still suggests long winded chases are not likely at full size.

Legs change proportions with age--at full size the femur and shin are roughly equal, suggesting it walked most of the time, but when younger the shin was comparatively longer, suggesting a more active sprinter, which fits in well with the idea that the young ones actively hunt for the family.

Eyes are forward facing--sure the optic lobe is not huge, but the creature had binocular vision all the same, you don't need that for anything except hunting. And a large olfactory lobe doesn't hurt your hunting skills either.

Neck is disproportionately powerful, much more powerful than needed to lug around that head. A large Rex could have lifted a small car in its mouth and shook it apart like a terrier shakes a rat. That is the strength used to break the neck, back, or limbs of very large, struggling creatures. For a scavenger it is overkill.

Both upper and lower jaws were very flexible, allowed the Rex to shift its grip, again most usefull when subduing a large, pwerful creature.

The chest cavity is enourmous. Many (but not all) other carnosaurs have smaller chests; in a world of lean chested carnosaurs T Rex was a barrel chested monster. I don't mean the digestive tract was large, I mean the heart was huge, the lungs were huge (in fact, if I recall correctly some of its bones were hollow in the same fashion a bird's are, suggesting air sacks--which mean more efficient lungs). The aerobic powerplant for this creature suggests an active creature that could run, fight, do whatever all day long and not get tired.

And my last bit of evidence for the family group:

They found an old Rex, they think it died in a flood. But the thing is, it had a recently healed broken leg. Something that size, with only two legs to speak of, could not have fed itself like that, yet it lived long enough to heal. The answer that makes the most sense to me is this (they think it was a male) was cared for (read: fed) by its family pack.

Of course without a time machine the correct answer will be a little hazy, but I think I showed why mere scavenger is contested, neh?

[Robert Walper]

I've always taken one look at a T-Rex skeleton, and thought "A scavenger? Riiight...maybe when he was feeling particularily lazy..."

T-Rex's speed always get my attention though.

According to information, a full grown T-Rex had a stride of 12 to 15 feet. Even if the T-Rex could only power walk, it should be able to cover a respectable distance at respectable speeds. For example, if the T-Rez could make one strike in one second (try it, making a normal strike in one second is actually slow), it could cover one hundred meters in just 22 seconds. Or in other words, one kilometer in under 4 minutes. That does not strike me as a slow speed for such a large creature, especially when it's just walking.

While I won't assert such evidence as a fact, the chase scene in "Jurassic Park" always struck me as realistic. Said scene had the T-Rex pursuing a jeep. The jeep did eventually outrun the T-Rex (and at a good clip), but initially the T-Rex over took it and almost got it. And the T-Rex, as I saw it, wasn't running at all, but just taking fast and long strides.

[Comrade Tortoise]

Walper, they actually tested that. It couldnt do it, because if it did, its muscle mass in its legs would be something like 90% of its total mass.

[Robert Walper]

Walper, they actually tested that. It couldnt do it, because if it did, its muscle mass in its legs would be something like 90% of its total mass.

According to this, you're right, but T-Rex could still most likely speed walk.

And interestingly, according to this, Jurassic Park did in fact get the T-Rex's speed right (10-15 MPH). It just looks faster given how they handled and worked the scene.

The verdict, as you heard, was that T. rex was pretty pokey. 10 to 25 miles per hour isn’t slug-like, but it’s in the same ballpark as a top human runner (15 miles per hour) and nowhere near the fastest modern animals (cheetahs, for example, can run 70 miles per hour).

Apparently, even with the relatively slow pace the T-Rex is capable of, it could match a top human runner in speed.

So much for trying to outrun the sucker, although humans should apparently outdistant it.

[Comrade Tortoise]

Apparently, even with the relatively slow pace the T-Rex is capable of, it could match a top human runner in speed.

So much for trying to outrun the sucker, although humans should apparently outdistant it.

Um... the human land speed record is 26 miles an hour.

[Robert Walper]

Apparently, even with the relatively slow pace the T-Rex is capable of, it could match a top human runner in speed.

So much for trying to outrun the sucker, although humans should apparently outdistant it.

Um... the human land speed record is 26 miles an hour.

I doubt many people would qualify as particularily fast, never mind near the speed of world athletes.

[Comrade Tortoise]

you specified top runner though. AVERAGE human might be able to make 12 MPH. But not very easily, and probably only over short distances.

[Robert Walper]

you specified top runner though. AVERAGE human might be able to make 12 MPH. But not very easily, and probably only over short distances.

My bad then, but I was quoting the article here:

The verdict, as you heard, was that T. rex was pretty pokey. 10 to 25 miles per hour isn’t slug-like, but it’s in the same ballpark as a top human runner (15 miles per hour) and nowhere near the fastest modern animals (cheetahs, for example, can run 70 miles per hour).

[The Silence and I]

Reading that article I have to wonder: why is this a death blow to a predatory T Rex? Its normal prey also fell into that speed range! At that size everything was slower, not just the Rex.

Add in family packs and it gets even better, the young were lighter and had relatively longer legs. I wonder why...

Slightly off topic: I was surprised by this bit:

To overcome the number of unknowns in the model, such as the penetration angle of muscle fiber, Hutchinson and Garcia changed unknown parameters to determine what effect they have on the results. Andrew Biewener of Harvard's Concord Field Station complimented the authors for this use of sensitivity analysis, in an accompanying article in Nature. Using this technique, Hutchinson and Garcia discovered that most of the unknowns did not have a significant effect on the outcome, except they did find that the limb orientation made a significant difference in the model.

"A Tyrannosaurus needs a lot more muscle mass to run quickly if it used a crouched pose than if it used a more columnar pose. But in either case, we felt we could rule out 45 miles per hour running. It required too much muscle mass," Hutchinson says.

The way this is worded suggests the researchers were not sure that a croutched leg orientation would make it harder to run until they tested it! It's things like this that make me wonder sometimes...

(Look at the thigh of most birds today, it is sort of horizontal, which is why it is easy to confuse the ankle for the knee--you can't see the knee unless you remove the feathers. With such an orientation the bird needs more muscle mass just to stand without tiring, running requires much more muscle. Try it yourself, hold your thighs as horizontal as you can and run/walk around the room for a while, see how long you can last before keeling over )

[Elheru Aran]

For all they're built like that, chickens are damn fast. Trust me on that.

[The Silence and I]

Chickens and most birds are light enough that it doesn't make a huge difference. Oh, and I believe you, I've chased them before

Something I forgot to mention before: teeth. T Rex had long, railroad spike style teeth which coupled with a 3000 lbs per square inch bite seem more suited for wreaking havok on a spinal collumn than tearing away dead flesh. They are comparatively straight and not very sharp, with little serration along the back edge. These are teeth that have the potential to kill a large animal very quickly by severing the spinal cord/breaking the back/neck.

[frigidmagi]

So it would be designed around a one bite kill? Could it be an ambush attacker?

[Robert Walper]

So it would be designed around a one bite kill? Could it be an ambush attacker?

I suppose this would depend on the visual acuity of it's typical prey and it's available cover to hide it's presence.

Any ideas on what kind of enviroments the T-Rez normally operated in, and if they provided routine opportunities for ambush for a creature of it's size?

[Comrade Tortoise]

So it would be designed around a one bite kill? Could it be an ambush attacker?

I suppose this would depend on the visual acuity of it's typical prey and it's available cover to hide it's presence.

Any ideas on what kind of enviroments the T-Rez normally operated in, and if they provided routine opportunities for ambush for a creature of it's size?

Lightly wooded grassland. Not much cover.

OK. What do we know about Adults

Adults are large barrel chested specialized walkers. They could power walk for SUSTAINED periods, and possibly run at 15 MPH (however this mode of locomotion would have been risky) Tey had railroad spikes for teeth. Bone crackers, as opposed to bone crushers. It is the difference between breaking a spinal column, and pulverization. One is usefully for quick kills, the other is usefully for ripping off chunks of flesh covered bone. They had binocular vision, but with relatively low processing power compared to their olfactory bulbs. This indicates not so much that they ahd bad eyesight, but rather that they are much more reliant on scent. Size and efficiency of brain structures is often changed over the course of an organism's life through use, though there are limits to this. For example, a person goes blind. Their optical lobe will be rerouted to assist in touch, for example. There is evidence of massive healed infections and non-leg bone breaks. This suggests that they were capable of sustained combat. Probably not with other species, but wihin theirs.

Now for the Juviniles. Barrel chested, and their femur was longer than their tibia. WHich means they could run faster than the adults, and could so so for a long distance. Fast jog to a run. They had the same type of teeth. I dont think their are any braincase scans.

Also, there is evidence of pack behavior.

What this tells me, with their capacity for sustained activity is that they moved constantly, in groups. Now there are really three distinct possibilities here.

The first is that the small ones chased prey into the waiting eyes of an adult. The does not work because there was not enough cover for said adult in their environment.

The second is that they were social scavengers. Following herds of hadrosaurs and taking over the kills of smaller predators. This is a distinct possibility. It works with the evidence fairly well, but it does not explain why they have bone cracking, rather than bone crushing teeth.

The other possibility, is that they act like african wild dogs as far as hunting is concerned. The young ones chasing the herd at a moderate pace until a weaker herd member tires. This member would then be singled out, and taken down by the younger animals. The adult would either be the one to teach the younger how to kill much like adult lions do, or perhaps they help hold territory and ward off other predators with their size. Acting like male lions.

[The Silence and I]

I prefer the last one, CT. The size of the adults, and the evidence of inter-species combat suggests to me the adults acted as the male lion does today; he doesn't hunt, but he does protect the pride from other threats. Adult Rexs could have acted in this way.

One other thing, as I recall it CT, the tibia is longer than the femur in the young (the two are roughly equal in adults). You have the order mixed up, I think (a longer femur indicates even slower gait, it makes speedy running nearly impossible at any mass).

So it would be designed around a one bite kill? Could it be an ambush attacker?

CT addressed the ambush I think, but yes, it's skeleton indicates it was built around delivering one hell of a powerful bite, followed up with violent neck movements, with the intented goal being to snap tendons, spinal cords, ligaments, and pierce and shatter bone around the spinal area. One bite, one broken back/neck, one hopelessly crippled and dying victim.

[frigidmagi]

That would certainly reduce the chances of a grapple, which I think anything with arms that tiny would want to avoid.

[Mayabird]

Any ideas on what kind of enviroments the T-Rez normally operated in, and if they provided routine opportunities for ambush for a creature of it's size?

Lightly wooded grassland. Not much cover.

Would it have been grasslands for the entirety of T-Rex's existance? I thought that grasses only evolved and began to diversify towards the end of the Cretaceous and became far mroe prevalent afterwards. I know that grasses were found in fossilized dinosaur feces, but those were towards the very end, around 67 million years ago.

[Comrade Tortoise]

One other thing, as I recall it CT, the tibia is longer than the femur in the young (the two are roughly equal in adults). You have the order mixed up, I think (a longer femur indicates even slower gait, it makes speedy running nearly impossible at any mass).

yeah, I mixed up the order

Would it have been grasslands for the entirety of T-Rex's existance? I thought that grasses only evolved and began to diversify towards the end of the Cretaceous and became far mroe prevalent afterwards. I know that grasses were found in fossilized dinosaur feces, but those were towards the very end, around 67 million years ago.

Well, grassland-like. I suppose you could call it thinly forested scrub.