It is still under debate as to whether the Tyrannosaurus rex was a scavenger or a predator. More recent literature written by Jack Horner depicts the dinosaur as an obligate scavenger meaning it would kill and also scavenge for food. One indication of scavenger behavior is that the Tyrannosaurus rex had a great sense of smell from enlarged olfactory bulbs and nerves similar to vultures of today. Because their teeth were capable of biting into bone, it is possible that the Tyrannosaurus rex used this adaptation to get at the marrow of the carcass when that was all that was left. In addition, the tiny little arms of the Tyrannosaurus rex were probably not very helpful in the acquisition of live prey. The imposing jaws and outlandish neck muscles were most likely best used to fight away any competition over the already dead carcass.

By examining the skulls, it has been determined that the Tyrannosaurus rex had the stereoscopic vision seen today in humans, owls, cats and hawks. Stereoscopic vision allows for depth perception, a common trait seen in predators. Animals that have eyes on the sides of their heads are usually prey or scavengers and these eyes allow them to see if a predator is approaching. This dinosaur may have relied on a hunter method similar to that of the slow Triceratops and duck-billed dinosaurs. Tyrannosaurus rex may have also liked to select weak individuals as prey like the modern Sharks and Komodo dragons. Many modern predators rely both on scavenging and active hunting for food. It is very likely that the Tyrannosaurus rex would wear out its prey after a surprise bite when possible and sometimes eat food already killed.