Carnivorous dinosaurs have a reputation of being voracious predators. However, rather than chasing down helpless prey, new research suggests that meat-eating dinosaurs may have been expert scavengers, much like hyenas are today.

Unlike the monstrous Tyrannosaurs rex and Velociraptor of "Jurassic Park," scientists from Trinity College Dublin have shown that many of these extinct prehistoric predators would be better remembered as oversized, scaly or feathered hyenas.

Their study revealed that scavenging, or feeding on already dead material, would have been a particularly rewarding strategy, as it simply requires less energy.

Even modern-day lions, for instance, scavenge nearly 50 percent of their food in some locations. The only difference is that the body sizes of meat-eating dinosaurs varied greatly, and often times, their prey were larger.

Using computer simulations, the researchers modeled what the Mesozoic environments would have been like between 252 and 66 million years ago. This allowed them to paint a clearer picture of how meat-eating dinosaurs lived and foraged.

Maintaining a balanced energy budget presented a major challenge for theropods, which ranged from the chicken-sized Microraptor up to the whale-sized Giganotosaurus, in the face of intense competition and the demands of growth.

The researchers' models revealed that the most efficient scavengers would have been species weighing roughly half a ton, such as juvenile T. rexes or the mid-sized Dilophosaurus and Utahraptor.

"In effect, these species occupied a Goldilocks zone. They were big enough to search large areas in order to find carcasses and defend them, but not so large that simply moving became too energetically costly," explained Kevin Healy, co-lead author of the study and research fellow in Trinity's School of Natural Sciences.

However, the researchers also confirmed that carnivorous dinosaurs could not have survived on scavenging alone. Therefore, the large predators must have also hunted for food.

"Our results also confirm that scavenging alone was unlikely to be a successful strategy in meat-eating dinosaurs and that practically all species would have likely shown predatory behavior," Healy added.

While these findings don't necessarily soften the T. rex's iconic image, they do shed new light on the life of Earth's ancient rulers and how the behaviors of dinosaurs may have been similar to those of modern animals.

The study was recently published in the journal American Naturalist.