Puberty Blues for the T.Rex

An anonymous reader writes "A new press release about Tyrannosaurus Rex shows that they lived fast and died young. Growing at 2kg per day for up to 10 years. Links to summaries on BBC and CNN."

Doesn't that seem a bit high?

[cjpez]

I mean, they are the "experts," and I'm just some guy in front of a computer, but what kind of caloric intake would it require to grow 4.6lbs in a day? Was the T.rex a carnivore? If so, you'd think it'd be pretty difficult to kill enough STUFF to be able to do that.

I've been looking around trying to find data on growth rates of other larger animals (elephants were mentioned on the CNN article, and I figured whales may be useful), but all I seem to be bringing up is growth rates in terms of population, not physical weight.

Re:Doesn't that seem a bit high?

[ajax0187]

Fast growth in living organisms isn't that unusual. There's bacteria (with the old example of a single bacteria cell multiplying quickly enough to cover the Earth in a day - under ideal conditions, of course). But even multicellular organisms grow fast, too. Some species of bamboo can grow six inches per day. Giant pumpkins can get 10 pounds heavier each day. In some parts of Alaska, the crops have much less time to grow than in the rest of the country, and yet the produce is HUGE (I'm talking heads of cabbage that are two feet in diameter).

And this holds true with animals, too. A blue whale is only a few hundred pounds when born, but it's weighing a couple tons by the end of its first year. Besides, T-rex was supposed to weigh about eight tons as an adult. Compared to something that big, 4.6 pounds ain't a whole lot.

Re:Doesn't that seem a bit high?

[zantispam]

Which in my opinion implies that it was an omnivore rather than a carnivore.

How, exactly, is a T Rex going to eat plants with six-inch long serrated pointy teeth, hrm?

Lions do the same

[SmallFurryCreature]

As another poster mentioned T-rex was big. Lions are excellent scavengers because they are big. Most predators scavenge if they get the change but it helps if your big enough to scare others away. Being able to claim any food source by your size, wether that food is still runningm, you just killed it, killed by someone else or dropped dead of old age, is a bit of an advantage.

It also works for herbivores. Elephants can be big and smart because they are big and smart. Big enough to stand up to a lion and smart enough to do so. Elephant calves are preyed upon if predators get the chance but elephants got the brains to protect their young. Because their young are so well protected by adults (the whole group helps) they don't need to grow up in a hurry and can therefore use growing energy into growing brains.

Cheetahs on the other hand are excellent hunters but crap at keeping their food or even protecting their young. They are also pretty stupid.

Of course humans would conclude that lions are therefore better evolved then cheetahs. it all depends however on what happens next. Evolution doesn't have an end and it is certainly possible for nature to change enough to make lions the underdog (remove big groups of prey they need and replace with singular small fast prey).

predator vs. scavenger solved?

[cephyn]

To sustain that kind of growth rate, i think that pretty much proves t. rex was a predator first and a scavenger second, and a pretty fearsome predator at that.

Re:Doesn't that seem a bit high?

[MammaMia]

Well let's see. Elephants are born around 200 lbs and reach full size by age 20. Full size females are around 6-7000 lbs and males around 11-13000 lbs. So let's say 10,000 lbs (to facilitate simpler math) over 20 years (assuming steady growth, though it probably isn't) would be 500 lbs per year or 1.4 lb per day? I'd assume more of the growth would occur in the first few years since just about everything grows that way, so it may be more like 3-4 lbs per day in their youth. But I'm just speculating. Draw your own conclusions.

Re:predator vs. scavenger solved?

[MammaMia]

I'm curious how you'd come to that conclusion?

For overall growth you also have to consider activity... wouldn't t'rex burn a LOT more calories hunting than scavenging?? I'd think the info leans more toward supporting the idea of t'rex in all his fearsomeness, chasing away the hunters to move in on their kill.

Coming soon to a theater near you: Predator v. Scavenger! umm...

Re:predator vs. scavenger solved?

[cephyn]

yeah it burns more calories, but the rewards are MUCH higher. otherwise you have to wait for something to die, or be in the right place at the right time to chase someone else off.

I bet t. rex followed a pattern like lions....mostly lazy, but hunt when hungry....and if they happen on something dead, fantastic! bonus!

What evidence is there that TRexes are scavengers?

[TheLink]

Sure the T Rex probably doesn't run that fast. But how fast can one of those huge sauropods run anyway?

Not saying that T Rexs don't scavenge. But why do so many people claim it's a scavenger just coz it can't move that fast? It only needs to move faster on _average_ than the prey. Even if the prey is faster at first, if the prey gets tired first and stops running, it's munch time.

Heck it only needs to bite off a 50kg bit of a sauropod tail every day or so and you should do the 2kg weight gain/day pretty easy, and the sauropod will probably just grow it back - 50kg out of 50 tons is like a 70kg human losing 70g of flesh+blood.

A sauropod could probably seriously injure a smaller predator dinosaur, but it should be harder to keep away a T Rex.

Re:What does that say about T. Rex's mortality rat

[Ayaress]

Other dinosaurs also didn't live long. I've seen estimates that large sauropods didn't live over 30 to 50.

There's another reason they didn't evolve intelligence enough to escape their own destruction, as well. They fell into a lifestyle that didn't require it. Humans became intelligent partially because we didn't really have much else going for us. We weren't fast enough to catch prey, we didn't have furr to stay warm at night or dry in the rain, we didn't have the size to discourage predators or the strength to steal kills from them.

Dinosaurs have other things, though. Sauropods are fucking huge. They don't have to be smart, they're just plain big enough that very few other animals would mess with them. T.rex had its jaws, raptors had their claws and speed, hadrosaurs probably had a herd structure, stegosaurs, ceratopsians, and ankylosaurs had armor and weapons.

Herbivores don't really need intelligence. In fact, they're probably better off if they attack on reflex. The time they take to think things over could get them killed. Instead, like a horse, they see movement in their peripheral vision, and they kick you in the stomach. Good for the horse, bad for an unwary farm hand. Carnivores that have the sort of natural armament that tyranosaurs or raptors had only need intelligence on par with a canine or feline to be successful in hunting. More intelligence means more engergy being poured into the brain and not into other things.