An automated Tyrannosaurus rex during the world preview of the Walking With Dinosaurs - The Live Experience show in Sydney, January 2007. Experts are continually reviewing the picture we have of the dinosaur as they gather more evidence.
Credit: AFP
SYDNEY: Turns out T.rex was no ballerina, but was a plodding giant with a turning speed equivalent to a fully laden bus, according to a new study.
As thrilling as it was to watch the species at its fleet-footed best in the 1993 movie Jurassic Park, the reality is "T.rex couldn't chase down a jeep, and would have a hard time out-manoeuvring a human," said John Hutchinson, co-author of a new study, and expert on biomechanics at the University of London's Royal Veterinary College in England.
In 2002 Hutchinson and his team used biomechanic computer models to reveal that the carnivore likely ambled – rather than sprinted – towards its prey.
They now report in an upcoming Journal of Theoretical Biology that T.rex was even heavier than thought, and consequentially found it hard work to turn while moving.
Can't catch a jeep
To aid in their analysis, Hutchinson and his team designed computer models in 3-D, which take the bare bones of fossil skeletons and add virtual flesh to them. These models were created by studying the musculature and movement of ostriches – the largest living descendant of the dinosaurs and bipedal land speed record holders capable of clocking up speeds of 65 km/h.
Previous estimates weighed an adult Tyrannosaurus in at three to four tonnes with a top running speed of 40 km/h – but with new, more accurate models the researchers argue that the average adult would have weighed as much as six to eight tonnes.
"A really big individual might even have weighed 10 tonnes," said Hutchinson.
This hefty mass would not have helped with mobility. The huge inertia – or resistance to turning – caused by a heavy head and tail far from the animal's centre of mass, would have made changing direction difficult.
It would probably have taken one to two seconds for the animal to turn only 45°, said Hutchinson – an amount that humans, being vertically oriented and tail-less, can spin in just fractions of a second.
Fatal flaw
The study "raises the bar on how dinosaur biomechanics should be done," commented Stephen Gatesy, a biologist from Brown University in Rhode Island, USA. He says the work brings scientists closer to answering big questions, such as whether T.rex was a hunter or a scavenger.
"This strikes me as the most sophisticated analysis of the body mass, body mass distribution, and implications ... for the locomotion of T.rex to date," said Jim Farlow, a geoscientist at Indiana University in Fort Wayne. According to Farlow, the find suggests that large adult T.rex probably didn't attack smaller, more agile prey – but went for larger, lumbering dinosaurs instead.
Hutchinson concurs, adding that the hefty duck-billed Edmontosauraus or the horned Triceratops would have been more likely to end up as T.rex lunch than small, fast animals.
Although T.rex could potentially manage a leisurely jog, it was better off not trying, since any fall could be potentially fatal. When a creature the size of a Tyrannosaurus topples over, "It hurts itself badly and may even die," said Farlow.
T-rex arms
So if T-rex was too slow to catch anything, that makes it a scavenger.
But surely having arms would be useful as a scavenger to rip apart dead things. How come T-rex had such pathetic little arms?
What big teeth you have Mr Rex....
Guess it didn't need strong arms with teeth like that.
Not a scavenger
The scavenger card has been tried, the enormous size of the head and design of the teeth say otherwise. Most scavengers have smaller straight teeth vs the hooked slashing monsters of the T.Rex. There was no suggestion that the prey was faster or more agile as they had similar weights and had 4 legs. A perditor always chases the slow and weak, animals not known for their speed T.Rex was a killer
Likely both a hunter and a scavenger
Bears do both. They can smell food from miles away, and track it down. But they also hunt their range. And when possible they'll ambush. If they wander across a "herd" they'll go after the weak (the young, the very old, the crippled, the ill). They will rob smaller hunters if necessary. In short, they don't have to be fast, but are capable of short bursts of speed.
Same with big cats. Lions and tigers are excellent at ambush tactics. There is currently a debate about whether or not T-Rex functioned in a family unit. A collection of fossils discovered a few years back hinted of a female, a smaller male, a "teenager" and a very young T-Rex all found relatively close together suggesting a family unit. If and when more such groupings are unearthed, time will tell if more such evidence appears.
After all, some cats hunt co-operatively and some are solitary hunters. Some-one will study the various T-Rex hunting grounds and possibly discover that prey abundance determines group vs solitary hunting. If T-Rex hunted triceratops (known to move in very large herds) I'd have to think that a T-Rex family unit of co-operative hunters would have the best chance of culling the herd. Triceratops are thought to circle their young as do Bison today. I can't see solitary T-Rex getting through all those spikes, but it seems reasonable that a family unit of co-operative T-Rex could spook a herd just long enough to separate at least one triceratops before it could get to the "circle".
Behaviorly some hunters are known to hunt co-operatively when meat is abundant, and to hunt individually when times are "lean". These scientists who ignore many possiblities in favor of their one option a needed to generate public interest, but often options are a scientist's best friend. Theorize, look for evidence that both proves or disproves the theory. Don't ignore evidence. Group it statistically. Is the animal a generalist or a specialist? That also is important to the animal's behavior. Generalists use adaptive behavior; specialists usually do not, and often cannot. Which affects what they eat and how they get their food.
Is T-Rex a bear or a lion? Well, what is the herd abundance, and the available cover for ambush?