T. rex not a 'top' predator, study says

BERKELEY, Calif., Feb. 22 (UPI) -- Tyrannosaurus rex, long held as the "top dog" predator of Earth's dinosaur period, was more an opportunistic feeder than a top hunter, U.S. paleontologists say.

Researchers say that rather than ruthlessly stalking herds of duck-billed dinosaurs and claiming the role of apex predator, T. rex was more likely an opportunistic predator, like the hyena in Africa today, subsisting on both carrion and fresh-killed prey and exploiting a variety of animals, not just large grazers, a University of California, Berkeley, release reported Tuesday.

Paleontologists John "Jack" Horner from the Museum of the Rockies and Mark B. Goodwin of UC Berkeley say a new census of dinosaur skeletons unearthed in eastern Montana shows that Tyrannosaurus was too numerous to have subsisted solely on the dinosaurs it tracked and killed with its scythe-like teeth.

"In our census, T. rex came out very high, equivalent in numbers to Edmontosaurus, which many people had thought was its primary prey," Horner, a professor at Montana State University, said. "This says that T. rex is not a cheetah, it's not a lion. It's more like a hyena."

Normally, Goodwin said, top predators are one-third or one-fourth as abundant as their prey, because of the larger energy needs of carnivores.

Opportunistic hunters like the hyena, however, can be twice as abundant as the top predators.

"If you count the lions and the leopards and the cheetahs in the Serengeti, the number still does not equal the number of hyenas, because hyenas have a much wider food source," Horner said. A hyena will eat "anything else that it can catch or is dead," he said.

Similarly, T. rex was eating anything it could, he said. "There's no evidence that T. rex could run very fast, so it wasn't out there being a cheetah. If it could get a sick animal, it would."