Was the Tyrannosaurus Rex a Hunter or Scavenger?

Here's How Tyrannosaurus Rex Ordered Its Meals

Tyrannosaurus rex

JoeLena / E+ / Getty Images

Hollywood movies have so consistently portrayed the Tyrannosaurus Rex as a swift and merciless hunter that it's easy to forget our images of the ravenous Rexes are mostly a Hollywood invention. Consider the terrifying Porta Potty-chomping speed demon of the first "Jurassic Park." Scientists, however, are less certain about whether the T. Rex fed by hunting or scavenging.

There are two main few reasons so many paleontologists—and so many Hollywood moguls—traditionally subscribed to the fearsome hunter theory: teeth and size. Tyrannosaurus Rex's teeth were large, sharp, and numerous, and the animal itself was enormous (up to nine or 10 tons for a full-grown adult). It seems unlikely that nature would have evolved such a huge set of choppers for a dinosaur that feasted on already dead (or dying) animals. But then again, evolution doesn't always operate in a strictly logical fashion.

Evidence in Favor of T. Rex as a Scavenger

There are four main strands of evidence in favor of the theory that Tyrannosaurus Rex happened upon, rather than hunted down, its food:

  • Tyrannosaurus Rex had small, weak, beady eyes, whereas active predators tend to possess super-sharp vision.
  • Tyrannosaurus Rex had famously small, almost vestigial arms, which would have been nearly useless in a close grapple with live prey. (However, these arms were only puny in proportion to the rest of T. Rex; in fact, they could bench-press 400 pounds!)
  • Tyrannosaurus Rex was not very fast, as it was more of a lumbering lummox than the sleek predator of "Jurassic Park." It was once thought that this tyrannosaur could chase down prey at a blistering 40 miles per hour, but today, a relatively pokey 10 miles per hour seems to be a more accurate estimate.
  • The most convincing evidence, for many scientists, comes from the analysis of Tyrannosaurus Rex brain casts. The brains have unusually large olfactory lobes, which would have been ideal for catching the scent of rotting carcasses from miles away.

T. Rex May Have Been Both a Hunter and a Scavenger

While the Tyrannosaurus Rex-as-scavenger theory has been surprisingly quick to catch on in the scientific community, not everyone is convinced. In fact, this may not be an either/or proposition. Like other opportunistic carnivores, T. Rex may have actively hunted at some times, and at other times it may have feasted on prey that was already dead—animals that had either died of natural causes or had been pursued and killed by other, smaller dinosaurs.

This approach to feeding is common among predators. Consider an analogy from the jungles of Africa: Even the most majestic lion, if it's starving, will not turn up its nose at the carcass of a days-old wildebeest. Many extant carnivores have been known to raid the kills of other meat-eaters if they themselves have been unsuccessful in the hunt.