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1 ^ l and bit into a live adult Tricer-atops as it did in the flip drawings on the facing pages, but I doubt it happened. Even though T. rex's upper teeth were rounded and seven inches long and do look like they could puncture things, the teeth in the lower jaws were smaller and more knifelike. And all of the teeth, upper and lower, have serrations for cutting flesh. I don't think they could crush the bones of a struggling beast. In this scenario, I can imagine T. rex losing some of his teeth in the back of a Triceratops. I think T. rex was too big and heavy to wrestle around with its prey, delivering bite after bite, the way it did in the movies. If a T. rex fell over, it would take a while to get back on its feet, and its prey would be lost.

Maybe T. rex shook prey to death. Bob Bakker suggests that the braincase of T. rex had lots of room for the attachment of flexing neck muscles. These muscles might have allowed tyrannosaurs to shake their prey violendy.

Still, I find it hard to imagine a single bite and a few shakes, even from a T. rex, killing or even crippling an animal the size of a Triceratops. Maybe T. rex's teeth could puncture some bones, but I don't see how they could puncture a Triceratops femur. We do occasionally find grooves on the bones of Triceratops that look as if the teeth of a carnivore scratched the bone. I've seen puncture marks on a Triceratops femur that were big enough to have been made by a T. rex. But they are on both the upper and lower surfaces of the bone. To get its mouth around the big leg bone like that the T. rex would have had to have been eating an animal that didn't move—in other words, a corpse. However, Ken Carpenter has a tail bone of a duckbill with puncture marks he thinks come from a T. rex. Several spines of the animal's vertebrae were mangled and grew back, so maybe that duckbill survived a T. rex attack.

Maybe it lived only to die a more painful death from T. rex's bite days or weeks later, if you buy Bill Abler's notion of T. rex, the infector-killer. Bill Abler is a Chicago researcher on tooth structure in dinosaurs. He thinks T. rex infected its victims with bacteria stored in the pocketlike gaps between neighboring serrations in its teeth. Wild as that may sound, it isn't unheard of in the animal world. Komodo dragons, the largest living lizards, grow to nearly ten feet long on the Indonesian island of Komodo. They aren't just big, they're nasty. They will attack animals as big as water buffaloes. Their teeth look somewhat like T. rex's—curved spikes with long rows of serrations on the back edge. But Komodo dragons' teeth are hollow, and their tooth serrations resemble those on leaves, not cubes like T. rex's serrations.

Still, Bill Abler thinks Komodo dragon teeth were enough like T. rex's that T. rex may well have killed as Komodo dragons do, by dropping fetid grease and meat particles from their serrated teeth into the tissue of their victims. (Who knows, maybe they had poison glands, too, as do the dinosaurs in Michael Crichton's Jurassic Park.)

Before arriving at his novel conclusion, Abler actually went to elaborate lengths to test the cutting action of tyrannosaurid teeth. He built steel blades with different dimensions and serrations. He found T. rex teeth had

komodo dragons are among the largest coldblooded killers on land today. they kill by infectious slobber and have been known to consume humans.

BILL ABLER HAS STUDIED THE teeth of many carnivores, living and extinct and has drawn some interesting conclusions.

more in common with smooth dull blades that act as simple spikes than with hacksawlike serrated blades that grip and rip meat. To grip and rip required coarse serradons like those on the much smaller teeth of the man-sized dinosaur predator, Troodon.

As blades, T. rex teeth were only marginally efficient. The spaces between neighboring serrations caught and held bits of meat. These chambers could, Abler reckons, have been "havens for the bacteria with which tyrannosaurids infected and subdued their victims." And since T. rex's teeth weren't quite razor-sharp cutters or steak-knife tearers, maybe slow debilitation by poison or blood loss was its best means of weakening a victim. Phil Currie disagrees. "Backed by the strength of its jaws and the weight of the skull, T. rex's teeth are perfect weapons for cutting, processing, and ldlling."

But maybe T. rex did kill, with help. We usually assume T. rex was solitary because we haven't found more than one T. rex at a time. But we haven't found enough T. rexes to say anything knowledgeable about

the animal's social life.

Cooperative hunting, like that in wolf and dog packs today, is associated with pretty high intelligence. But animals a lot less smart than wolves, or T. rex for that matter, can hunt together. Some lizards today hunt cooperatively.

Again, we have no hard evidence of cooperative hunting by any dinosaurs. We do have plenty of fossils and trackways to show that plant-eating dinosaurs traveled in huge herds. Bob Bakker believes T. rexwas a pack animal since some footprints seem to show smaller meat-eating dinosaurs moving in packs. But those marks are from animals a lot smaller than T. rex, and could just as easily be left by one or a few animals repeatedly patrolling along the shore.

What makes more sense to me is that perhaps T. rex was a scavenger, at least a good percentage of the time. Scavengers aren't stupid, either. Though he saw T. rex as a killer, Barnum Brown also wrote that the braincase of T. rex "shows a well-developed fore- and hind-brain and abnormally large olfactory lobes. This would indicate that some of the carnivorous dinosaurs at least, depended heavily on their sense of smell when searching for food, and that they were carrion feeders as well as killers."

Life can be simpler and more efficient for scavengers, especially when there are lots of prey animals around. It appears from the number of fossils we've found that Triceratops ranged in huge numbers where we find 71 rex. That means herd animals died from old age, disease, or disaster in big numbers too. If so, T. rex didn't have to kill anything on the move. Its meals were already dead.

Or perhaps T. rex took down only sickly animals. Scavengers today have a tough time finding enough food in many environments, but in T. rex's day there would have been a good supply of the dead and dying from the huge herds of horned dinosaurs. Even if T. rex were a good hunter, why should it have spent expen-

wolves hunt cooperatively. perhaps some dinosaurs were smart enough to do so as well. but I don't imagine t. rexes doing so.

tyrannosaurids scavenging a meal. all carnivores, no matter how efficient they are as hunters, scavenge as well.

sive energy chasing healthy, live animals when there was plenty of free food to be had?

T. revasascavengerisn'tanew idea. And it isn't a popular one.

For much of this century, scientists thought T. rex was a scavenger. But that's when we viewed all dinosaurs as stupid, sluggish, and swamp-bound.

It goes against our prejudices that anything so frightening would not have been a killer. And T. rex as a scavenger is unappealing because people think of scavengers, wrongly, as being low on the evolutionary totem pole. We think killers are special and scavengers are slow and stupid. Picking over carcasses is not a behavior we approve of, though we make a party of it every Thanksgiving. The animals that do scavenge, such as vultures, aren't well liked. I think they're graceful myself. But don't think of T. rex as a vulture. Think of it as a bald eagle. Bald eagles are mosdy scavengers, too.

Scavengers can be fierce as well as clever and alert—they do have to defend their carcasses once they've found them. They can use a big, strong head like T. rex had, to process food. And scavengers can better afford the weight of a huge head than can a pure predator, which would need to be more agile to capture its dinner.

I'm not convinced T. rex was only a scavenger, though I will say so sometimes just to be contrary and get my colleagues arguing. And I'm not the only scientist who sees T. rex as a part-time hunter at most. Another is Jim Farlow. He thinks T. rex, like most meat-eating dinosaurs, was a scavenger that also killed when the opportunity arose. Jim is a cautious scientist, but he's not being just a fence sitter. The way Jim sees it, T. rex was tall and had good eyesight, and so could have seen carcasses miles away in forested country. And carrying its head several feet off the ground, T. rex could catch an early whiff of the fragrant (to T. rex at least) odor of rotting Triceratops, since wind speeds increase with altitude, even heights as modest as twelve to fifteen feet. If it came across such a carcass, T. rex would have been happy to scarf it up.

On the other hand, attacking a full-grown, long-horned Triceratops might have been a good way for T. rex to become shish kebab. But a sick, old, or injured Triceratops would certainly be fair game. Such weakened animals are the prey among herd animals hunted by many of today's big predators, from lions snaring a baby zebra in the Serengeti to wolves surrounding a sick moose in the Arctic.

Think about the Serengeti for a moment. You've got huge migrations of animals, and thousands of animals dying while crossing rivers, or in floods or droughts. In T. rex's world there were ten thousand, maybe a hundred thousand, horned or duckbilled dinosaurs moving around in herds. Some must have died in just the same way the wildebeest do now. What's going to eat those corpses? If T. rex isn't, who the heck is? Talk about a missed opportunity: if T. rex wasn't a scavenger then, it would have been very strange. Maybe T. rex didn't like rotten meat, but I find that hard to imagine. I don't know any carnivores that picky. Ever see what a dog will eat? It doesn't matter how many weeks the meat's been lying around, not to my dog, at least.

What about all those scratch marks and broken bones on Sue? What do those tell us? Wasn't T. rex fighting prey? T. rexes could have busted up each other fighting for carrion, or for mates. Crowded together, battling over a corpse was a good reason for tyrannosaurs whomping each other, stepping on each other's tails and breaking them. A foot bone of the T. rex at University of California, Berkeley, is all screwed up as though it got stepped on and rehealed. If "Sue" were a predator, how would it have gone out and gotten food

while all those broken bones were healing? A crippled scavenger might have had a better chance of surviving while it was on the mend.

In the end, to me, this whole preda-tor-versus-scavenger debate is a red herring. Most carnivores aren't fussy like us about where they get their meat, whether from dead animals or live ones. Hyenas are scavengers but they don't think twice about killing for lunch, even their own family members. They are opportunists. Among backboned animals, only airborne carrion-searchers like vultures and condors are pure scavengers. The rest take whatever easy pickings they can find, dead or alive. To my mind, T. rex was simply the greatest opportunist of them all.

We're lucky to have the opportunity to know T. rex, study it, imagine it, and let it scare us. Most of all, we're lucky T. rex is dead. And we're not.

vultures get bad press. they are elegant, successful animals.

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