T. Rex Bully

T. Rex Bully

The fictional scientists in the movie Jurassic Park had the opportunity to observe living, breathing dinosaurs on their remote island. But real-life paleontologists can learn about the behavior of dinosaurs only by examining the fossilized bones they left behind. An exhibit opening in London pulls together this evidence to paint a very different picture of Tyrannosaurus rex.


Was T. rex a hunter or a mugger? I'm Bob Hirshon and this is Science Update.

Of all the dinosaurs, Tyrannosaurus rex is generally seen as the most ferocious hunter. But according to a new exhibit at London's Museum of Natural History, that's a misconception.

The exhibit was organized by Jack Horner, curator of paleontology at the Museum of the Rockies in Montana, and consultant on all three Jurassic Park films. He believes T. rex was more of a schoolyard thug that muscled in on the kills of real hunters. That's because its clunky legbones and stubby arms were ill-equipped for chasing and seizing prey.


So here we have an animal that can't run, can't grab, and has bone-crushing teeth. Also has huge olfactory lobes for distance smell. So the evidence leads to a better conclusion that T. rex was a scavenger rather than a predator. It'd be kind of a big nasty, stinky bully.

But don't take his word for it. At the museum, visitors are encouraged to judge the evidence for themselves, and even argue with the scientists in charge.


That's what the exhibit is for—is showing how science works. And allowing the public to actually interact with it—to evaluate the evidence on their own.

For the American Association for the Advancement of Science, I'm Bob Hirshon.

Making Sense of the Research

Just because something is widely believed doesn’t make it true. This applies not only to popular misconceptions (for example, that tomatoes are vegetables rather than fruits), but also to scientific ideas.

The belief that Tyrannosaurus rex was a predator has long been dominant not only in movies and popular legends, but even among scientists. Why? Well, according to Horner, it's mainly because it looks scary. T. rex has huge teeth and an enormous head. Standing 16 feet tall and weighing about 12,000 pounds, it was certainly among the largest and most fearsome of the dinosaurs. So many people, including Henry Fairfield Osborne, the paleontologist who named the animal, simply assumed it was a predator. You certainly wouldn't imagine it foraging for nuts and berries.

But as Horner points out, there are a number of pieces in the "predator" puzzle that don't quite fit. Predators have to chase down prey, and prey animals can usually run pretty fast (think rabbits and antelope today). So it would follow that a top predator could also run fast. But when you look at a T. rex's legbone, it has a long thigh bone and a short shin bone. The reverse is usually true among the animal kingdom's best runners. In fact, the legs of a T. rex more closely resemble those of a human—and we're on the slow side by animal standards.

Once you catch your prey, you've got to grab it and hold it down. Take a good look at the arms on any realistic drawing of a T. rex. They're almost comically short and puny. Can you really rip apart an Apatosaurus with arms like that? Horner doesn't think so. Finally, true predators like Velociraptor (the really nasty one from Jurassic Park) usually have sharp, flesh-cutting teeth. T. rex had big, round, bone-crushing teeth, better suited to cleaning someone else's plate than digging into a fresh kill.

In short, Horner sees T. rex as the dinosaur equivalent of a big bully who never brings his own lunch to school, but beats up other kids and steals theirs. A T. rex that happened upon a group of hunting dinosaurs would have no trouble muscling in on their meal, thanks to its enormous size and powerful jaws. Why wear yourself out hunting when you can have someone else do the hard work for you? The T. rex's powerful sense of smell would have certainly helped it track down the best party to crash.

There are many other instances in which scientists have made assumptions that turned out to be flawed. The Greek scientist and philosopher Aristotle wrote that men had more teeth than women without bothering to check; he was wrong, but his belief went unchallenged for centuries. Accomplished scientists also once assumed that the earth was the center of the universe, that insects could materialize out of thin air, and that no animal other than humans had a complex social system—all of which were eventually disproved by careful inspection.

Now try and answer these questions:

  1. What evidence suggests that T. rex was a scavenger, rather than a predator?
  2. Imagine that you were trying to test this idea further. What other kinds of evidence would you look for that might support or disprove your theory?
  3. Can you think of an assumption you made in everyday life that turned out to be untrue? What made you challenge that assumption?
  4. Now think about ideas you have learned about in science classes. Which of these challenged assumptions that someone might make from casual observation? What evidence supports the theory that challenges the assumption?
  5. Can you ever make assumptions in science? Under what circumstances? When are assumptions necessary in order to test an idea?

For Educators

The London Museum of Natural History has an online component to the T. rex exhibit.

T. Rex: Scavenger or Predator?, by the University of California, Berkeley's Museum of Paleontology, addresses Horner's question.

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