Scientists have recently started developing arguments for the point that the Tyrannosaurus rex was not a predator. The dinosaur was always considered a predator, but recent research suggests that the T-rex could have been a scavenger. Paleontologist Jack Horner of the Museum of the Rockies proposed the argument that the T-rex could not have been a predator. Possible arguments Horner has discussed are the small eyes (needed to see prey), small arms (needed to hold prey), and huge legs (meaning slow speeds). Evidence that supports HornerŐs theory is the large olfactory lobes (part of the brain used for smell) that the T-rex had. Vultures also have large olfactory lobes and are scavengers. Other scientists argue against HornerŐs theory and fully believe the Tyrannosaurus Rex was a predator.

The dinosaur that roamed the Earth 65 million years ago is considered a type of reptile, meaning they are cold-blooded. Recent research conduced be paleontologist Reese Barnick and geochemist William Showers report that the Tyrannosaurus rexe's temperature is uniform throughout its body. The T-rex was maintaining a body temperature in its core and extremities, that varied by 4 degrees centigrade or less, which means it was homeothermic. Homeothermy is a sign of a warm-blooded animal, which removes the T-rex from the reptilian class. Other scientists argue that the dinosaurs were warm and homethermic because they were big, not because they had high metabolism, which would also suggest a warm-blooded animal.